I'm a Metrologist witch is Calibration and repair of instrumentation. You did a fine job. I used a bulb that was calibrated at NIST for just the same type calibrations. Good job.
To find equal lumen value between two incandescent bulbs without having a meter you take a piece of tracing paper or what we call onion skin paper. Place one drop of mineral oil on it. Slide the paper between the two lite bulbs and you will notice the stain will stand out. Adjust the voltage of one of the bulbs until the stain disappears and you will now have equal lumen values. I learned this online from an Old Timer and was fascinated by the simple theory.
I searched high and low, you are the only person that answered all my questions. I just got a par meter today and was wondering light distance from light source to my meter. 11 inches. I figured 12 so I was close. Ty so much
I've watched a lot of youtube videos on Lumens & Lux and the majority were fairly useless. When I came across this video, I realized Julian knew what he was talking about, was able to present his approach in a very methodical manner, and summarized his findings brilliantly. I wish all videos were this refreshing and factual.
I went down the path you are on quite some time ago and ended up publishing a couple articles of "layman's guide" to understanding light and light measurement. I could probably save you and others some hair pulling as you wade into the silly jargon of illumination. The articles appeared in various US & UK amateur radio magazines in 2000. I will be glad to send you a copy or post it on my github if desired.
Ok, I did a bit of an update on it and put a copy in my public github repository for download. My github repos are TxNgineer and this article is at github.com/txNgineer/good-nuff/blob/master/articles/Luxes_and_lumens.pdf Hope people find it useful to demystify lumens, lux, nits, candela, f-stop, and other such stuff. You can do all the math in it with a calculator and notepad. It was targeted towards an amateur radio audience, but if you think in terms of WiFi you will get the point.
Your light meter is similar to my own so it may have an adjustment feature which will allow you to calibrate it and is ideal for when there is some ambient light in your test area. Set the meter up, adjust the reading to zero and then switch on the light source under test.
I use a similar meter to get the light even on a photographic copy stand. The sensitivity of these meters to slight differences makes it quite precise in this application. I also use it to get a sense of the brightness range for studio lighting. Nice to see some math deployed in checking out the claims on light bulbs.
The problem is that people think of Lumen/Lux considering a "flat" surface to illuminate (which of course is the real life situation) so radiation fall off is of course different when considering right under the lamp or at the edge of a square meter. besides light intensity drops by half when light source distance is doubled. The "overlooked" parameter is in the manual (video@10 minutes) where the radiation angle is correctly defined as 4pi sterradians which is far from a "flat surface" JFWIW
Never been any good at math. I was able to count may wages and my change from shopping, but square roots and bla bla bla was not needed in my daily thoughts until I watched this.Thx, nicely explained.
Light has lots of units of photopic (human visible) measure. In addition to lux and lumens, there's stilbs, entendue, actuance, nits, phots, candelas, lamberts, blondels, skots, and brils. 💡💡
Did you measure the 282mm from the surface of the glass 'bulb' or from the edge of the LEDs themselves? That extra couple of mm might make all of the difference! ;)
Correct me if I’m wrong, but is this not like trying to measure the amount of light being detected on the service area of a three-dimensional space by using the correlation of distance and a two dimensional space, that’s much smaller (a.k.a. the photodiode). The measurements would never be close to the same, right? The large 3D surface area of the sphere will always pick up a lot more light than the smaller 2D surface area of the photodiode. I’m sincerely asking, not trying to be rude. It’s been a while since I’ve had to do math so I could be off base 😂. There’s other things that we’re going to play such as how focused the the light is, the angle of the in relation to the photodiode, the distance the latest from the photodiode, ect. In my opinion you’d be better off grabbing a white trashcan or Styrofoam cooler that’s laying around the house and sticking the lux meter in there, then shining the light so it can bounce off of all the walls to get your reading. This still wouldn’t be an accurate or scientific representation of lumens but if you wanted a makeshift way to do it without having to leave the house I believe this will be the way to go. Also, I don’t think you could measure. How are you lumens using lux right? What did you use foot Candela? Again I could be completely wrong. I’d love to hear feedback.
Thx Julian. A problem I’d come across in the past and at that time concluded that I needed special equipment and a rig to achieve a meaningful measurement but your method looks straightforward and achievable. Well done that man!
I have one of these as well. What I´m most suspicious about in regards to its readings is how well it takes light color/wavelengths into account. For example it conveniently fluoresces under 400nm causing it to read much higher than it should.
I liked the somewhat shocked "I don't need to close the brackets..." with the calculaty-bit. Haha! It's also funny how light seems to BEAM out of the top (well, bottom...) of the light bulb as you explain about the shadowy spot. Lovely video and i don't mind it's not scientific. Still interesting.
Also measure the power to see whether it's really only 6 watts. I'm curious about whether it really gives 10 times the light per watt of an incandescent -- that sounds a bit optomistic to me.
as far as i know lux is a effort unit and lumens are a flow unit (as volts is a effort unit and amps are a flow unit) if your meter is measuring in lux its similar to measuring the voltage, your readings vary with the distance bc you can think of your bulb like of a ball that emitts discrete beams of light and the closer to the bulb you measure the higher the desity of beams ie more lux. tldr : the measurements make sense!!! edit: looked more of the vid... glad you sort of found out your self
What an interesting exercise! I always wondered how these meters were supposed to be operated. Perhaps you might have even been closer to the box's stated Lux figure given potential mains voltage differences at your house vs the test condition(s) at the factory?
If you can't get use an integrating sphere, you really need to study "steradians" (solid angles--you will love it!--It's like angles for a sphere rather than a triangle). Put a simple reflector around the light source as you use it here. I made a solid sphere out of wax and have ONE steradian of it sitting beside it--a cone with a spherical shaped big end that tapers to the point at the center of the sphere from which it came. Thanks for the video!!
This will only be true if 1. The light bulb radiates light equally in all direction 2. The light bulb can shine the whole surface area of a sphere (equally), including the bottom part of the bulb. (Assume bulb is in the center of sphere) 3. This is done in a dark room/black room. 1 and 2 will make lumen and candela equal in magnitude. No trouble in getting the solid angle. 3 will make the measurement accurate. Note that the reflectance will affect the measurement even if there are no other light source during the measurement.
It's easy to build an integrating sphere, it doesn't have to be spherical or highly reflective, a white box will do, but it does need to be calibrated with a known source of light. If you're not fussy you can use a 60W incandescent bulb as the reference and then just use that as your unit of brightness.
You cant necessarily base lightbulb comparison solely on lux. When it comes to reflector design, the biggest factor is the size of the light source. The light emission of the filament bulb happens on a much smaller surface area than some led bulbs. The reflectors in cars are designed to take advantave of this. Using led replacements with large emission areas and high claimed light output may actually yield terrible results, as the reflectors arent optimized for the larger emission area. In fact you may find that led replacements with lower lumens but emited from a single source on two or 3 sides will yield better results than a replacement with 10 xhp70 chips, that may melt the housing from all the heat :) In addition if you have 16 1 watt chips on a single led bulb replacing a 10w incandescent... well... do the math
You could use a std incandescent bulb as a sanity check for the meter. Still what you're measuring isn't way out in left field. WAY cheaper than an integrating sphere :)
Lux is a calculation of Lumens projected over a known area (as is foot candles). 1 Lux = 1 Lumen X 1 meter X 1 meter. If this device doesn't know what your distance is from the light source or the area of the surface it projects on, how can it measure Lux or Foot Candles? This is a Lumen meter. When the manufacturer doesn't know the difference, I don't trust the output it produces.
That likely isn't you only lux meter: your phone probably has one, and those are surprisingly accurate. Find an app that will show the reading and then you have something to compare with!
This was very helpful. Trying to measure the ideal distance my plants should be from a pre-determined lumen outputted system. Bought myself a lux meter thinking it would immediately translate to lumen output and of course I was wrong. Now I just need to figure out the math... ugggh, I suck at the maths. Thanks.
hi..i wanted to let you know that the flat green pad had caught my attention & i wanted to know what is it called because i myself will like one of those.
Measuring lumens by estimating it from one point is often very inaccurate. Light can have different intensity to different directions! It is usually measured by something like a diffusing sphere that makes the light level even and you can estimate total amount of light from one point. Led lights often have lenses built in and are more or less directional. The problem is easy to see if you take a directional light like a flashlight. It has very different output at the edge of the light cone than in the center spot. (And a lot more different if you measure it from the side or back.)
As you indicated, your calculation would only be meaningful if the output of the lamp was isotropic, which it clearly isn't. Another issue could be that devices are often calibrated against a known illuminant, such as tungsten filament lamp, and that will have a very different colour spectrum compared to your LED lamp. I touch on this subject a little at work and ended up making myself a little cheat sheet to help me picture the relationship between the different radiometric and photometric terms.
Hi Julian, since you have used the formula for the surface area of a (perfect) sphere and in your experiment if we ignore any actual bulb differences from an ideal sphere (plus spurious reflectivities etc) you will however still be a factor of around 2X in error because the light meter does not look at the entire spherical surface of the bulb but instead looks only at the surface of half a sphere (the maximum surface area presented to the meter at any one time), since the meter cannot look at the back and front of the bulb surface both at the same time. And yes you are quite correct about the cost of the meter being very expensive at around AUD$560.00! Interesting experiment nevertheless. Cheers from Down Under
The meter doesn’t have to be a sphere. Actually in this case it shouldn’t be spherical at all. The meter is set to measure the amount of light emitted by the light source to an imaginary sphere with a surface of 1m2. That happens to be at 0.282m of the center of the light source. This is assuming that it is emitting light equally in every direction.
And with a specific filament size. And this is why LED replacement lamps, which have light emitting surfaces that are enormous by comparison to the size of a typical halogen lamp filament, result in a huge amount of "spill" which blinds oncoming traffic. It's always going to be hard to design a reflector that produces an acceptable beam pattern when using any LED lamp. And this is why successful LED headlights use a lens arrangement instead of a reflector. LED replacement bulbs should probably be outlawed, and poor OEM headlamps that blind oncoming traffic should also be banned. For all of the potential good of LEDs as the light source for car headlights, lack of understanding, poor design, and lack of practical regulation has made them more of a menace than a benefit.
And what if I have a bulb with Lux units on the package ... What's the correct way to measure Luxes with this Uni-T unit ? BTW immersive video and science.
Ok. So the LUX unit is kinda tricky. Especially in terms the Bike LED lamp which I use - it's made by Busch&Muller - German manufacturer and they placed information on the package "90 LUX". But every bike has a different position of front lamp montage bracket, so it's a little difference in distance between lamp and road. That equals different LUXes amount.
Well manufacturers just print numbers on their product specs to make them look more technical and they put a bigger number on the more expensive product and a smaller one on the cheap stuff. Quite often the numbers just don't really mean anything.
The professional lab tool is called an Integrating sphere. It is the Only way to get accurate readings of what is described on the box or from a spec sheet. Lux and lumen are okay if all you need to do is measure visible spectrum rudimentary. Not to mention those testers are veeeery innacurate eveen in testing what they are designed for. Apogee instruments even though they are expensive. Light is serious business.
@@JulianIlett nice video but the information myhbe not correct because lumens is the sommation of all liggt emitted by the bulb you need to redirect all the radiation to your meter sorry for my english .
Typical retail LEDs are around 100 lumens per watt with accurate measurement. The best generally available are around 120. The best kit available on the business market exceeds 200 lumens per watt, focussed on the warehouse lighting market where lighting costs a lot of money.
You can measure lux using your Android phone if you have auto brightness in your brightness display setting Just install CPUz and click on sensors tab Boom You got another lux measurement device
I found these readings to be extremely inaccurate in most phones. I have the same meter as Julian and have compared it to the readings of 3 phones some time ago. The *BEST* reading was still around 30% different from the Uni-T. So to measure a lamp´s brightness, they are useless.
You can measure Lumens. Lux can be calculated by multiplying the measured Lumens by the square area of the projected surface. If it is a light bulb, the surface is a sphere.
Your formula for calculating the area of a circle is incorrect. It should be "A=πr2". It is not "A=4πr2". Not sure why I managed to remember a formula from my school days of about 4 decades ago, a formula that I hardly ever need to use, but there you have it.
He very clearly and repeatedly talks about the *sphere* that receives the light, not a circle. "Area = 4πr²" is the correct formula, for the sphere. He's calculating the radius of a sphere of area 1m².
Stop saying is not scientific, it really is, although not very precise. :) Additionally, the assumption under the 28.2cm is that the source of light is a point of size 0, so you should take into account the size of the bulb.
You can get a PS sphere or a white PVC pipe and accessories and make your own integrating sphere, into which you can put your DUT (in this case the light bulb) and the lux meter, and using a simple calculation you can get the lumens. See this: ruclips.net/video/xOE1ykJ5WAU/видео.html.
I'm a Metrologist witch is Calibration and repair of instrumentation. You did a fine job. I used a bulb that was calibrated at NIST for just the same type calibrations. Good job.
To find equal lumen value between two incandescent bulbs without having a meter you take a piece of tracing paper or what we call onion skin paper. Place one drop of mineral oil on it. Slide the paper between the two lite bulbs and you will notice the stain will stand out. Adjust the voltage of one of the bulbs until the stain disappears and you will now have equal lumen values. I learned this online from an Old Timer and was fascinated by the simple theory.
Fantastic!
That will be great to test with known light sources (calibrated) and see if it works with LEDs as well.
I searched high and low, you are the only person that answered all my questions. I just got a par meter today and was wondering light distance from light source to my meter. 11 inches. I figured 12 so I was close. Ty so much
Awesome, thanks :)
I've watched a lot of youtube videos on Lumens & Lux and the majority were fairly useless. When I came across this video, I realized Julian knew what he was talking about, was able to present his approach in a very methodical manner, and summarized his findings brilliantly. I wish all videos were this refreshing and factual.
Alhamdulillah,this is what i've looking for to complete my thesis,thanks a lot,i've got your point😍
I went down the path you are on quite some time ago and ended up publishing a couple articles of "layman's guide" to understanding light and light measurement. I could probably save you and others some hair pulling as you wade into the silly jargon of illumination. The articles appeared in various US & UK amateur radio magazines in 2000. I will be glad to send you a copy or post it on my github if desired.
Ron Sparks - publishing those details would be good 😀
Ok, I did a bit of an update on it and put a copy in my public github repository for download. My github repos are TxNgineer and this article is at github.com/txNgineer/good-nuff/blob/master/articles/Luxes_and_lumens.pdf Hope people find it useful to demystify lumens, lux, nits, candela, f-stop, and other such stuff. You can do all the math in it with a calculator and notepad. It was targeted towards an amateur radio audience, but if you think in terms of WiFi you will get the point.
@@txtigr Much thanks.
Your light meter is similar to my own so it may have an adjustment feature which will allow you to calibrate it and is ideal for when there is some ambient light in your test area. Set the meter up, adjust the reading to zero and then switch on the light source under test.
I use a similar meter to get the light even on a photographic copy stand. The sensitivity of these meters to slight differences makes it quite precise in this application. I also use it to get a sense of the brightness range for studio lighting. Nice to see some math deployed in checking out the claims on light bulbs.
Excellent coverage of the subject, making it easy for all to understand. Thanks!
Picked up a lux meter at a garage sale ages ago. Need to use it tonight. This video shall help. Thanks
The problem is that people think of Lumen/Lux considering a "flat" surface to illuminate (which of course is the real life situation) so radiation fall off is of course different when considering right under the lamp or at the edge of a square meter. besides light intensity drops by half when light source distance is doubled. The "overlooked" parameter is in the manual (video@10 minutes) where the radiation angle is correctly defined as 4pi sterradians which is far from a "flat surface" JFWIW
Really enjoyed that video. Very well explained in plain english. Thank you very much
Never been any good at math. I was able to count may wages and my change from shopping, but square roots and bla bla bla was not needed in my daily thoughts until I watched this.Thx, nicely explained.
Light has lots of units of photopic (human visible) measure. In addition to lux and lumens, there's stilbs, entendue, actuance, nits, phots, candelas, lamberts, blondels, skots, and brils. 💡💡
eek :)
I presume blondels are not very bright ....
@@blg53I see what you did there.
Did you measure the 282mm from the surface of the glass 'bulb' or from the edge of the LEDs themselves? That extra couple of mm might make all of the difference! ;)
Correct me if I’m wrong, but is this not like trying to measure the amount of light being detected on the service area of a three-dimensional space by using the correlation of distance and a two dimensional space, that’s much smaller (a.k.a. the photodiode). The measurements would never be close to the same, right? The large 3D surface area of the sphere will always pick up a lot more light than the smaller 2D surface area of the photodiode. I’m sincerely asking, not trying to be rude. It’s been a while since I’ve had to do math so I could be off base 😂. There’s other things that we’re going to play such as how focused the the light is, the angle of the in relation to the photodiode, the distance the latest from the photodiode, ect. In my opinion you’d be better off grabbing a white trashcan or Styrofoam cooler that’s laying around the house and sticking the lux meter in there, then shining the light so it can bounce off of all the walls to get your reading. This still wouldn’t be an accurate or scientific representation of lumens but if you wanted a makeshift way to do it without having to leave the house I believe this will be the way to go. Also, I don’t think you could measure. How are you lumens using lux right? What did you use foot Candela?
Again I could be completely wrong. I’d love to hear feedback.
Thx Julian. A problem I’d come across in the past and at that time concluded that I needed special equipment and a rig to achieve a meaningful measurement but your method looks straightforward and achievable. Well done that man!
I have one of these as well. What I´m most suspicious about in regards to its readings is how well it takes light color/wavelengths into account. For example it conveniently fluoresces under 400nm causing it to read much higher than it should.
I liked the somewhat shocked "I don't need to close the brackets..." with the calculaty-bit. Haha! It's also funny how light seems to BEAM out of the top (well, bottom...) of the light bulb as you explain about the shadowy spot. Lovely video and i don't mind it's not scientific. Still interesting.
How about comparing the led lamp with an old school 60w incandescent.
Also measure the power to see whether it's really only 6 watts. I'm curious about whether it really gives 10 times the light per watt of an incandescent -- that sounds a bit optomistic to me.
Thats actually my science fair project
1 Candela = 12.57 Lms is the best part.
as far as i know lux is a effort unit and lumens are a flow unit (as volts is a effort unit and amps are a flow unit) if your meter is measuring in lux its similar to measuring the voltage, your readings vary with the distance bc you can think of your bulb like of a ball that emitts discrete beams of light and the closer to the bulb you measure the higher the desity of beams ie more lux.
tldr : the measurements make sense!!!
edit:
looked more of the vid... glad you sort of found out your self
Lumen: How bright a source creates it's light
Lux: Brightness of the source on a certain distance
What's a foot candle 🕯️
@@AgentOffice Non SI unit of LUX
I'm sure there's a more technical way of describing it.
What an interesting exercise! I always wondered how these meters were supposed to be operated. Perhaps you might have even been closer to the box's stated Lux figure given potential mains voltage differences at your house vs the test condition(s) at the factory?
If you can't get use an integrating sphere, you really need to study "steradians" (solid angles--you will love it!--It's like angles for a sphere rather than a triangle). Put a simple reflector around the light source as you use it here. I made a solid sphere out of wax and have ONE steradian of it sitting beside it--a cone with a spherical shaped big end that tapers to the point at the center of the sphere from which it came.
Thanks for the video!!
Thanks for sharing your experiments. I guess there are also some phone apps that might be interesting to try too.
This is the most scientific video I've seen lately, excluding Cody's Lab ones.
Best way to start out my birthday when I sit down to a fresh posted video from you. Thanks mate, keep being awesome.
This will only be true if
1. The light bulb radiates light equally in all direction
2. The light bulb can shine the whole surface area of a sphere (equally), including the bottom part of the bulb. (Assume bulb is in the center of sphere)
3. This is done in a dark room/black room.
1 and 2 will make lumen and candela equal in magnitude. No trouble in getting the solid angle.
3 will make the measurement accurate. Note that the reflectance will affect the measurement even if there are no other light source during the measurement.
I've always wanted to know at what distance these lumen counts on the light bulb packaging was taken and now I know thank you.
It's easy to build an integrating sphere, it doesn't have to be spherical or highly reflective, a white box will do, but it does need to be calibrated with a known source of light. If you're not fussy you can use a 60W incandescent bulb as the reference and then just use that as your unit of brightness.
I am not a number, I have a name (which ever that was?) :)
You cant necessarily base lightbulb comparison solely on lux.
When it comes to reflector design, the biggest factor is the size of the light source. The light emission of the filament bulb happens on a much smaller surface area than some led bulbs. The reflectors in cars are designed to take advantave of this.
Using led replacements with large emission areas and high claimed light output may actually yield terrible results, as the reflectors arent optimized for the larger emission area.
In fact you may find that led replacements with lower lumens but emited from a single source on two or 3 sides will yield better results than a replacement with 10 xhp70 chips, that may melt the housing from all the heat :)
In addition if you have 16 1 watt chips on a single led bulb replacing a 10w incandescent... well... do the math
282mm is the radius, which extends halfway into the bulb. You need 282mm minus the bulb radius.
The source of the light isn't coming from the exact center of the bulb either.
You could use a std incandescent bulb as a sanity check for the meter. Still what you're measuring isn't way out in left field. WAY cheaper than an integrating sphere :)
Hello. Good thinking, but....this 0.282 is the diameter and not the radius......with whatever that might mean.! Good job
It's 2:00AM, I just finished editing my latest video, waiting for it to render. Julian, you're keeping me alive.
very useful - thank you (i´ve learnt this a felt hundred years ago and now i can remember this stuff)
cool with your lux meter, can you check to see if theres any smart phone equivalent? and if theyre actually accurate?
Lux is a calculation of Lumens projected over a known area (as is foot candles). 1 Lux = 1 Lumen X 1 meter X 1 meter. If this device doesn't know what your distance is from the light source or the area of the surface it projects on, how can it measure Lux or Foot Candles? This is a Lumen meter. When the manufacturer doesn't know the difference, I don't trust the output it produces.
That likely isn't you only lux meter: your phone probably has one, and those are surprisingly accurate. Find an app that will show the reading and then you have something to compare with!
This was very helpful. Trying to measure the ideal distance my plants should be from a pre-determined lumen outputted system. Bought myself a lux meter thinking it would immediately translate to lumen output and of course I was wrong. Now I just need to figure out the math... ugggh, I suck at the maths. Thanks.
hi..i wanted to let you know that the flat green pad had caught my attention & i wanted to know what is it called because i myself will like one of those.
Its called cutting mat board
28.2cm or 11.10” or 11” 3.5/32” to determine Lux
What about using one of these on my projector to correct the colour balance with test patterns?
Been looking for some filament led bulbs from a store . Will give these a go. Thanks.
Nice effort.
Does this method work on directional light source (i.e floodlight)?
Measuring lumens by estimating it from one point is often very inaccurate. Light can have different intensity to different directions! It is usually measured by something like a diffusing sphere that makes the light level even and you can estimate total amount of light from one point. Led lights often have lenses built in and are more or less directional.
The problem is easy to see if you take a directional light like a flashlight. It has very different output at the edge of the light cone than in the center spot. (And a lot more different if you measure it from the side or back.)
As you indicated, your calculation would only be meaningful if the output of the lamp was isotropic, which it clearly isn't. Another issue could be that devices are often calibrated against a known illuminant, such as tungsten filament lamp, and that will have a very different colour spectrum compared to your LED lamp. I touch on this subject a little at work and ended up making myself a little cheat sheet to help me picture the relationship between the different radiometric and photometric terms.
Hi Julian, since you have used the formula for the surface area of a (perfect) sphere and in your experiment if we ignore any actual bulb differences from an ideal sphere (plus spurious reflectivities etc) you will however still be a factor of around 2X in error because the light meter does not look at the entire spherical surface of the bulb but instead looks only at the surface of half a sphere (the maximum surface area presented to the meter at any one time), since the meter cannot look at the back and front of the bulb surface both at the same time. And yes you are quite correct about the cost of the meter being very expensive at around AUD$560.00! Interesting experiment nevertheless. Cheers from Down Under
The meter doesn’t have to be a sphere. Actually in this case it shouldn’t be spherical at all. The meter is set to measure the amount of light emitted by the light source to an imaginary sphere with a surface of 1m2. That happens to be at 0.282m of the center of the light source. This is assuming that it is emitting light equally in every direction.
Sr is a 2D angle of one radian per one radian.
The problem with LED replacements for automotive signal lamps is the reflector is designed to work with a specific filament location.
And with a specific filament size. And this is why LED replacement lamps, which have light emitting surfaces that are enormous by comparison to the size of a typical halogen lamp filament, result in a huge amount of "spill" which blinds oncoming traffic.
It's always going to be hard to design a reflector that produces an acceptable beam pattern when using any LED lamp.
And this is why successful LED headlights use a lens arrangement instead of a reflector.
LED replacement bulbs should probably be outlawed, and poor OEM headlamps that blind oncoming traffic should also be banned.
For all of the potential good of LEDs as the light source for car headlights, lack of understanding, poor design, and lack of practical regulation has made them more of a menace than a benefit.
And what if I have a bulb with Lux units on the package ... What's the correct way to measure Luxes with this Uni-T unit ? BTW immersive video and science.
It won't have Lux on the package - because the amount of light falling on a surface depends on how far away the bulb is.
Ok. So the LUX unit is kinda tricky. Especially in terms the Bike LED lamp which I use - it's made by Busch&Muller - German manufacturer and they placed information on the package "90 LUX". But every bike has a different position of front lamp montage bracket, so it's a little difference in distance between lamp and road. That equals different LUXes amount.
Well manufacturers just print numbers on their product specs to make them look more technical and they put a bigger number on the more expensive product and a smaller one on the cheap stuff. Quite often the numbers just don't really mean anything.
at 282 mm radius, the circumference is 1. 77 meter.
it's surface area what is needed, not circumference
Can I use this device to measure solar radiation? Please
The professional lab tool is called an Integrating sphere. It is the Only way to get accurate readings of what is described on the box or from a spec sheet. Lux and lumen are okay if all you need to do is measure visible spectrum rudimentary. Not to mention those testers are veeeery innacurate eveen in testing what they are designed for. Apogee instruments even though they are expensive. Light is serious business.
*How to measure nits of a screen? (cd/m2)*
I dont even know why i like this. But this was dope. And you used the metric system which was refreshing. where you from sir ?
By his accent, England I'd guess
So if you want to measure lumens from sun light how you do it?
Tricky ;)
@@JulianIlett nice video but the information myhbe not correct because lumens is the sommation of all liggt emitted by the bulb you need to redirect all the radiation to your meter sorry for my english .
Dude awesome video!
i need a oscilloscope, I’m wondering if a microphone could be used as a battery to light a led when a noise is detected 🤔😔
you can, basically same way you would connect a light sensor
Area=4⋅π⋅R2 area of a sphere should be in the description.
Julian, PLEASE Do The LED Light Bulb Kit! Build It!!!
6 watts won't get you 800 lumens (60 watts) from an LED, more like 300-400 lumens from an LED, depending on color temp and efficiency.
Typical retail LEDs are around 100 lumens per watt with accurate measurement. The best generally available are around 120. The best kit available on the business market exceeds 200 lumens per watt, focussed on the warehouse lighting market where lighting costs a lot of money.
i hate led lamps, they look extremely bright when directly looking into them but the room is still dark.
I just go with the 125W equivalents, with a good lampshade they look normal but are brighter than a real 100W bub.
You can measure lux using your Android phone if you have auto brightness in your brightness display setting
Just install CPUz and click on sensors tab
Boom
You got another lux measurement device
I found these readings to be extremely inaccurate in most phones.
I have the same meter as Julian and have compared it to the readings of 3 phones some time ago. The *BEST* reading was still around 30% different from the Uni-T.
So to measure a lamp´s brightness, they are useless.
You can measure Lumens. Lux can be calculated by multiplying the measured Lumens by the square area of the projected surface. If it is a light bulb, the surface is a sphere.
Thanks, I made mistakes of what distance it was, thought 1 metre was the distance... oh well, new everyday.
Very nice video
Useful video
You are only looking at about a 2% error or so, that's pretty good
9:38 the best part :D
What's a foot candle 🕯️
Im against using Wikipedia as a source for actual fact. But regardless this has been very illuminating for me cheers
does this device work on candle light 🕯 🤔
Why not?
Wouldn't it be easier with a white pipe?
The white pipe would channel all the light into a much smaller area than 1m²
Your formula for calculating the area of a circle is incorrect.
It should be "A=πr2".
It is not "A=4πr2".
Not sure why I managed to remember a formula from my school days of about 4 decades ago, a formula that I hardly ever need to use, but there you have it.
He very clearly and repeatedly talks about the *sphere* that receives the light, not a circle.
"Area = 4πr²" is the correct formula, for the sphere. He's calculating the radius of a sphere of area 1m².
Briliant! 👍
That was a good explanation. Measuring light intensity is fucked up. Too many units. Also, light meters ( at least cheaper ones
Good trying experiment!
You don't need completely dark room if you can zero the reading, well you can't with this matter :/
the inverse square law of illumination.
thank you
What is FC?
foot candles
This is all so confusing..
I need this
Surely you have one already?
£14 on eBay
Stop saying is not scientific, it really is, although not very precise. :)
Additionally, the assumption under the 28.2cm is that the source of light is a point of size 0, so you should take into account the size of the bulb.
Fork handles Or four candles ? 😂
Foot candles :)
Might hurt the foot, if hot wax got spilled over it... :-D
Kinky! ;)
'andles for forks. Ronnie barker. Hardware shop sketch.
@@simontay4851 👍
9:42 radian in 3D =?
pixel - > voxel
radian - > steradian
2D - > 3D 😎
You can get a PS sphere or a white PVC pipe and accessories and make your own integrating sphere, into which you can put your DUT (in this case the light bulb) and the lux meter, and using a simple calculation you can get the lumens. See this: ruclips.net/video/xOE1ykJ5WAU/видео.html.
Looks like you need a reference source for that method.
retest incand bulb ,, huh
Clarified :)
Don't you have a basement?
No. House built in 1929 - too late for a coal cellar :(
So the conclusion is this meter is useless because you won't get a good condition to measure it😀😀😀
1 JOHN 1:5
This is the message we have heard from Him and announce to you, that *God is Light* ,and in Him there is no darkness at all.
science
BULBS GO IN THE GROUND TO GROW FLOWERS...THAT IS A LAMP
2:24 taking print outs = wasting paper
π×🎥²=💤
Lol