I think this answer is silly. And there is no such thing as the focal length of the human eye, especially not in connection to cameras. This completely disregards the image size we are looking at and the distance of it. And that human vision is very different anyways.
After shooting with 35mm, 50mm and 85mm lenses in my pursuit of finding my perfect focal length for my photography, I had some interesting findings. =50mm seems formal and more strict. And then I found 40mm. 40mm had a true, genuine, real, even a humble feel. I realized that there was something special about 40mm, and seeing this video it makes sense to me why!
It's funny I have lenses ranging from 28 to 40 to 50 to 70 to 85 and 200mm. When I hold them up to my eye on the camera and then look at the object,the lens that matches up best with what I'm seeing with the naked eye is 70mm. 40mm is much wider and further away.
Out of the dozens of sources I've seen cover this topic this is by far the best. The effect of mental focus on your subject and it's effect on apparent subject size is typically ignored completely when covering this topic. I especially liked how you discussed there being one focal length that's closer to the human eye when you are broadly taking in a scene versus a scene where you are mentally focused on a subject, that has an immense impact on the apparent equivalent lens focal length. When I'm not focusing on anything in particular my field of vision is something close to around 18mm but the size of objects within that field of vision appear closer to how a lens around 60mm would make them appear. This simultaneous dual focal length is just not something a camera with a single lens and no brain can recreate so it makes sense to pick a focal range that is a good balance of fov and magnification and call lenses that fall within that range as "normal". Personal preference of fov vs magnification is going to affect what people think is more normal for them individually. I tend to lean toward fov as being more important when thinking about making a scene look more normal but I don't necessarily want subjects to appear too small in the frame so I like focal lengths in the 28-35mm range for representing normal, 50mm cuts off way to much of my peripheral vision to appear normal, even though subject size is closer to normal for me. If I were to average my fov and magnification preference I get 40mm as my average normal which is very close to the original Leica you mentioned. Konica made an excellent Hexanon 40mm f1.8 lens but I'm not sure if there are others.
It turns out the focal length of 43mm was a byproduct of lens design constraints Pentax imposed for the Three Amigos rather than to fit this fact that 43mm on a 135 format sensor corresponds to 1 radian. It's why the other two lenses have 77mm and 31mm as their focal lengths.
This makes so much more sense to me. I've always felt like 28mm or wider is pretty decent at capturing an entire scene like a landscape sort of as I see it. And 50mm is closer to focusing on a detail or a face. Just saying 'this is the focal length' always seemed very silly to me. Thanks for the very detailed video, very educational.
This is why my every day lens on a full frame camera is a 40mm and a 24mm on APS-C. When I put the camera up to my eye, what I see in the frame is pretty close to my generalized perception where I'm just taking in the world writ large without focusing or paying attention to any one thing. If I'm focusing or paying attention to something, closer to 70mm is about right, and 150+ feels like tunnel vision.
I tried this with a Canon 5D and a 70mm-200mm zoom lens... when at 70mm, if you put the camera up to your eye and looked through the viewfinder, everything was the exact same size as when you looked at it with your naked eye, even if the field-of-view is significantly narrower. If you could have a lens with the focal-length of a 70mm lens, but the peripheral view of a fish-eye lens, then you'd have a lens that gives us the same view as a human eye. I think what's happening at the 42mm length is that it's the balance point between the focal length of the human eye, and the wider peripheral view. It's a nice medium that satisfies us just enough on both those factors. If you JUST want peripheral view, then Kubrick's favourite lens of 14mm is probably the way to go to capture that feeling without worrying about size of objects, depth-of-field, etc, being accurate to the human eye. It just gives that "taking it all in" feeling of using your whole field of view instead of focusing on specific objects.
Nice video! Just one clarification: Oskar Barnack never designed lenses. It was Max Berek the genius behind the Leica glass. The 42mm for the UR-Leica was a microscope lens (Summar) that was chosen because it was already available for Barnack's proof of concept. However, they needed a much better lens for the enlargements that were needed to compete with the quality of the prints that were on the market then. The 50mm was easier to design and there were already many examples around to get inspiration from.
I always argue we should not compare photography and human vision in terms of field of view / view angles, but we should compared in terms of perspective, i.e. how we perceive the distance / spacial relationships between the subject and its background surrounding it. That way what we called "normal" lens projects the prospective closest to how we understand the depth relationship in real world is making more sense to me.
I make shows in large spaces round the world we often shoot reference images for the team who arnt on the early trips. The perspective relationship of buildings we might project on is extremely important for designing any sets etc. in large spaces with lots of depth the apparent size of objects always feels most natural to me when shooting near 50mm this really became clear when we were projecting on the Washington monument as there is so much space. When we used 48mm in camera and software our visualisations matched the real world relationships of scale. I’ve never really understood the focus on fov as our perception is so based on building images from many samples and who can really feel the edge of their vision without really focusing on it. How big things are in relationship to each other is how we really feel our place in the world.
yeah I was waiting for this video to get to the perspective part and it just didn't, completely missed a major part of why we consider these normal human vision lenses.
Thank you, haha I threw myself into writing a comment about perspective and then found you comment. Perspective, a natural compression of objects relationship to each other in a 3D space is way more important than field of view for a natural look.
This is for me the most important point, mostly because it has a huge impact on photography and why photographs with big depth differences in the scene always look worse than what you see in real life. YOu can either capture only a very small part of it or the entire scene but with massively skewed spatial relationships. A good paper about this can be found googling "Natural Perspective", which is mostly aimed at rendering but gives some great examples by comparing paintings and photographs of the same scene and how different they look.
I always thought that the "normal" focal lenght was something around 43mm because the diagonal of a full frame sensor is 43.27mm. But this video explains there is more about it. Very interesting, thank You!!
In 1914, the Multi-Speed Company in the United States had a 35mm camera called the Simplex Multi-Exposure which carried a Bausch & Lomb 50 mm f/3.5 Tessar lens. While in Germany Oskar, reportedly had no clue that such a small-format camera was being advertised in the United States (the Tourist Multiple of Herbert & Huesgen premiered in 1914 to a U.S. population as well), 10 or 11 years before his accomplishments with Leica. Therefore, I don't know if back then, could the 50mm lens be a starting point or was the 42mm lens a debatable counter point? Excellent content & insight that you expressed here. I enjoyed it.
In author Douglas Adams’s popular 1979 science-fiction novel The Hitchhiker’s Guide to the Galaxy, toward the end of the book, the supercomputer Deep Thought reveals that the answer to the “Great Question” of “Life, the Universe and Everything” is “forty-two.”
Since the length of the human eye along its optical axis, from the front of the cornea to the retina is approx 24 mm, then I would suggest the focal length is 24mm when relaxed (i.e. focused on infinity), changing by distortion of the crystalline lens to a shorter focal length when focused on a closer object!
Do this experiment; Take a zoom lens on your camera and focus on an object in your room. Lets say a TV from 8 feet away. Put the camera away from your eyes and then put the camera back up to your eyes and continue to adjust the zoom until the magnification matches what you are seeing in the real world. In full frame terms it will probably be somewhere around 65mm-70mm(Lets say it's 67mm). The caveat is that the full frame obviously show a extreme cropped version of what you see in the real world since it's only full frame. If you have the 67mm on a medium format if shows more the the scene and then large format again even more at the same focal length. This is one of the reasons why I hate wider lens for most landscape shots. A 20mm lens on full frame has too much distortion and it doesn't match what I'm actually seeing and even 35mm is too tiny...the only thing the wider lens are doing is letting me see more of the scene at a cost. This is the major advantage of the bigger formats. Ansel Adams for example shot a lot of Hasselblad 6x6 with a 80mm lens but it allows you to see pretty wide at 6x6 compared to full frame. It's also one of the reasons I love Nolan IMAX movies. He's shooting a lot with 80mm lens and the look is distinct from everything else.
Leica actually made a 40mm lens for the Leica CL in the early 1970’s. Rollei and Ricoh, among others, made 40mm lenses for their film point & shoot cameras.
Years ago, when I worked in a camera shop, we used to reference 42-43mm as an "eyeball" normal, meaning the most used "normal" lenses (35mm and 50mm) were somewhere around 8mm wider or 7mm longer than that benchmark. I am currently shooting with a 2/50mm Zeiss Biogon on my rangefinder, which feels that it is really 47mm-48mm - a little wide from what I expected when compared to an old 50mm Dual Range Summicron. In use, I feel a little less constrained than I did with the 50mm. Great video - thanks!
Surveying the landscape of vintage photographic (not cinema) film cameras, I noticed an oddity. 50mm was considered the standard normal lens among 35mm film (i.e. small format, 135 Format) rangefinders and SLRs with interchangeable lenses. As soon as you moved outside of that category, and you start considering medium format cameras, and even fixed-lens small format cameras, the 50mm focal length fixation largely dissipates. A lot of them had 35mm or 40mm equivalent lenses. I mean for example, consider how many Olympus Trip cameras were produced with 40mm lenses! Personally, one of my most-used prime lenses is 28mm on my APS-C camera bodies, which, taking account of the crop factor, works out to… hmm… 42mm! (OK, 42.8mm if you want to really split hairs.)
Once upon a time I heard that "normal" is the diagonal of the sensor\film. So *for full frame it's 43mm* =) Multiply\divide by crop-factor to calculate it for bigger\smaller sensor\film formats. That easy.
The diagonal is important because it is not all about the angle of view but mainly you could consider the relation between foreground and background. A diagonal takes this into account, maybe. I am not an expert but this was my interpretation when I thought about it.
First of all, human vision is bi-focal (stereo-vision) with depth perception etc . Human field of view is defined not just by two eyeballs, but also human features as nose, eye sockets etc. So, our actual shape of fov is something like pilot helmet visor, for example, with very wide angle ( if not almost true 180, than at least 120 as mentioned, but it is hard to be exactly determined, since this varies from person to person. This could somehow relate to wide fish-eye lenses etc, but what we perceive as a sharp image with depth perception/focus etc, is finally related to something like 45 mm in leica format as noted, but than again, you can't really compare this directly. I think all this should be mentioned at the video.
Wow, thank again, that’s wonderful! (And an amazing video! 🤩🙌). Something that often feels a little overlooked in these conversations is compression and distortion. I definitely can’t reproduce the bokeh & separation of a subject in my eye, say that a 160mm lens can (or even a 85 1.2mm lens can), and at the same time, my binocular vision seems to distort the world less at close distances than a 15mm at its minimum focus distance can. Understanding how we see I believe is essential to understand to be a good cinematographer, just as much as understanding how the camera ‘sees’ and how these two are very different - and the creative endeavours this allows. (Think of how much work goes in to lighting a scene to create even exposure and separation for camera which renders its world in 2D, and all of that is mostly not needed when you see the same scene simply with your own eyes 🧡 🎬 (obviously there are the opposites too where the camera absolutely can see what we can’t), makes me marvel at the wondrousness of our ability to see!🧡).
You focus, pun intended, on the field of view: another thing to consider is the perspective or depth of field i.e. what is the relationship amongst objects in terms of their perceived distance one from another.
This to me is the only thing that's relevant when comparing to what the eye actually sees. Weather the distance is compressed or extended. The lens that matches this closest is closest to reality. Field of view is secondary to representing reality in a frame as seen by the human eye.
yeah this video completely misses the main point, that being perspective. That's really why these focal lengths are considered so close to our own eyes.
What I have found is that whenever I have a 40 or 50 mm equivalent lens in my camera and look at the viewfinder, what i see is equivalent to what I saw with my eyes. 40 a bit wide 50 a bit strict. I always thought the right answer to the human eye was something between these two focals. Thanks for the excellent video.
Great video, held me captive. Following the math interspersed with stunning cinematic clip examples. Using a cupola photo that represents the diagram of the human eye was a treat.
I once had a 75mm on a range finder style vertically up to my eye and everything about 1-3m away lined up perfectly with my other eye, leaving no overlap. So I guess it really depends on how you focus your eye.
Thank you for this. I was thinking for a Long Time that the rule that 50mm represents human eye is wrong and that we can shift between several focal lengths. Thanks for giving me the scientific data for my thoughts ❤
My preferred measurement and comparison of camera focal length vs the human eye is the size and distance objects appear in the foreground vs the background. As you know, wider lenses cause objects in the background to appear smaller and farther away compared to the object in the foreground, and vice versa with telephoto lenses. Using this definition, what focal length is most similar to the human eye? I believe the answer is about 42-50mm.
There's no focal length that is most similar to the eye. When we're scanning a wide scene, our eyes are effectively taking in a broader view, akin to a shorter focal length. This wider perspective allows us to perceive more of the surrounding environment, similar to how a wide-angle lens (much wider than 42mm) captures a broad field of view in photography. Conversely, when we're focusing intently on a specific object or detail, our eyes effectively "zoom in," narrowing our field of view to concentrate on that point of interest. This narrowed focus mimics the effect of a longer focal length (much longer than 50mm), isolating the subject and emphasizing its details, much like a telephoto lens in photography. The breadth of our visual experiences varies greatly depending on factors such as our surroundings, what we're focusing on, and our individual attentional focus. Therefore, it's not appropriate to generalize our visual perception to fit within a specific focal length range like 42-50mm.
Good video, but you talked of field/angle of view, and not perspective. Wide angle lenses and telephoto lenses distort perspective. The rate at which things look smaller as they get further away varies with focal length. The human brain judges how big or far things are using a fixed expectation of how the eye sees things. I want to know which camera lens most accurately mimics the human eye in that respect.
yeah this video completely misses the main point, that being the 40MM-50mm gives you the same perspective of human vision, as far as distance, compression of view goes.
I watched the whole video, and I couldn't really understand it. Isn't there a big difference between "field of view" and "perspective" ?? I thought around the 50mm mark was the perspective of the human eye, obviously not the FOV. You can take a picture of somebody face at 15mm and 50mm, having the exact same FOV (taking the shot closer with the 15mm, and moving further back with the 50mm). Both pictures will have the same field of view, but the perspective will be radically different. Maybe I'm missing something here??? I found a good quote from a photography forum about this: "A 25mm lens at 10ft will give you the same field of view as a 50mm at 20ft, but the perspective will be different. The 25mm will give you a much wider view of the background behind the subject, whereas the 50mm will tend to slightly compress the foreground and background. If you were to then change to a 100mm lens at 40ft, you would again have the same field of view, but the perspective would change, and the backgrounds would be even more compressed"
There's no such thing as the "perspective of the human eye." By moving further back with a 50mm lens, you don't achieve the same field of view (FOV) as with a 15mm lens. While you might capture the same objects, the shift in position inherently alters the composition. You can't change the FOV of the lens simply by moving. What you're overlooking is that the lens doesn't directly affect perspective; rather, it influences the cropping of what is seen through it. A lens serves as a window through which the camera perceives the world, and different focal lengths change the size of that window without altering the content seen inside. With a 15mm lens, you could achieve the same perspective and field of view as a 50mm lens shot from the same spot by simply performing a centered crop of the picture afterward. The primary noticeable difference would be the blurriness of the background.
The best assessment I saw. I like you described which focal length represents which aspect of our vision the best. It well corresponds with how we use a wide / 35 mm / 50 mm (or 42:) / portrait / tele in photography = how much of our focused or peripheral vision we use to perceive the image from details to environmental context. Well done.
This makes sense to me. Since the eyeball can't really change it's shape that much, the brain selectively takes in information from the area of the retina which is most appropriate for the situation. If you stood on a hill and looked out across the landscape without focusing on anything in particular, you are taking in a wide field of view which lacks detail. If you then catch the movement of a deer in that scene, your brain relies on the center portion of the retina to analyze the potential prey. So you "zoom" in on the deer, even though all you are doing is focusing the eye on the target and allowing the brain to take render a detailed image from all that information.
To have a same perspective as human eye lens needs to achieve 1x magnification. Magnification = focal length / exit pupil. Exit pupil is give or take equal to the sensor diagonal lens is made for... in case of full frame ( 36 x 24 mm ) diagonal is d = √( 24^2 + 36^2) = 43.2mm 1 = focal length / 43.2 -> focal length = 1 * 43.2 = 43.2mm Meaning in theory with full frame lens to achieve 1x magnification would need to have a focal length of 43.2mm. In reality exit pupils are larger, to limit vignetting... how much depends on a specific lens, more expensive the lens... less it vignettes because they made the exit pupil larger.
Also... this only talks about perspective not the actual field of view. Humans have huge field of view because the image we see is formed in our brains and it has very little to do what the retina actually sees at given point in time. We have two eyes our brain uses to construct 3D vision. That's why we have relatively wide field of view compared what 50mm or even 35mm lens has.
The focal length is the distance between the optical center of the lens and the image formed when the lens is focused on infinity. Normal Lens (also called a Standard Lens)-a lens with a focal length that is equal to the diagonal of the format. The diagonal of a 24x36mm film image is 43.267mm. The diagonal of an APS-C image is 28.3mm. The diagonal of a micro 4/3 image is 21.6mm.
I generally find the argument kinda weird to start with because a photo is nothing to a human until it is observed. How is the user going to observe an image? That matters a lot to how it, and the focal length used, is perceived. Imagine looking at a small print, 4x6 (10x15). On that size, a normal or telephoto shot looks more "real" to me. It is like having a tiny window to look through, where you only see a small FOV of the world through that window. At the same time, now imagine sitting in a huge cinema with a screen surrounding your vision. A telephoto image would look weird, while a wide angle image might look perfectly normal to me. The "normal" focal length should be one which would match the FOV of the final image. Obviously you can ignore that rule and do whatever you want, but i feel like if you want to match "a normal look", you should try to match the FOV of the image how it will be presented.
Yes exactly, this is my understanding as well. To take your example even further, imagine stretching the cinema screen all around you so that you are sitting inside a "cinema ball". Or to take a more normal example, imagine watching a scene in vr glasses. This is more similar to what we see with our eyes. Except in the real world you also have actual depth. Asking what focal length our eyes have in the way this video does becomes kind of strange. Not just because our eyes and brain are different to a camera. But mainly because we are watching a 360° world. In a similar way it would be strange to ask: What is a "normal" focal length of a 360-camera. You could (I think) theoretically (not practically) use any focal length you want for the lenses in a 360-camera and the resulting stitched image would have the same "depth compression" anyway. Simply because it is a 360° image viewed from "inside". But maybe I'm just complicating things. The main thing is, exactly as you've said, that there is no objective "normal" focal length. It depends on the size of the image and the viewing distance.
it's always the diagonal of the sensor/film which defines the so called Standard.. and it's always 43,3 in FF or 54,8 on a 44x33 Medium format... 21,63 on m43 sensors... and it always equals the same 43~ mm but it has nothing to do with the Human eye... we have two eyes... and there is a 3rd Dimension
Problem is: sensor diameter isn't always the thing you can measure across all aspect ratios. For example, the sensor of my Blackmagic pocket cinema camera 6k is wider, making it a 23.sth mm diameter. BUT the crop factor is around 1.558, and you won't get the 43mm with those measurements.
42 is the logical answer, of course :) The edges beyond that lack detail. But we should take into account that our eyes are moving constantly. When we look at a landscape, we are stitching a panorama out of several "normal" shots.
An additional nuance is that we have strong brain post-processing. For example, when we look at a small object in the distance, our brain essentially crops the frame and the image from a 200+mm lens can appear very natural. Also, our eyes can move quickly, and our brain can stitch shifted images into one. So landscapes shots with an ultra-wide lens can also appear natural
I've always wondered about this! I look in my 35mm and it feels wider than what I was looking at. My 50mm feels 'cropped' when I bring the camera to my eye. This explains a lot! It's a shame the 42mm (ish) aren't more common. I know they're (40mm) used in cinema, but definitely not common in consumer lenses. Thank you for discussing this!
My 1970's era Olympus 35RC film rangefinder has a 42mm lens which I love, and Panasonic makes a great 20mm lens for Micro Four Thirds digital whose field of view is equivalent to 40mm on full frame.
Great explanation of the physics here. Well done sir. Recently I travelled to our nations's capital and went crazy shooting with a standard zoom at specific focal lengths that can be bought as primes; 28, 35, 40 and 50mm. The idea was to document, capture interesting images and to understand my perception of a scene vs capture. Of course there are artistic/compositional and other reasons to choose a particular focal length, but in perception/capture terms when I reviewed the images, for me 40mm got it best.
The binocular "frame" is where the fields of both eyes intersect, so it should be equivalent to a 12x24 frame (stretched vertically), rather than 24x12. Our eyes are spaced out horizontally, not vertically, so the binocular area should be almost as "tall" as the entire field of view, but relatively narrow. Also, "retina", not "rentina". Otherwise, interesting way to think of an eye as sort of an "all-in-one" lens because of retina resolution increasing towards the center.
In trying to represent medical pathology as the eye sees it for the last 7 years, I have realised; somehow, perspective distortion changes at different working distances, requiring different focal lengths. Therefore, 35mm matches within 50cm, 50mm matches between 50cm and around 3-5m depending on the pathology, 85mm matches between 5m and around 100m and above those distances, a larger focal length is needed. Varying too far out of this, and the subject is either excessively distorted or flat. Am I hallucinating?
Finally someone went and did their research on this! I think it's simultaneously coincidental and intentional. Cameras are made by humans for humans to use to make things for other humans to enjoy. It just goes to show you how brilliant and intuitive the early engineers and photographers were even before the advanced technology of today.
What people dont get is that human vision bears no relationship whatsoever to cameras and video; there is no image from the human eye. No surprise as the image quality from the human eye is terrible and barely useable but, that isnt its function. Our greatest resolution is in the centre where we have our greatest concentration and that is the key to understanding. Human vision is more like an electron microscope than a camera; its a scanning system. The brain builds an image from fragments of monochrome images. I find my own image size is anamorphic (wonder why they chose that for film he he) and I take panoramic street photos. That we see in B&W was discovered by Edwin Land (of Polaroid) quite late when he discovered he could generate colour by spinning a B&W target. The brain works out the colours by comparing contrast between images from different wavelengths. Everything we think we see is completly generated in the brain. Because we scan the scene, taking longer over points of interest, the eye has infinite depth of field; you dont see anything out of focus. You even see things that arent there as the eye uses RI (real intelligence he he) to fill in gaps its not sure about (e.g. covering the blind spot on the retina). What we can focus on in eye tests is all about resolving resolution; for you to focus on something you have to be able to resolve the detail so the brain can reconstruct it. Also the eye only has about 10stops of dynamic range (sorry photographers who like to lift shadows using massive dynamic range sensors). To see in a different range we have to let the eye accommodate for several minutes and we can accommodate from blinding to almost dark given enough time. Despite the fact we have known all this for decades it amazes me that we still think of everything we thought in the days of Barnack - winks ;-)
This actually matches my recent observation that the 3x camera of the iPhone (equivalent to 72mm) very closely resembles the natural perspective of the eye when looking at a combination of near and far objects. Like looking out through a window from a bit of distance, with the window frame in view as well as the outside world. Cool and very informative video.
A big thing to remember when talking about vision is how your brain perceives it. While the actual *Physical* focal length of the human eye is around 25mm, your brain take the stimulation from the cones and rods and maps it out and distorts it such that it looks to be closer to 50mm. Your vision is something your brain does a lot of heavy lifting for, like how it removes the hole in your vision where your optic nerve starts, or removing your nose when looking forward, or filling in the blanks of your periphery when you're not looking at something directly. A fun (and funny way) I found to really test out the weird things that happens to your vision when you push it to the extremes is this: Have someone that you're close to (spouse, partner, sibling, or close friend.) Close one of your eyes and, with your open eye, put your face right up against theirs with your eye centered on the very top part of where their nose starts. If you keep your center vision focused there but then try to focus on your peripheral vision, you'll notice that you can still actually see both their eyes and even past their head, but it almost looks like an extreme fish-eye effect. Your eye, even less than a half-inch away, can not only see someone's eyes and cheekbones but even past them as well. When you see do this you actually get to somewhat really perceive how wide your FOV truly is (more akin to the actual 25mm distance) but in normal day-to-day activities and with both eyes your brain reformats your vision seamlessly to look like that 49mm-73mm range. The question isn't "what is the focal length of the human eye?", its "What's the ***perceived*** focal length of human vision?"
Thanks for breaking down this issue in such an easily digestible way! I always get annoyed when people claim that this or that focal length is how the human eye sees - when we obviously have a really, really wide field of view, but can also focus our attention to a part of that field of view. One thing that I was missing from the discussion (maybe something for a follow up video?) is the fact that perception of focal length changes with the size of the image we're seeing, or the distance respectively. Anecdotal evidence: when I first put a 35mm lens on my A7C and looked at the image through the abisally small EVF, it felt really unnatural and weirdly wide angle to me. Not so with other cameras. And when I put a 5.5" monitor on my camera, all of a sudden 35mm feels entirely different. When I view 35mm footage on my computer screen, it feels different yet again. And if I had the ability to stream an image directly into my brain, it would feel different yet again.
Leica actually made a 40mm summicron C for the CL cameras. It’s M mount and quite affordable. Not may people use it because no M camera has the 40mm viewfinder lines.
My first 35mm camera was an Olympus 35 SP with a 42mm lens. I came to realize after many other cameras, that I liked to 42mm perspective on full frame. Unfortunately, not too many prime lenses in the 40-45mm range for full frame digital cameras.
My favorite Nikon zoom lens was 43-86. Of the fixed lens rangefinder cameras I have, only the Olympus SP has a 42mm lens. Great video, love your explanations about the eye in relation to focal lengths!
This is probably the best video on the topic of 'natural focal length' I have seen. Great job! For me the most natural representation is between 70-90mm. 40-60mm with still somewhat useful peripheral vision. Wider focal length is just a danger/movement detector with no meaningful resolution.
It's 43.27mm which is the diagonal of a full frame sensor, as the eye is a sphere it roughly approximates the relationship between flange distance and focal length of the eye ball
I did an experiment with a 20 to 70mm zoom lens where i carefully observed a street scene without focusing on any particular part. So just look straight ahead and noticing what was clearly in focus without moving my eyes around. I thought i was going to end up with 50mm as that is what i had been told for years was the normal vision. But for me the closest was somewhere in the range of 30 to 35mm. I still find 35mm the most normal looking focal length...but i also wonder if thats just years of looking at newspaper photographs growing up
For *Close to Far* (how far things are from each other and from the viewer), the 42mm is indeed closer to how human eye perceives distances. But not in terms of "how much of the scene" we see (field of view). If you hold your hand next to your head, your peripheral vision still captures it (almost fisheye field of view but not sharp). I would say the human eye is "an almost fisheye lens corrected like a 42mm for distance perception and distortion".
this explains a lot. ive always considered the argument of eyes to focal length is corner to corner and it felt about the same as an eq 18mm lens i used, hearing people say your vision is about 50mm really started to confuse me! very educational video
actually this video completely misses the main point, that being the 50mm gives you the same perspective of human vision, as far as distance, compression of view goes, it doesn't give us the same field of view, but gives us the same perspective, where as 18mm flattens out the image and distorts it in a way our eyes do not.
One rule of thumb is that a “normal” lens would have a focal length equal to the diagonal of the sensor. In the case of full frame, that is about 43mm. If you use a camera with a different aspect ration, such as 4:3 medium format, it is not so obvious what the focal length equivalents should be. Using the relative diagonals is a compromise, and sometimes you may want equivalent width or equivalent height. My first 35mm camera had a fixed 45mm lens, so that looked normal to me out of habit and experience.
When I look through an old film SLR where the viewfinder is designed to appear at 100% magnification, the image I get with a 50mm lens focused toward infinity matches/lines up with the image that I see with the other eye. 50mm, give or take, seems to produce the same compression and angular perspective as human vision.
Nice. I’m a Leica M user, and always appreciate great optical quality. And… my latest purchase, the Hasselblad 55V is 43mm in 35mm measurement… Perfect 😅
That was very interesting! Works in photography too. And it explains why some photographers prefer 35 mm as their "go-to" focal length, some 40 mm, or 45 mm, or 50 mm (or even 55 mm). I'm comfortable with 35 or 50 mm, more leaning to 50 mm (for me it's more about details).
Interesting! Thanks! Let me just ask, because I don't get it: How is the grey "full frame 36x24mm" frame in the diagrams taller than the blue "full retina 40x27mm"?
For me, there's a combination between sensor/emulsion size vs lens. And the answer is quite simple and not subjective. In a normal lens, when you look through the lens while keeping both eyes open, you should see no change in perspective, meaning the size relation between near and far objects. As a guide, you should be able to walk with no problem using the normal lens while viewing through the viewfinder, and then the lens, and you should feel no change at all between both eyes. The confusion starts by the fact that people use the same language for different things ("35mm format", or "35mm film") Full frame is one thing while Super 35 or cinema 35mm format is a different size. Hence, when looking through a stills photo camera the "normal lens" is around 80mm; in 35mm cinema film cameras is around 50mm. So it's not a "democratic" thing, but a real fact. Human vision is quite wider than what you can see through the lens, but as the purpose for this is to capture images as we see them, the whole idea is to be able to capture the relation between the things in front of the camera as we see them in relation to each other, in disregard of the full wide view that our brains render.
What about lens compression? What focal length and at what distance is closest to the human eye? when using 15-22 or even 35 I don't see the same compression
Appreciate this. I’m relatively new to photo and found 35mm to be a relief but not quite there, and on the high end I don’t have the budget to figure out why my 135mm isn’t narrow enough, but 200mm photos online don’t do it for me either. I’ll have a better chance at finding my ideal lenses now.
Is there somewhere we can see a list of the films used during your video? Looked like some interesting frames! Love the 40-45mm lenses, Canon, Leica, Minolta and Pentax make some stellar examples! Thanks
Always tricky to determine focal length when trying to render out a human view in 3D, so perspective looks correct, especially useful when trying to figure out optical illusions
Most of this is missing a very important point. When we have the correct field of view (the AREA in view) the objects are not the correct size as seen by the eye. The correct focal length for size to match the human eye is 58mm. Just put a camera with a 50mm lens on it up to your eye and look through the viewfinder, at the same time open the other eye and the differnce in size can be seen,50mm too small, 58mm correct size.
I like to speak of the eye-brain-system which has to be imitated by the photographer or cinematographer. The unfocused view is very wide, the focused view on details is more tele. This video is a great visualization and explanation of that, and now I see my thoughts confirmed. Thanks! EDIT: And the video stands out because you say that we shoudn't be religious with the 43.0000 mm focal length!
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Finally! A reasonable, educated and intelligent answer to an often extremely foolishly answered question
I think this answer is silly. And there is no such thing as the focal length of the human eye, especially not in connection to cameras. This completely disregards the image size we are looking at and the distance of it. And that human vision is very different anyways.
After shooting with 35mm, 50mm and 85mm lenses in my pursuit of finding my perfect focal length for my photography, I had some interesting findings. =50mm seems formal and more strict. And then I found 40mm. 40mm had a true, genuine, real, even a humble feel. I realized that there was something special about 40mm, and seeing this video it makes sense to me why!
an this is why I just love my Ricoh GR3X. I just dont want another camera or focal length
U doing to much
Full frame or apsc?
It's funny I have lenses ranging from 28 to 40 to 50 to 70 to 85 and 200mm. When I hold them up to my eye on the camera and then look at the object,the lens that matches up best with what I'm seeing with the naked eye is 70mm. 40mm is much wider and further away.
@@jabezhane70mm is my normal - feels correct to what I see.👍🏽
Out of the dozens of sources I've seen cover this topic this is by far the best. The effect of mental focus on your subject and it's effect on apparent subject size is typically ignored completely when covering this topic. I especially liked how you discussed there being one focal length that's closer to the human eye when you are broadly taking in a scene versus a scene where you are mentally focused on a subject, that has an immense impact on the apparent equivalent lens focal length.
When I'm not focusing on anything in particular my field of vision is something close to around 18mm but the size of objects within that field of vision appear closer to how a lens around 60mm would make them appear. This simultaneous dual focal length is just not something a camera with a single lens and no brain can recreate so it makes sense to pick a focal range that is a good balance of fov and magnification and call lenses that fall within that range as "normal". Personal preference of fov vs magnification is going to affect what people think is more normal for them individually. I tend to lean toward fov as being more important when thinking about making a scene look more normal but I don't necessarily want subjects to appear too small in the frame so I like focal lengths in the 28-35mm range for representing normal, 50mm cuts off way to much of my peripheral vision to appear normal, even though subject size is closer to normal for me. If I were to average my fov and magnification preference I get 40mm as my average normal which is very close to the original Leica you mentioned. Konica made an excellent Hexanon 40mm f1.8 lens but I'm not sure if there are others.
Pentax would agree with you. They created the FA 43mm F1.9 limited back in the 1990's
It turns out the focal length of 43mm was a byproduct of lens design constraints Pentax imposed for the Three Amigos rather than to fit this fact that 43mm on a 135 format sensor corresponds to 1 radian. It's why the other two lenses have 77mm and 31mm as their focal lengths.
Once again. Is the answer to all questions 42 😂👀👀
❤
Ha ha....after millions of years of waiting....the answer is: 42
Yes! And.. don’t panic.
The diagonal of my towel. Always ready.
Thanks for the fish!
This makes so much more sense to me. I've always felt like 28mm or wider is pretty decent at capturing an entire scene like a landscape sort of as I see it. And 50mm is closer to focusing on a detail or a face. Just saying 'this is the focal length' always seemed very silly to me. Thanks for the very detailed video, very educational.
You’re welcome!
This is why my every day lens on a full frame camera is a 40mm and a 24mm on APS-C. When I put the camera up to my eye, what I see in the frame is pretty close to my generalized perception where I'm just taking in the world writ large without focusing or paying attention to any one thing. If I'm focusing or paying attention to something, closer to 70mm is about right, and 150+ feels like tunnel vision.
I tried this with a Canon 5D and a 70mm-200mm zoom lens... when at 70mm, if you put the camera up to your eye and looked through the viewfinder, everything was the exact same size as when you looked at it with your naked eye, even if the field-of-view is significantly narrower. If you could have a lens with the focal-length of a 70mm lens, but the peripheral view of a fish-eye lens, then you'd have a lens that gives us the same view as a human eye.
I think what's happening at the 42mm length is that it's the balance point between the focal length of the human eye, and the wider peripheral view. It's a nice medium that satisfies us just enough on both those factors. If you JUST want peripheral view, then Kubrick's favourite lens of 14mm is probably the way to go to capture that feeling without worrying about size of objects, depth-of-field, etc, being accurate to the human eye. It just gives that "taking it all in" feeling of using your whole field of view instead of focusing on specific objects.
Nice video! Just one clarification: Oskar Barnack never designed lenses. It was Max Berek the genius behind the Leica glass. The 42mm for the UR-Leica was a microscope lens (Summar) that was chosen because it was already available for Barnack's proof of concept. However, they needed a much better lens for the enlargements that were needed to compete with the quality of the prints that were on the market then. The 50mm was easier to design and there were already many examples around to get inspiration from.
Max Berek is credited in the video.
I always argue we should not compare photography and human vision in terms of field of view / view angles, but we should compared in terms of perspective, i.e. how we perceive the distance / spacial relationships between the subject and its background surrounding it. That way what we called "normal" lens projects the prospective closest to how we understand the depth relationship in real world is making more sense to me.
I make shows in large spaces round the world we often shoot reference images for the team who arnt on the early trips. The perspective relationship of buildings we might project on is extremely important for designing any sets etc. in large spaces with lots of depth the apparent size of objects always feels most natural to me when shooting near 50mm this really became clear when we were projecting on the Washington monument as there is so much space. When we used 48mm in camera and software our visualisations matched the real world relationships of scale. I’ve never really understood the focus on fov as our perception is so based on building images from many samples and who can really feel the edge of their vision without really focusing on it. How big things are in relationship to each other is how we really feel our place in the world.
yeah I was waiting for this video to get to the perspective part and it just didn't, completely missed a major part of why we consider these normal human vision lenses.
Thank you, haha I threw myself into writing a comment about perspective and then found you comment. Perspective, a natural compression of objects relationship to each other in a 3D space is way more important than field of view for a natural look.
This is for me the most important point, mostly because it has a huge impact on photography and why photographs with big depth differences in the scene always look worse than what you see in real life. YOu can either capture only a very small part of it or the entire scene but with massively skewed spatial relationships.
A good paper about this can be found googling "Natural Perspective", which is mostly aimed at rendering but gives some great examples by comparing paintings and photographs of the same scene and how different they look.
I always thought that the "normal" focal lenght was something around 43mm because the diagonal of a full frame sensor is 43.27mm. But this video explains there is more about it. Very interesting, thank You!!
This is actually correct.
The diagonal of any sensor size will produce a normal* field of view.
In 1914, the Multi-Speed Company in the United States had a 35mm camera called the Simplex Multi-Exposure which carried a Bausch & Lomb 50 mm f/3.5 Tessar lens.
While in Germany Oskar, reportedly had no clue that such a small-format camera was being advertised in the United States (the Tourist Multiple of Herbert & Huesgen premiered in 1914 to a U.S. population as well), 10 or 11 years before his accomplishments with Leica.
Therefore, I don't know if back then, could the 50mm lens be a starting point or was the 42mm lens a debatable counter point?
Excellent content & insight that you expressed here. I enjoyed it.
In author Douglas Adams’s popular 1979 science-fiction novel The Hitchhiker’s Guide to the Galaxy, toward the end of the book, the supercomputer Deep Thought reveals that the answer to the “Great Question” of “Life, the Universe and Everything” is “forty-two.”
One of the best videos I've seen lately. Awesome work. I'm a doctor and I love photography. It was a double treat for me.!
Since the length of the human eye along its optical axis, from the front of the cornea to the retina is approx 24 mm, then I would suggest the focal length is 24mm when relaxed (i.e. focused on infinity), changing by distortion of the crystalline lens to a shorter focal length when focused on a closer object!
Do this experiment;
Take a zoom lens on your camera and focus on an object in your room. Lets say a TV from 8 feet away. Put the camera away from your eyes and then put the camera back up to your eyes and continue to adjust the zoom until the magnification matches what you are seeing in the real world. In full frame terms it will probably be somewhere around 65mm-70mm(Lets say it's 67mm). The caveat is that the full frame obviously show a extreme cropped version of what you see in the real world since it's only full frame. If you have the 67mm on a medium format if shows more the the scene and then large format again even more at the same focal length.
This is one of the reasons why I hate wider lens for most landscape shots. A 20mm lens on full frame has too much distortion and it doesn't match what I'm actually seeing and even 35mm is too tiny...the only thing the wider lens are doing is letting me see more of the scene at a cost. This is the major advantage of the bigger formats. Ansel Adams for example shot a lot of Hasselblad 6x6 with a 80mm lens but it allows you to see pretty wide at 6x6 compared to full frame. It's also one of the reasons I love Nolan IMAX movies. He's shooting a lot with 80mm lens and the look is distinct from everything else.
Hooray...this person gets it.
I've been waiting years for this video. Thank you.
You're very welcome!
Leica actually made a 40mm lens for the Leica CL in the early 1970’s. Rollei and Ricoh, among others, made 40mm lenses for their film point & shoot cameras.
Years ago, when I worked in a camera shop, we used to reference 42-43mm as an "eyeball" normal, meaning the most used "normal" lenses (35mm and 50mm) were somewhere around 8mm wider or 7mm longer than that benchmark. I am currently shooting with a 2/50mm Zeiss Biogon on my rangefinder, which feels that it is really 47mm-48mm - a little wide from what I expected when compared to an old 50mm Dual Range Summicron. In use, I feel a little less constrained than I did with the 50mm. Great video - thanks!
Surveying the landscape of vintage photographic (not cinema) film cameras, I noticed an oddity. 50mm was considered the standard normal lens among 35mm film (i.e. small format, 135 Format) rangefinders and SLRs with interchangeable lenses. As soon as you moved outside of that category, and you start considering medium format cameras, and even fixed-lens small format cameras, the 50mm focal length fixation largely dissipates. A lot of them had 35mm or 40mm equivalent lenses. I mean for example, consider how many Olympus Trip cameras were produced with 40mm lenses!
Personally, one of my most-used prime lenses is 28mm on my APS-C camera bodies, which, taking account of the crop factor, works out to… hmm… 42mm! (OK, 42.8mm if you want to really split hairs.)
I am using a Viltrox 27mm on my Fuji so 40.5mm on FF. It seems pretty accurate and I love using it.
Once upon a time I heard that "normal" is the diagonal of the sensor\film. So *for full frame it's 43mm* =) Multiply\divide by crop-factor to calculate it for bigger\smaller sensor\film formats. That easy.
The diagonal is important because it is not all about the angle of view but mainly you could consider the relation between foreground and background. A diagonal takes this into account, maybe. I am not an expert but this was my interpretation when I thought about it.
First of all, human vision is bi-focal (stereo-vision) with depth perception etc . Human field of view is defined not just by two eyeballs, but also human features as nose, eye sockets etc. So, our actual shape of fov is something like pilot helmet visor, for example, with very wide angle ( if not almost true 180, than at least 120 as mentioned, but it is hard to be exactly determined, since this varies from person to person. This could somehow relate to wide fish-eye lenses etc, but what we perceive as a sharp image with depth perception/focus etc, is finally related to something like 45 mm in leica format as noted, but than again, you can't really compare this directly.
I think all this should be mentioned at the video.
Wow, thank again, that’s wonderful! (And an amazing video! 🤩🙌).
Something that often feels a little overlooked in these conversations is compression and distortion.
I definitely can’t reproduce the bokeh & separation of a subject in my eye, say that a 160mm lens can (or even a 85 1.2mm lens can), and at the same time, my binocular vision seems to distort the world less at close distances than a 15mm at its minimum focus distance can.
Understanding how we see I believe is essential to understand to be a good cinematographer, just as much as understanding how the camera ‘sees’ and how these two are very different - and the creative endeavours this allows.
(Think of how much work goes in to lighting a scene to create even exposure and separation for camera which renders its world in 2D, and all of that is mostly not needed when you see the same scene simply with your own eyes 🧡 🎬 (obviously there are the opposites too where the camera absolutely can see what we can’t), makes me marvel at the wondrousness of our ability to see!🧡).
You focus, pun intended, on the field of view: another thing to consider is the perspective or depth of field i.e. what is the relationship amongst objects in terms of their perceived distance one from another.
This to me is the only thing that's relevant when comparing to what the eye actually sees. Weather the distance is compressed or extended. The lens that matches this closest is closest to reality. Field of view is secondary to representing reality in a frame as seen by the human eye.
Look at my definition in my comment above. That is what you are looking for.
yeah this video completely misses the main point, that being perspective. That's really why these focal lengths are considered so close to our own eyes.
What I have found is that whenever I have a 40 or 50 mm equivalent lens in my camera and look at the viewfinder, what i see is equivalent to what I saw with my eyes. 40 a bit wide 50 a bit strict. I always thought the right answer to the human eye was something between these two focals. Thanks for the excellent video.
Great video, held me captive. Following the math interspersed with stunning cinematic clip examples. Using a cupola photo that represents the diagram of the human eye was a treat.
Thank you!
Leica has recently released the Leica Q3 43 compact camera with a fixed lens with an angle of view of 43 degrees on full frame.
When Kai W was at DigitalRev TV he said the human eye sees at 43mm and only Pentax makes that lens.
As this video suggests, there is nuance. Anyone who denies there is nuance in the field of science would be a fool.
I once had a 75mm on a range finder style vertically up to my eye and everything about 1-3m away lined up perfectly with my other eye, leaving no overlap. So I guess it really depends on how you focus your eye.
I love the way you calculated the different values. Good work
Thank you for this. I was thinking for a Long Time that the rule that 50mm represents human eye is wrong and that we can shift between several focal lengths. Thanks for giving me the scientific data for my thoughts ❤
My preferred measurement and comparison of camera focal length vs the human eye is the size and distance objects appear in the foreground vs the background. As you know, wider lenses cause objects in the background to appear smaller and farther away compared to the object in the foreground, and vice versa with telephoto lenses.
Using this definition, what focal length is most similar to the human eye? I believe the answer is about 42-50mm.
There's no focal length that is most similar to the eye. When we're scanning a wide scene, our eyes are effectively taking in a broader view, akin to a shorter focal length. This wider perspective allows us to perceive more of the surrounding environment, similar to how a wide-angle lens (much wider than 42mm) captures a broad field of view in photography.
Conversely, when we're focusing intently on a specific object or detail, our eyes effectively "zoom in," narrowing our field of view to concentrate on that point of interest. This narrowed focus mimics the effect of a longer focal length (much longer than 50mm), isolating the subject and emphasizing its details, much like a telephoto lens in photography.
The breadth of our visual experiences varies greatly depending on factors such as our surroundings, what we're focusing on, and our individual attentional focus. Therefore, it's not appropriate to generalize our visual perception to fit within a specific focal length range like 42-50mm.
Good video, but you talked of field/angle of view, and not perspective. Wide angle lenses and telephoto lenses distort perspective. The rate at which things look smaller as they get further away varies with focal length. The human brain judges how big or far things are using a fixed expectation of how the eye sees things. I want to know which camera lens most accurately mimics the human eye in that respect.
yeah this video completely misses the main point, that being the 40MM-50mm gives you the same perspective of human vision, as far as distance, compression of view goes.
I watched the whole video, and I couldn't really understand it. Isn't there a big difference between "field of view" and "perspective" ?? I thought around the 50mm mark was the perspective of the human eye, obviously not the FOV.
You can take a picture of somebody face at 15mm and 50mm, having the exact same FOV (taking the shot closer with the 15mm, and moving further back with the 50mm). Both pictures will have the same field of view, but the perspective will be radically different.
Maybe I'm missing something here???
I found a good quote from a photography forum about this:
"A 25mm lens at 10ft will give you the same field of view as a 50mm at 20ft, but the perspective will be different. The 25mm will give you a much wider view of the background behind the subject, whereas the 50mm will tend to slightly compress the foreground and background. If you were to then change to a 100mm lens at 40ft, you would again have the same field of view, but the perspective would change, and the backgrounds would be even more compressed"
There's no such thing as the "perspective of the human eye." By moving further back with a 50mm lens, you don't achieve the same field of view (FOV) as with a 15mm lens. While you might capture the same objects, the shift in position inherently alters the composition. You can't change the FOV of the lens simply by moving. What you're overlooking is that the lens doesn't directly affect perspective; rather, it influences the cropping of what is seen through it. A lens serves as a window through which the camera perceives the world, and different focal lengths change the size of that window without altering the content seen inside. With a 15mm lens, you could achieve the same perspective and field of view as a 50mm lens shot from the same spot by simply performing a centered crop of the picture afterward. The primary noticeable difference would be the blurriness of the background.
It depends on what format camera you use. With 35mm it is different than 6x6 etc.
The best assessment I saw.
I like you described which focal length represents which aspect of our vision the best.
It well corresponds with how we use a wide / 35 mm / 50 mm (or 42:) / portrait / tele in photography = how much of our focused or peripheral vision we use to perceive the image from details to environmental context.
Well done.
This makes sense to me. Since the eyeball can't really change it's shape that much, the brain selectively takes in information from the area of the retina which is most appropriate for the situation. If you stood on a hill and looked out across the landscape without focusing on anything in particular, you are taking in a wide field of view which lacks detail. If you then catch the movement of a deer in that scene, your brain relies on the center portion of the retina to analyze the potential prey. So you "zoom" in on the deer, even though all you are doing is focusing the eye on the target and allowing the brain to take render a detailed image from all that information.
To have a same perspective as human eye lens needs to achieve 1x magnification. Magnification = focal length / exit pupil.
Exit pupil is give or take equal to the sensor diagonal lens is made for... in case of full frame ( 36 x 24 mm ) diagonal is d = √( 24^2 + 36^2) = 43.2mm
1 = focal length / 43.2 -> focal length = 1 * 43.2 = 43.2mm
Meaning in theory with full frame lens to achieve 1x magnification would need to have a focal length of 43.2mm.
In reality exit pupils are larger, to limit vignetting... how much depends on a specific lens, more expensive the lens... less it vignettes because they made the exit pupil larger.
Also... this only talks about perspective not the actual field of view. Humans have huge field of view because the image we see is formed in our brains and it has very little to do what the retina actually sees at given point in time. We have two eyes our brain uses to construct 3D vision. That's why we have relatively wide field of view compared what 50mm or even 35mm lens has.
The focal length is the distance between the optical center of the lens and the image formed when the lens is focused on infinity.
Normal Lens (also called a Standard Lens)-a lens with a focal length that is equal to the diagonal of the format.
The diagonal of a 24x36mm film image is 43.267mm.
The diagonal of an APS-C image is 28.3mm.
The diagonal of a micro 4/3 image is 21.6mm.
I generally find the argument kinda weird to start with because a photo is nothing to a human until it is observed. How is the user going to observe an image? That matters a lot to how it, and the focal length used, is perceived.
Imagine looking at a small print, 4x6 (10x15). On that size, a normal or telephoto shot looks more "real" to me. It is like having a tiny window to look through, where you only see a small FOV of the world through that window. At the same time, now imagine sitting in a huge cinema with a screen surrounding your vision. A telephoto image would look weird, while a wide angle image might look perfectly normal to me.
The "normal" focal length should be one which would match the FOV of the final image. Obviously you can ignore that rule and do whatever you want, but i feel like if you want to match "a normal look", you should try to match the FOV of the image how it will be presented.
I agree. Natural focal length = picture distance / picture width x sensor width. I explain it in a comment.
Yes exactly, this is my understanding as well. To take your example even further, imagine stretching the cinema screen all around you so that you are sitting inside a "cinema ball". Or to take a more normal example, imagine watching a scene in vr glasses.
This is more similar to what we see with our eyes. Except in the real world you also have actual depth.
Asking what focal length our eyes have in the way this video does becomes kind of strange. Not just because our eyes and brain are different to a camera. But mainly because we are watching a 360° world.
In a similar way it would be strange to ask: What is a "normal" focal length of a 360-camera. You could (I think) theoretically (not practically) use any focal length you want for the lenses in a 360-camera and the resulting stitched image would have the same "depth compression" anyway. Simply because it is a 360° image viewed from "inside".
But maybe I'm just complicating things. The main thing is, exactly as you've said, that there is no objective "normal" focal length. It depends on the size of the image and the viewing distance.
it's always the diagonal of the sensor/film which defines the so called Standard.. and it's always 43,3 in FF
or 54,8 on a 44x33 Medium format...
21,63 on m43 sensors...
and it always equals the same 43~ mm
but it has nothing to do with the Human eye...
we have two eyes... and there is a 3rd Dimension
Problem is: sensor diameter isn't always the thing you can measure across all aspect ratios. For example, the sensor of my Blackmagic pocket cinema camera 6k is wider, making it a 23.sth mm diameter. BUT the crop factor is around 1.558, and you won't get the 43mm with those measurements.
@@SolidBlueBlocks
now i took a short look on it... the diameter is 26,5mm
and if i multiply it with 1.6 (1.558)
yes... again the Magic number 🤭
42 is the logical answer, of course :) The edges beyond that lack detail. But we should take into account that our eyes are moving constantly. When we look at a landscape, we are stitching a panorama out of several "normal" shots.
An additional nuance is that we have strong brain post-processing. For example, when we look at a small object in the distance, our brain essentially crops the frame and the image from a 200+mm lens can appear very natural. Also, our eyes can move quickly, and our brain can stitch shifted images into one. So landscapes shots with an ultra-wide lens can also appear natural
Yep. That's always going on. Our field of view is actually much much wider than 42mm. Probably more like 16mm
Really good and really informative. Thank you. FWIW the Hasselblad XCD 55V translates to a 35mm format 43mm lens.
And Fujifilm GF 55mm f1.7 as well👌🏽
I've always wondered about this! I look in my 35mm and it feels wider than what I was looking at. My 50mm feels 'cropped' when I bring the camera to my eye. This explains a lot! It's a shame the 42mm (ish) aren't more common. I know they're (40mm) used in cinema, but definitely not common in consumer lenses. Thank you for discussing this!
My 1970's era Olympus 35RC film rangefinder has a 42mm lens which I love, and Panasonic makes a great 20mm lens for Micro Four Thirds digital whose field of view is equivalent to 40mm on full frame.
Panasonic Leica DG Nocticoron 42.5mm F/1.2 fits perfectly. A fabulous portrait lens for MFT
Great explanation of the physics here. Well done sir. Recently I travelled to our nations's capital and went crazy shooting with a standard zoom at specific focal lengths that can be bought as primes; 28, 35, 40 and 50mm. The idea was to document, capture interesting images and to understand my perception of a scene vs capture. Of course there are artistic/compositional and other reasons to choose a particular focal length, but in perception/capture terms when I reviewed the images, for me 40mm got it best.
The binocular "frame" is where the fields of both eyes intersect, so it should be equivalent to a 12x24 frame (stretched vertically), rather than 24x12. Our eyes are spaced out horizontally, not vertically, so the binocular area should be almost as "tall" as the entire field of view, but relatively narrow. Also, "retina", not "rentina".
Otherwise, interesting way to think of an eye as sort of an "all-in-one" lens because of retina resolution increasing towards the center.
In trying to represent medical pathology as the eye sees it for the last 7 years, I have realised; somehow, perspective distortion changes at different working distances, requiring different focal lengths. Therefore, 35mm matches within 50cm, 50mm matches between 50cm and around 3-5m depending on the pathology, 85mm matches between 5m and around 100m and above those distances, a larger focal length is needed. Varying too far out of this, and the subject is either excessively distorted or flat. Am I hallucinating?
Excellent video for everyone specially for photographers.
Finally someone went and did their research on this! I think it's simultaneously coincidental and intentional. Cameras are made by humans for humans to use to make things for other humans to enjoy. It just goes to show you how brilliant and intuitive the early engineers and photographers were even before the advanced technology of today.
What people dont get is that human vision bears no relationship whatsoever to cameras and video; there is no image from the human eye. No surprise as the image quality from the human eye is terrible and barely useable but, that isnt its function. Our greatest resolution is in the centre where we have our greatest concentration and that is the key to understanding. Human vision is more like an electron microscope than a camera; its a scanning system. The brain builds an image from fragments of monochrome images. I find my own image size is anamorphic (wonder why they chose that for film he he) and I take panoramic street photos. That we see in B&W was discovered by Edwin Land (of Polaroid) quite late when he discovered he could generate colour by spinning a B&W target. The brain works out the colours by comparing contrast between images from different wavelengths. Everything we think we see is completly generated in the brain. Because we scan the scene, taking longer over points of interest, the eye has infinite depth of field; you dont see anything out of focus. You even see things that arent there as the eye uses RI (real intelligence he he) to fill in gaps its not sure about (e.g. covering the blind spot on the retina). What we can focus on in eye tests is all about resolving resolution; for you to focus on something you have to be able to resolve the detail so the brain can reconstruct it. Also the eye only has about 10stops of dynamic range (sorry photographers who like to lift shadows using massive dynamic range sensors). To see in a different range we have to let the eye accommodate for several minutes and we can accommodate from blinding to almost dark given enough time. Despite the fact we have known all this for decades it amazes me that we still think of everything we thought in the days of Barnack - winks ;-)
This actually matches my recent observation that the 3x camera of the iPhone (equivalent to 72mm) very closely resembles the natural perspective of the eye when looking at a combination of near and far objects. Like looking out through a window from a bit of distance, with the window frame in view as well as the outside world.
Cool and very informative video.
What a great video! Thanks!
A big thing to remember when talking about vision is how your brain perceives it.
While the actual *Physical* focal length of the human eye is around 25mm, your brain take the stimulation from the cones and rods and maps it out and distorts it such that it looks to be closer to 50mm.
Your vision is something your brain does a lot of heavy lifting for, like how it removes the hole in your vision where your optic nerve starts, or removing your nose when looking forward, or filling in the blanks of your periphery when you're not looking at something directly.
A fun (and funny way) I found to really test out the weird things that happens to your vision when you push it to the extremes is this:
Have someone that you're close to (spouse, partner, sibling, or close friend.) Close one of your eyes and, with your open eye, put your face right up against theirs with your eye centered on the very top part of where their nose starts.
If you keep your center vision focused there but then try to focus on your peripheral vision, you'll notice that you can still actually see both their eyes and even past their head, but it almost looks like an extreme fish-eye effect. Your eye, even less than a half-inch away, can not only see someone's eyes and cheekbones but even past them as well.
When you see do this you actually get to somewhat really perceive how wide your FOV truly is (more akin to the actual 25mm distance) but in normal day-to-day activities and with both eyes your brain reformats your vision seamlessly to look like that 49mm-73mm range.
The question isn't "what is the focal length of the human eye?", its "What's the ***perceived*** focal length of human vision?"
yep, this. This is the real info that should be in the video.
I like the focal length of 40mm on my m43 Olympus camera, especially the Lumix 20mm F1.7 lens which has a 40mm with 4/3 aspect ratio.
Thanks for breaking down this issue in such an easily digestible way! I always get annoyed when people claim that this or that focal length is how the human eye sees - when we obviously have a really, really wide field of view, but can also focus our attention to a part of that field of view.
One thing that I was missing from the discussion (maybe something for a follow up video?) is the fact that perception of focal length changes with the size of the image we're seeing, or the distance respectively. Anecdotal evidence: when I first put a 35mm lens on my A7C and looked at the image through the abisally small EVF, it felt really unnatural and weirdly wide angle to me. Not so with other cameras. And when I put a 5.5" monitor on my camera, all of a sudden 35mm feels entirely different. When I view 35mm footage on my computer screen, it feels different yet again. And if I had the ability to stream an image directly into my brain, it would feel different yet again.
That's why I love Pentax FA 43 so much.
Thank you for not going to the click bait rout and getting to your point in the thumbnail. That alone made me sub. Interesting, well made video.
Leica actually made a 40mm summicron C for the CL cameras. It’s M mount and quite affordable. Not may people use it because no M camera has the 40mm viewfinder lines.
I like to think 43mm is. That’s the diagonal of the 36 x 24mm frame. Pentax has long had its 43mm f1.9 many have considered the ‘true normal’
My first 35mm camera was an Olympus 35 SP with a 42mm lens. I came to realize after many other cameras, that I liked to 42mm perspective on full frame. Unfortunately, not too many prime lenses in the 40-45mm range for full frame digital cameras.
Pentax FA43/1.9
My favorite Nikon zoom lens was 43-86. Of the fixed lens rangefinder cameras I have, only the Olympus SP has a 42mm lens. Great video, love your explanations about the eye in relation to focal lengths!
Excellent video 😊!
Best video on this topic I've seen so far
This is probably the best video on the topic of 'natural focal length' I have seen. Great job!
For me the most natural representation is between 70-90mm. 40-60mm with still somewhat useful peripheral vision. Wider focal length is just a danger/movement detector with no meaningful resolution.
Thank you!
It's 43.27mm which is the diagonal of a full frame sensor, as the eye is a sphere it roughly approximates the relationship between flange distance and focal length of the eye ball
Actually Leica does have a 40mm M mount lens in collaboration with Minolta for the model CL, it’s also my only owning Leica M lens at the moment
What is this music
I did an experiment with a 20 to 70mm zoom lens where i carefully observed a street scene without focusing on any particular part. So just look straight ahead and noticing what was clearly in focus without moving my eyes around. I thought i was going to end up with 50mm as that is what i had been told for years was the normal vision. But for me the closest was somewhere in the range of 30 to 35mm. I still find 35mm the most normal looking focal length...but i also wonder if thats just years of looking at newspaper photographs growing up
music name : Will Rosati - Lonely Troutman II
For *Close to Far* (how far things are from each other and from the viewer), the 42mm is indeed closer to how human eye perceives distances. But not in terms of "how much of the scene" we see (field of view). If you hold your hand next to your head, your peripheral vision still captures it (almost fisheye field of view but not sharp). I would say the human eye is "an almost fisheye lens corrected like a 42mm for distance perception and distortion".
Really well presented info. Thanks for taking the time to pull that all together and share it so well.
this explains a lot. ive always considered the argument of eyes to focal length is corner to corner and it felt about the same as an eq 18mm lens i used, hearing people say your vision is about 50mm really started to confuse me! very educational video
actually this video completely misses the main point, that being the 50mm gives you the same perspective of human vision, as far as distance, compression of view goes, it doesn't give us the same field of view, but gives us the same perspective, where as 18mm flattens out the image and distorts it in a way our eyes do not.
Very good film, very informative, light on boring stuff, to the point. Thanks!
Aamazing video!
Just to be correct, Leica did have the summicron-c 40 f2.0 lens, it also came as minolta rokkor 40/2. Amazing little lens.
One rule of thumb is that a “normal” lens would have a focal length equal to the diagonal of the sensor. In the case of full frame, that is about 43mm. If you use a camera with a different aspect ration, such as 4:3 medium format, it is not so obvious what the focal length equivalents should be. Using the relative diagonals is a compromise, and sometimes you may want equivalent width or equivalent height. My first 35mm camera had a fixed 45mm lens, so that looked normal to me out of habit and experience.
When I look through an old film SLR where the viewfinder is designed to appear at 100% magnification, the image I get with a 50mm lens focused toward infinity matches/lines up with the image that I see with the other eye. 50mm, give or take, seems to produce the same compression and angular perspective as human vision.
Nice. I’m a Leica M user, and always appreciate great optical quality. And… my latest purchase, the Hasselblad 55V is 43mm in 35mm measurement… Perfect 😅
How about the Leitz Summicron-c 40mm f2 and the Summarit 40mm f2.4? Aren’t they close?
And what About sensitivity of human eye compare to iso sensitivity? Is there any reseach?
That was very interesting! Works in photography too. And it explains why some photographers prefer 35 mm as their "go-to" focal length, some 40 mm, or 45 mm, or 50 mm (or even 55 mm). I'm comfortable with 35 or 50 mm, more leaning to 50 mm (for me it's more about details).
Interesting! Thanks!
Let me just ask, because I don't get it: How is the grey "full frame 36x24mm" frame in the diagrams taller than the blue "full retina 40x27mm"?
I think that was a mistake.
@@wolfcrow A truly informative clip, nevertheless! Thanks again!
@@wolfcrow Thanks!
For me, there's a combination between sensor/emulsion size vs lens. And the answer is quite simple and not subjective. In a normal lens, when you look through the lens while keeping both eyes open, you should see no change in perspective, meaning the size relation between near and far objects. As a guide, you should be able to walk with no problem using the normal lens while viewing through the viewfinder, and then the lens, and you should feel no change at all between both eyes. The confusion starts by the fact that people use the same language for different things ("35mm format", or "35mm film") Full frame is one thing while Super 35 or cinema 35mm format is a different size. Hence, when looking through a stills photo camera the "normal lens" is around 80mm; in 35mm cinema film cameras is around 50mm. So it's not a "democratic" thing, but a real fact. Human vision is quite wider than what you can see through the lens, but as the purpose for this is to capture images as we see them, the whole idea is to be able to capture the relation between the things in front of the camera as we see them in relation to each other, in disregard of the full wide view that our brains render.
SMC Pentax-FA 43mm F1.9 Limited. Sadly mine is broken.
Best natural feeling from the focal length I ever had was from EF-M 22mm f/2 on Canon´s APS-C, it was specifically designed lens for crop sensor.
What about lens compression? What focal length and at what distance is closest to the human eye? when using 15-22 or even 35 I don't see the same compression
Appreciate this. I’m relatively new to photo and found 35mm to be a relief but not quite there, and on the high end I don’t have the budget to figure out why my 135mm isn’t narrow enough, but 200mm photos online don’t do it for me either. I’ll have a better chance at finding my ideal lenses now.
Is there somewhere we can see a list of the films used during your video? Looked like some interesting frames! Love the 40-45mm lenses, Canon, Leica, Minolta and Pentax make some stellar examples! Thanks
Question: Does shooting on a crop sensor camera (such as Canon, at x1.6), with a 28mm lens, get you close enough (44mm)? or am I wrong?
Focal length of one human eye is 50mm with an aperture of F2. The combined focal lenght of human vision with our two eyes is 24MM also F2.
An immaculate video! +1 subscriber here
Always tricky to determine focal length when trying to render out a human view in 3D, so perspective looks correct, especially useful when trying to figure out optical illusions
Most of this is missing a very important point. When we have the correct field of view (the AREA in view) the objects are not the correct size as seen by the eye. The correct focal length for size to match the human eye is 58mm. Just put a camera with a 50mm lens on it up to your eye and look through the viewfinder, at the same time open the other eye and the differnce in size can be seen,50mm too small, 58mm correct size.
Please share the link to the article you mentioned in the video which goes more in depth 👀
Wooooow superb video. More n more thanks sir n all teams ❤️💐🙏🎂❤️🙏.
I wonder, waht is the maximum and minimum aperture of the iris in f/stop equivalent terms?
I like to speak of the eye-brain-system which has to be imitated by the photographer or cinematographer. The unfocused view is very wide, the focused view on details is more tele.
This video is a great visualization and explanation of that, and now I see my thoughts confirmed. Thanks!
EDIT: And the video stands out because you say that we shoudn't be religious with the 43.0000 mm focal length!
28 on a 1.5 crop sensor is 42, and that's a pretty easy combo to find. I think that's one several street photogs prefer.
thanks bro
50 was always narrow for me
35 quite perfect
but it’s time to 40-45
by the way what is the b&w movies clips you use here?