Is your lens REALLY in focus?
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- Опубликовано: 13 сен 2024
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Welcome to Lensdays! This video is about seeing field curvature in any lens. The better you understand the photography equipment you own, the better you're going to be able to express your artistic vision and intent. Most photographers understand how depth of field works, but most don't understand what its actually doing in lens that they are using. Some lenses exhibit field curvature which can make you think things are in focus when they are not. Its also important to understand how depth of field works at scale. An f-stop of 2.8 is much wider the further from the camera you focus. So how can you visualize this? I have a trick for you.
Watch more Lensdays! • The TRUTH about Lens D...
Lenses used in this video - Canon 24-70mm f/2.8L, Sony FE 35mm f/1.8
Check out Roger Cicala's blog post on field curvature www.lensrental...
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On my channel you will find videos about photography, cinematography, post processing tutorials for Capture One, Lightroom and Photoshop, photo assignments that YOU can participate in, the Artist Series and more. The Artist Series is an ongoing set of videos I produce as documentaries on living photographers. I am extremely passionate about photography and video and my goal in making these videos is to share my passion and enthusiasm with you! Don’t forget to subscribe and make sure to hit the like button and share this video if you enjoyed it!
Ted Forbes
The Art of Photography
2830 S. Hulen, Studio 133
Fort Worth, TX 76109
US of A
I love your 'nerdy' approach! It feels so good to have a good educator on RUclips that doesn't want to explain why you need a 100$ LED panel or something like that. Great work!
Just a note, if you want to understand why a smaller aperture gives you greater DoF, it's like this. As you're stopping the lens down, you're blocking out the diffuse light, coming in at weird angles. As that light is blocked, you're basically raising the signal/noise ratio of incident to direct light. Obviously, you have less total light, but the light you're actually seeing is focused. In other words, as you open up the aperture, the out of focus light is drowning out the in focus light.
You are truly one of the best instructors on RUclips... I have subscribed and look forward to more of this type of in depth discussion!!! Thank you ever so much for being so open with your knowledge...
I agree totally! I'm subbed to a few photographers on RUclips but Ted is by far the best at making you understand the more complex aspects of photography! I could listen to him do hour-long videos on anything photography related. He seems to be one of the only folks that also enjoys to educate you on the classic photographers. I had never heard of half of the classic photographers until I started watching Ted.
Great tip on the ‘film format’ setting on Fujis. I’ve just changed all mine over to that setting. I did always think that the DoF predictor bar was uber-conservative. Now I know why! Thanks Ted.
In the old days, back when I used film I used the same gestimate technique on my old canon t60 camera with zoom lenz for focusing. God that demonstration brought me back.
Very grateful that we have people like you !!! Thank you !
That entire field curvature phenomenom really sheds some light on edge sharpness
Wow. Never have I seen the DOF explained so clearly yet so simply as its done here. Will be recommending this video to all my friends who could benefit from. Wonderfully done, thank you!
Thank you Ted. As usual, your educational content is excellent. Merry Christmas.
this is a FANTASTIC visualization of field curvature. thank you!!
Seriously amazing videos! Please don't stop. It's great to have amazing and experienced photographers like you explaining this stuff to less experienced folk like us!
Wow, never heard of field curvature before. Thank you so much for making me aware of this. Especially important for me as someone who loves to shoot open.
New fan alert! I absolutely love your videos!
Great episode again Ted, thanks. I love using all my manual vintage Carl Zeiss Jena DDR lenses on my X-T3. They all feature the handy good old DOF scales and are just beautifully crafted.
I'm so glad I've found your YT channel - I was looking for information on field curvature and you've provided the clearest way to show it even if it's not scientific, that doesn't matter, the technique gives me what I need to know. Thanks so much for the explanation and I really must check out the rest of the Lensdays series.
Great series. Grateful for the tip on the overlooked tool/setting in my X-T3. Looking forward to your next one in the series.
A simple observation: landscape painters go to great lengths to learn how to create soft edges for objects in the distance. This is done to provide the the viewer with illusion of distance on a flat canvas. It is often unnecessary, and even detrimental, to obsess over trying to obtain maximum depth of field.
Yes, this is true, but the point of the video was more about how to know for sure what DOF you have, therefore to be in control of it. The amount you use is up to you. On a side note, I too wish all lenses have a DOF scale, but I guess I come from film so I'm kind of used to it.
Really enjoying this series of videos Ted!
I was trained as a physicist so I know the theory behind this, but that visualisation using 'Find edges' is a very neat trick for which I'm indebted to you. Excellent presentation of an important subject.
Loved the information especially the use of photoshop to check the focus line. Have a Merry Christmas and Happy New Year!
great trick there I never knew about that Ted. Always great content. keep it up. looking forward to more of this series on lenses.
Wow - mind blown. Excellent food for thought Ted. Love the implementation in the X-Pro 3 you demonstrated.
Great video! I learned a couple of things about lenses, now I'll start testing them all.
Great Video Ted. Appreciate your way of explaining things :) That find edges filter is quite a useful tool to figure out curvature and now I understand what the 'film format' DOF scale is in my Fuji! Keep em coming and wish you a very happy new year!
Great job! I used to love the dof scale on the old Nikon push pull 80-200 zoom. The graphic was really really useful.
Great episode! I'm glad someone is providing information on this. It used to be somewhat common knowledge.
The focus range on the screen is perfect. Yes, they all should do this.
Came here from Peter Mckinnon, this is very informative. Thank you sir !
such a great way to visualize field curvature!
These markings can also be found on some of the Fujifilm XF prime lenses like the 14mm f2.8, the 16mm f1.4 and the 23mm f1.4. You can also use some older Nikon Ai(s) or Canon FD lenses with a adapter using the hyper focal distance when landscaping or in the streets. Zone focusing is just as easy. Thus creating a point and shoot camera witch can make you a faster street shooter. Just keep going old school is sometimes a lot faster and simpler in the field. And no calculations or DOF calculator needed. ;-)
Great explanation of the field curvature. Now I want to check out my lenses and see how they perform. I'm with you on the lens DoF markings. That's one of the biggest things I miss from when I had my Pentax film cameras.
Going from 35mm film to digital messed up my focal length understanding. It used to be normal eyesight was represented by a 43mm lens. Now depending on your digital camera's sensor, it might be 28 or something.
Thank you for the explanation of the two settings for the depth of field scale. I have a Fuji camera and have had the depth of field scale turned on, but it was set to the default of the pixel level. I did not find the very useful. By changing it to the film level I can already tell it will be much more useful.
I have always wondering what are those extra numbers printed on the lens, now I know. This video is really helpful.
Great video Ted. Reminding me that there is still much to learn. Thanks!
Everyone should understand Hyperfocal distance...
Enjoying these technical vids 👊🏻
for landscape i use focus peaking to show the depth of field
I really love your channel, Ted!
Great video Ted, I really learned a lot of new information from this.
Great video, I'll have to test my lenses to see if they have field curvature. What kind of pictures do you think will benefit from it?
Thanks Ted - very informative. Can you explain Hyperfocal Distance focusing in more detail.
Thanx a lot man! This will really help me get a better understanding of what may actually be in focus. 👍🏻
also great for street photography to have a zone focus on ur lens.
My Zeiss 35mm f2 lens for M-mount has even more aperture markings for the depth of field scale and it’s so great to have. Leica lens also have my favorite depth of field scale and I wish more lenses in general had them.
Excellent! you absolutely nailed it..
Dug this video a lot. Thank you for posting it!!
Great way of showing field curvature of any given lens. I like to use a 12-24mm lenses kit to shoot architecture and panoramic scenes. I have some cameras with Depth Of Field Preview button, some are SLRs and some DSLRs. In fact, I chose a Nikon D7200 over a D7500 because of this feature and two others (two card slots and Non CPU Lens full compatibility). By the way, almost all analog lenses have a scale that shows DOF.
I wish could find a DOF calculator that worked backwards, meaning I put in the DOF that I want and it tells me either the distance or Aperture setting I should use (within the range of my lens).
Great video Ted, very clear and concise. In fact, it is very timely for me as I had an issue today whilst shooting portraits at an event. I noticed that in some of the portrait images of say 2 people stood sde-by-side, one would be in focus and the other was out of focus, even though they were pretty much on the same 'plane'. I was using a Nikon D7500 with a Tamron 28-75mm F2.8 lens. Settings: Mode-Manual, Shutter speed-1/200th sec, Aperture-F2.8, ISO 400, Metering-centre weighted, Pop-Up Flash used for all shots, single point AF (tried to focus on one person, hold shutter and re-compose). I was pretty close to all subjects-maybe between 1-2 metres away. Not sure if it is lens curvature, bad technique, AF not nailing focus properly, depth-of-field too shallow, or even poor quality UV filter that was on the lens. I have just opened an image in Photoshop & applied the 'find edges' filter as you did in the video & it does show the sharpness more clearly on the person on left (in focus)-maybe the person on the right was a bit further forward, but not much. I did notice that odd occasions the camera would not let me take the pic as my AF is set to focus priority in custom not release. Any ideas?
wide angle zooms (like 11-16, 24-70, 17-50, etc) had worst geometric corrections (fields curvature en the ends of the range) than prime lenses, it´s "normal". The only way to minimise that is closing to a smaller aperture , or focusing at long distance, moving away from the group a bit
that's why a 24, a 20mm "perfectly rectilinear" is more expensive than a zoom
Hello Ted. I bought a Fuji xt30 about a month ago. I shoot mainly flowers,macro,abstracts...mainly static images. I couldn't afford the 18-55 kit ( wish I could) so I opted for the 35mm f2. I absolutely love the images ,when ,they are in focus and not soft. I generally stop down to 4 or 5.6 in order to keep some broken and subject separation. I have noticed that this doesn't seem to be the right tool for getting those outside, down and low,in the grass shots. A lot of them are oof no matter WHAT I do and just when I seem to get the focusing figured out, it changes up on me! I use the back dial to press it in and it magnifies my subject. Then, I manually focus my lens and take the shot. The next time I try to use it,I turn the focus dial on the lens and IT causes magnification and throws me off! I came from Canon but wanted to try Fuji.I am in love with the vintage look of the photos but I think it's more for street photography and maybe candids . I'm thinking about sending it back for the Canon 6D m2. I've never used a full frame camera but I know I miss my bulky DSLR. Am I using the wrong tool or is it just me not knowing giving the Fuji enough of a chance? I also need a different lens, in my opinion. I knew about the dof setting in the menu but Thanks for the video!!
You can have beautiful focus line in mirrorless camera when you are using focus peaking on manual mode. Anyway, another good video, thanks :)
Coming from a background of fully manual film cameras and lenses I definitely miss the markings on the outside of the lens for focal distance/range.
So helpful, thank you.
Thank you, I never saw the curvature of the focus plane explained and visualized that way.
One of the most used phrases in lens tests is that the lens is loosing some corner sharpness when used wide open and that this gets better if you stop down the lens. According to the curve at 5:20 there is probably a lot of corner sharpness but it is in a slightly different distance. So this is only a problem, if you take a picture with different objects in exactly the same distance with very shallow DOF. If you want to take a picture with one object at the edge of the frame that has to be in focus, you get probably a much better corner sharpness. Unfortunately, this is never tested in normal reviews, so you don't know how good the lens is unless you get one and do your own test.
Great video! Thanks Ted!
I hate the minimalist trend, you did not mention focus peaking in manual mode. Love your videos!
Peter McKinnon suggested your channel. Informative video, thanks :)
Another great video and advice. We dig the “Lensdays” too!
Awesome rundown, Ted. And, as you know, I'd like to add that all the Zeiss Batis lens for Sony also have a DoF scale in the OLED strip at the top of the lens!
You've given what's probably the most useful explanation of hyperfocal distance without actually saying "hyperfocal distance."
A very interesting video. 👍 I didn’t know that you can set that in the Fuji menu, thanks for the hint.
I wish everyone a Merry Christmas and a Happy New Year. Greetings from Germany
Wow I didn't know I could do that on my fuji. Thanks Ted and Happy Christmas.
Excellent informative video
that was very interesting. Learned something new today. Thank you!
That's amazing, thanks for sharing
Great video, thanks!
Wholly smokes! I feel like I need a class just on this video alone. A lot to take in. Thanks for the info.
This content is so damn good. I love it. 11/10. Keep this up.
Enlarger lenses, graphic arts copy cameras, and special flat-field lenses (i.e. the Nikkor 45mm GN lens designed to be used with strobe lighting IIRC) were all designed for flat field focus instead of curved field. It is a design choice.
Great vid! By the way I think the street surface was asphalt.
The technical markings are missing except on some AF lenses with a focus clutch, because the focus ring on most modern AF lenses does not have a fixed correspondence between focus ring position and focus distance.
Educational and insightful - great presentation
Mentioning the “brick wall test” in the context of field curvature got me thinking about general statements about a particular lens having “soft corners.” I wonder how often the “soft corners” comment lumps in lenses that have some field curvature that results in the corners or edges simply being out of the focal plane (or curve) rather than being entirely soft.
First thing I thought of as well. So for a proper test you should probably put you focus point in the corner
Tom Unless you are photographing flat subjects head on a bit of field curvature does not matter, but if the lens still has soft corners at f/5.6 or f/8 at infinity it’s probably a different issue.
Very interesting. I'll give that a go and see what my lenses are like and if I get run over!
Nice video, never thought of that function in Photoshop ! On both pictures of the road, the sharp zones were tilted (going upwards to the right), could the lens mount be slightly unparallel with the sensor ?
I would love a focus scale for when I'm shooting starts at night. Sometimes I'm a hair off and it can be difficult to get it spot on, especially since I'm shooting wide open to keep my ISO low.
Unfortunately the dof indication doesn’t work on the x-t3. I tested it with the 23, 50 and 90mm f2 lenses. Even the manual says that it should work like you said, it doesn’t work. Bug?
Update: do not choose large icons on screen and evf! -> Not displayed when ON is selected for DSCREEN SET-UP > LARGE INDICATORS MODE(EVF).
I personally calculate each lens' hyper focal distance based on circle of confusion being set to the pixel size of my sensor when shooting digital or the film's grain size when shooting on film. This goes against manufacturers calculations, but this will give me numbers to base hyper focal focusing pushed to the limit of the sensor or film.
Simply, if a lens is set to focus at it's hyper focal distance, the depth of field will keep everything from infinity to one half of the hyper focal distance in focus with an error not exceeding the size of the circle of confusion.
I know actual images are not totally focal error free, but it gives me the starting point I want in my images
Nerds rule. Good video. I too miss DoF scales. It seems that cameras could have a setting to focus at the hyperfocal distance.
Vintage lenses by Schacht Ulm had a mechanically operated DoF scale. Depending on aperture a red bar/stripe would cover what's not in focus and only reveal the depth of field. Very easy to read quickly.
I hope my lens is in focus!
Well, that was fun. Thanks! You didn't show it, but most mirrorless cameras now have focus peaking. This gives you something like the edge-finding filter in Photoshop. However, it gives it to you when you are composing an image, which is where you want it if you want to get an image "right in the camera". It is also a good example of why the EVFs of mirrorless cameras are potentially so much more powerful than the OVFs of DSLRs. The commonly-available manual-focus assist magnification also helps in this area. As the computer chip in your cameras gets more powerful in successive product versions, this advantage will increase. Fuji's ability to give you a heads-up display of depth of field is another example.
The depth of field display does bring up another point, which is the issue of the tradeoff between blur spot diameter and sensor pixel stride. As you point out, perceptually perhaps the 30 micrometer blur spot diameter from the film days is more sensible that, say, a 5 micrometer blur spot. To within a factor of perhaps two, a 30 micrometer blur corresponds to an effective full-frame sensor resolution of about 1 megapixel. A 5 micrometer blur spot would correspond to a 36 megapixel sensor resolution. For APS-C, the equivalent resolutions would be about 1/2 megapixel and 18 megapixels, respectively. To me, this all adds to the mountain of data indicating that we all take sensor resolution way too seriously.
Really loving this series sir, also is that the 85 1.4 AI in the thumbnail.
Well obiously it is, its literally written on the front of the lens
@@jordon6855 derp
@@jordon6855 I don't see the AI (or S) on the lens image - just the MM and f, Nikkor and Nikon. I know from the period that it was likely AI, don't know about S. img.ruclips.net/user/vivcCWoh0f8PE/maxresdefault.jpg
thank you soooo much for the lens markings explanation... it is so simple and now it makes so much sense
I have a manual Irix 15mm f2.4, the aperture is camera controlled but the focus is full manual; with this information now I have a better understanding for the next time I use it!
Great video. Even on my Olympus EM10 I usually have a vintage manual focus lens on there and for things like street photography and candid portraits zone focusing and DOF scale are definitely handy. I think alot of manufacturers now just assume everyone uses AF.
Great ,thanks~
What you forgot to mention is that the depth of field not only varies with the aperture, but also with the focal lens of a lens. A shorter focal length (wide angle) has a much wider range of in focus than a longer focal length (tele) across all aperture settings. So what you've shown on the 35mm lens looks very different on a 200mm lens.
dude thanks so much for this video i was almost ready to give up on the XT3 and crossover to the Sony but this helped me. thanks
As a general rule, I just expect all standard purpose lenses to have field curvature, even very high quality lenses. Maybe it’s less of a thing now than it used to be? I dunno. I just know that when I need flat field focus, I grab a macro lens since that’s largely what they’re designed for. I’m actually a little surprised that you didn’t introduce macro lenses in the context of flat vs curved fields of focus. Valuable video though. I learned through failure about field curvature and wish I would have learned through a book or video or something instead and saved myself a bit of time, trouble, and money.
I learned today!!!!
Is it really the distance from the lens that determines focus or distance from the film plane?
This video should be in everyone's photo taking tool bag, it's in mine from this point onwards
What a great video Ted Forbes! Funny when I first got interested in Photography my Dad used the term Depth of Field and I remember being so confused by it.You've done a fantastic explanation of what it is plus with all the Technology available now you were able to show us even more. Thanks for loving Photography so much and for sharing such great information and knowledge through your channel!
Is there a way of finding the edges like in the photoshop example, but in capture one?
On Pentax cameras it's possible to se the DoF, I have no idea how accurate it is, never used it. Just remember I saw it some time. The function is available at least on K1, K3 and K7.
Thanks for really good videos. 😀
Beautiful video. Thanks for the interesting insight! I've always had a logical gripe with how the notion of DoF is used in English, which is counterintuitive for beginners in my opinion. The wider the aperture, the _more_ the field gains in depth - as an optical phenomenon. On the contrary, the narrower the aperture, the less depth the optical vision displays.
Never understood why is it used on the contrary. Or better, I do understand why - as in the field itself is imagined as a flat plain that varies in thickness with the aperture - but still, shouldn't a wider aperture give back a _deeper_ field (as in with more depth) to the viewer?
Some of the manual lenses made today do have those markings. Lenses what do focus by wire would have no real chance of being this accurate - try manual focusing at night with such a lens.. I expected to see a mention on focus peaking in this video, as it is a very good representation of the focus plane and DOF.
Good job Ted.
Excellent presentation, especially loved the fine edges part.