Dude. This is by far the best explainer on focal length that I've seen on TH-cam. I'm a 25-year veteran in the art of photography, but I always like rehashing the basics every now and again. Thanks for this video!! 👍🏾
Best video on focal length on youtube hands down. Concise and to the point and ACTUALLY EXPLAINED what focal length entails and not a dumbed down version that tells you nothing. Thank you. Subbed.
I love it when content such as this gives you "Ohhhhhhhh" moment, connecting multiple concepts together forging an even stronger understanding. Thumbs up for that.
Brief and simple to understand and very informative. It has answered many questions that many other longer videos on TH-cam could not explain. Excellent!!!!!
Agree with many here … never seen a better explanation of this subject, along with the overlays to articulate it soooo well!!! My 8 year old learning photography absolutely adored it! Many thanks!
Bravo! You just answered several longstanding, nagging questions I’ve had about this topic that all the textbooks don’t treat well or ignore entirely. Showing the path of the light and the point of convergence layered on an image of the camera and lens was a brilliant way to communicate this information. Thank you!
came across your channel few days ago. you deserve way more subscribers Dave!.. the way you explain is easy to understand, the graphical overlays are simple but effective. Great content.
very good explanation, I always watch youtube photographers that say they don't want to jump into the math and annoy us till I figured out that they actually don't know anything about it. however, I think any person who call himself a photographer needs a basic understanding of camera electronics and optics, so great job and I am looking forward for more content like this.
Best video on this topic. I have been looking, and no one is as clear and precise with the best examples. Thanks so much for doing this - I was pulling what little hair I have out!! Great job.
this is amazing. I spent soo much time watching many videos, but none of them got straight to the point like this guy. this video is informative and straight to the point. Nice one man....
👍Good time use, not wasted at all. Love the simple but very clear overlay diagrams, along with vid focus changes, and the inversion. A keeper. Don’t recall seeing other vids use your effective overlay technique - instead they cut away to charts, sometimes hand drawn.
I spend a lot of time finding a clear explanation about the focal length until I saw this vid! Loud voice plus clear explanation = great and really helpful video. Approved 😉👍
I went to photography school and that’s basically how it was explained and yet back then we have no idea what a digital camera could do, like none. We did most of our assignments on film and it was explained the same way but using “film” instead of a digital sensor. In fact I got the basic idea in my head that it isn’t what most people think because they’re not technically trained to think that way. Now when I pick up a lens that is either a fixed or a zoom or macro I see this measurement from that converging line of focus and the distance to my sensor being the measurement I’m intending on using.
Great diagrams to explain. I what the focal length was the distance, but didn't think about how that affects the field of view and therefore the size of the lens.
You should mention why Nikon, on there mirrorless cameras, moved the lens closer to the sensor with the larger rear element size. If you use a 50mm Z mount lense it is closer to the sensor than if you use the 50mm F mount lense with the adaptor.
As an optician it was very difficult for me to understand the meaning of focal length in photography and i was really confused But you explained it very well and made me clear Thank you bro Uncle k1❤
Best explanation ever ... point of convergence was deal killer. No body explained like you did. I saw 10 videos and I was all confused but not any more! Thanks!
Very highly informative video on this topic, you clearly explained everything so that an alien would also easily understand !!! Nobodycan perfectly and correctly explain it more than you !! Hat off !!!
hi Dave, thank you so much. so the point of convergence is somewhere within the lens, not on the sensor. That is a very important piece of information. I will check your other videos. thanks again. we need more science about photography.
I didn't learn anything that I didn't already know but still, I thank you for this video because it will help me explain it to my friends at the Photo club. You just made my life easier 👍🏼
Thank you so much for this super clear explanation of focal length. I finally understood it, thanks to you! Brilliant job, thank you for using those lines! 👍😁🙏
Can the point of convergence be outside of the lens? When I measure my nikkor 70-300 @300mm there is at most 230mm from the sensor to the front element
@@DaveMcKeegan Thanks, I would like to know how the lenses produce an equivalent focal length but I think it is very complex. Please add a link to that video in the description.
Awesome video and thanks for making it easy to understand! Perhaps you could even make a part II of the video where you use the same diagrams light ray diagrams to explain the field of view and equivalency of focal lengths on different sensor sizes. You alluded to it early in your video but it would be very clear when you compare for example a 200mm M4/3 lens and a 400mm FF lens with the same field of view but the m4/3 version can be so much smaller due to the focal length being shorter.
Hi.. I have been studying up on this a little bit more and it appears to be you are wrong...it seems like focal length is distance from middle of the lens (incase of camera lenses a virtual point after accounting for every focal length of all the lenses...) to the focal point...(convergence point) (when it is focused to infinity) not the distance to the sensor......The whole reason you'll get a wider DOF on 20mm is because you'll have to mount the lens closer to the sensor to be able to focus the image on to the sensor....otherwise if you leave the 20mm and 200mm lenses mounted at the same place you wouldn't be able to focus the image on to the sensor...I am happy to hear if I am wrong... I see the Nikon USA site is saying what you are saying, but all the articles and videos on physics seems to imply otherwise....You should take another look at this and correct the video if it is wrong....
A "thin lens approximation" for a single piece of lens is measured as the distance from center of the lens to the point of convergence However for photography optical setups which use multiple glass elements, the measurement changes to be from the point of convergence to the sensor
@@DaveMcKeegan Do you have a source where I can do further reading on this? physics books and photography related work uses these 2 definitions 2 different ways and I know there must be a way to explain it to satisfy both descriptions...and many of their ray diagrams are inaccurate....
@@DaveMcKeegan also seems like you are right and wrong www.canon.com.au/explore/glossary/focal-length According to canon it is the distance between optical centre and sensor... not point of convergence....and the optical centre is defined as the point where a light ray passes through any deviation...
@@arunashamal I am going off the various articles from Googling "what is focal length" - a writer on HowToGeek suggests the method of measuring that you pointed out as being the correct way for photography, however every other article (including 2 from Nikon who probably understand this stuff better than most) state its from the point of convergence to the sensor The article on Wiki (not the most reliable I know) states that a single lens is measured from the middle of the glass to the convergence, however for photography it's a measurement from convergence to the sensor
@@DaveMcKeegan Canon and Nikon are screwing with us again with 2 different definitions...smh.. I read the nikon article too how to hell 2 different manufacturers have 2 different definitions?? however if you look at the little diagram on the Nikon article it seems to show the optical centre, because those rays goes through the point of the lens without any deviation... I don't know..
Great video! Thanks for sharing this! I have one question though. In 05:55 you say that in a 200mm micro four thirds lens the point of convergence is 200mm and the angle of view is exactly the same as the full-frame lens. I'm thinking that the only way to achieve this is if the graphic being shown in 05:55 - 06:20 is an oversimplification, because for a smaller sensor with the representation shown, it is clear that the angle of view is smaller than the full-frame sensor. Could it be that the actual setup of the rays inside the lens (after the point of convergence) move differently than the straight lines presented in 05:55? Can anyone confirm or explain?
I measured up my tele zoom, and when zoomed in (250mm) there is 25cm of distance between the sensor and front element at best. Does this mean the point of convergence happens all the way at the front? I just can't imagine a single lens element having such a big impact on the direction of light as it seems quite flat at first sight.
Appreciate the detailed explanation. Could you make video longer by adding how the crop mode is affected effected and works? 4:3 with mirrorless (1.6) vs 16:9 and 3:2.... clear as mud?
Best explanation on this subject ever.
agreed
Agreed!
agreed
disagreed. The explanation is very clear but wrong.
@@Mateo1982able how? Not very helpful to just say he's wrong, tell me how to find out the real answer, by explaining what exactly he got wrong
Dude. This is by far the best explainer on focal length that I've seen on TH-cam. I'm a 25-year veteran in the art of photography, but I always like rehashing the basics every now and again. Thanks for this video!! 👍🏾
Nobody on youtube is as clear as you are in explaining stuff ! Great work !
ya, bro u are so clear. Thank you.
3:49 to 3:53... most clear visual aid ever sir! Thank you, I never understood WHY until this very simple animation.
EXACTLYYYY
Best video on focal length on youtube hands down. Concise and to the point and ACTUALLY EXPLAINED what focal length entails and not a dumbed down version that tells you nothing. Thank you. Subbed.
This is a really good video.
I love it when content such as this gives you "Ohhhhhhhh" moment, connecting multiple concepts together forging an even stronger understanding. Thumbs up for that.
Brief and simple to understand and very informative. It has answered many questions that many other longer videos on TH-cam could not explain. Excellent!!!!!
Explanation and simple graphics made this a total winner. Thank you!!
Simple and straight forward explanation... That is Dave's style.
Agree with many here … never seen a better explanation of this subject, along with the overlays to articulate it soooo well!!! My 8 year old learning photography absolutely adored it!
Many thanks!
Thank you for taking the time to put the graphics on your hand movements during your excellent explanation. Tip top
I have watched literally dozens of videos on focal length trying to get my head around it and this is hands down the best explaination.
Best explanation on TH-cam. Thank you mate.
Bravo! You just answered several longstanding, nagging questions I’ve had about this topic that all the textbooks don’t treat well or ignore entirely. Showing the path of the light and the point of convergence layered on an image of the camera and lens was a brilliant way to communicate this information. Thank you!
Very insightful. I learned something about focal length that I didn’t know before.
This reminded me of the same topic back in my third grade in my high school. now i can connect the dots. thanks man.
came across your channel few days ago. you deserve way more subscribers Dave!.. the way you explain is easy to understand, the graphical overlays are simple but effective.
Great content.
Nobody explains this topic so great as you did. Great job!
This video will never get old. Thank you. Clear and concise.
very good explanation, I always watch youtube photographers that say they don't want to jump into the math and annoy us till I figured out that they actually don't know anything about it. however, I think any person who call himself a photographer needs a basic understanding of camera electronics and optics, so great job and I am looking forward for more content like this.
Thanks Nader, I already have a few other videos similar to this on my channel but no doubt there will be even more in the future 😊
I am photographer for nearly 10 years...I never thought about this...This makes totally sense suddenly!Thank you very much for the lesson !
Dude this explanation was PHENOMENAL
Best video on this topic. I have been looking, and no one is as clear and precise with the best examples. Thanks so much for doing this - I was pulling what little hair I have out!! Great job.
Finally, someone who doesn't just say "the higher the number, the more zoomed in it is"
Awesome video!
this is the best explanation on youtube
Bro you deserve the Nobel Peace prize for this explanation and break down of this SM!
Absolutely fantastic. Before I clicked the video, I really was not expecting to learn so much, geez.
Thanks, glad you enjoyed it ☺️
Thanks so much for the explanation! I was meaning to look this up sometime, and your video just came up. Great explanation!
this is amazing.
I spent soo much time watching many videos, but none of them got straight to the point like this guy.
this video is informative and straight to the point.
Nice one man....
👍Good time use, not wasted at all. Love the simple but very clear overlay diagrams, along with vid focus changes, and the inversion. A keeper. Don’t recall seeing other vids use your effective overlay technique - instead they cut away to charts, sometimes hand drawn.
Am I the only one AMAZED by his motion tracking !!?
Thanks!
I spend a lot of time finding a clear explanation about the focal length until I saw this vid! Loud voice plus clear explanation = great and really helpful video. Approved 😉👍
I went to photography school and that’s basically how it was explained and yet back then we have no idea what a digital camera could do, like none. We did most of our assignments on film and it was explained the same way but using “film” instead of a digital sensor. In fact I got the basic idea in my head that it isn’t what most people think because they’re not technically trained to think that way. Now when I pick up a lens that is either a fixed or a zoom or macro I see this measurement from that converging line of focus and the distance to my sensor being the measurement I’m intending on using.
Excellent video Dave, im in for version two of this :)..keep em coming. Huge Thanks!
Haha, that maybe something for the future 😊
AWESOME.....great work and masterfully explained ! 👍
Others have commented this already, but this explanation is the best I've seen, I finally understand focal length.
Самое лучшее объяснение темы, из тех которые я встречал на просторах сети. Спасибо!
Great diagrams to explain. I what the focal length was the distance, but didn't think about how that affects the field of view and therefore the size of the lens.
Brilliant best and easiest to understand video on focal length I've ever seen.
Glad it was helpful!
Jesús never heard a clearer explanation for this topic cheers mate!
Excellent, I searched and now I found your simple explanation of what mm measurements on a lens means. Big thank you.
Simple, easy and best explanation. Great job dude
You should mention why Nikon, on there mirrorless cameras, moved the lens closer to the sensor with the larger rear element size. If you use a 50mm Z mount lense it is closer to the sensor than if you use the 50mm F mount lense with the adaptor.
Thank you for not dumbing it down. Trying to make the explanation "simple" to often only makes it confusing.
Nice explanation!! Cleared my Focal length and lens size doubts!!
Finally someone who has explained this perfectly - thankyou!
As an optician it was very difficult for me to understand the meaning of focal length in photography and i was really confused
But you explained it very well and made me clear
Thank you bro
Uncle k1❤
Thank you for the explanation! I watched a few other videos and couldn't completely make sense of it until yours. Great job!
Best explanation ever ... point of convergence was deal killer. No body explained like you did. I saw 10 videos and I was all confused but not any more! Thanks!
Super great video with fantastic explanation, even a beginner will fully understand this
best illustration about this topic so far! thanks!
You're welcome 😊
Excellent explanation in regards to focal length distance, angle of view, aps-c vs full frame sensor, and physical size/length of lens.
Very highly informative video on this topic, you clearly explained everything so that an alien would also easily understand !!! Nobodycan perfectly and correctly explain it more than you !! Hat off !!!
I agree with other comments , the best video explanation on this subject.
Well done Dave
Man, super content: clear and compact !
A very fine refresher...Thank You Dave...
the brain does not compensate anything. we live hanging from the ground.
That was the best video on focal length I have ever seen. Thanks so much, I learned a lot.
THANK YOU!! Best explanation on the internet
I am so learning from a true master - thank you! 😎👍
I suspect we all are - ouch ;)
Excellent my man! Been racking my brain. Thank you
finally i learned the science behind focal length, thank you very much sir
The only channel (I’ve seen) to actually say what focal length is.
Excelllent, clear and concise tutorial. Brilliant!
Glad it was helpful Peter
hi Dave, thank you so much. so the point of convergence is somewhere within the lens, not on the sensor. That is a very important piece of information. I will check your other videos. thanks again. we need more science about photography.
Great video
An excellent explanation. Clear and to the point.
Great video. You cleared up some misconceptions that I had. Subbed. Thx!
OMG, your diagram is off the charts! Thank you!
As simple as it could get. Keep it goin'
An excellent explanation of focal length, exactly what I came here for, thanks 👌
Simple topic, explained simply. Perfect!
This is the best one on this subject I have ever seen
Thanks 😊
Fantastic video. Well put together
Small point: the image is not upside down, but rotated 180 degrees. Up is down AND left is right.
or flipped in both the horizontal and vertical plane. The same effect as rotation, accept rotation implies a motion that doesn't occur.
It is upside down then. ;)
David Marquez yes and left side right, which was the point of the comment...
Edward Noble to be precise an inversion occurs, not a double flip, that implies flips that do not occur...
"Up is down" that is the meaning of upside down
I didn't learn anything that I didn't already know but still, I thank you for this video because it will help me explain it to my friends at the Photo club.
You just made my life easier 👍🏼
Best explanation I've heard. Great video!
Best explanation by far! 👌🏻🔥
Used today's 10 min usefully ❤️
Love from India ❤️
Absolutely cracking explanation! Thank you
Thank you so much for this super clear explanation of focal length. I finally understood it, thanks to you! Brilliant job, thank you for using those lines! 👍😁🙏
Thank you! Finally a good explanation on this topic!
Can the point of convergence be outside of the lens? When I measure my nikkor 70-300 @300mm there is at most 230mm from the sensor to the front element
This more recent video I've made should answer that for you
th-cam.com/video/ndnzekp6HMk/w-d-xo.html
@@DaveMcKeegan Thanks, I would like to know how the lenses produce an equivalent focal length but I think it is very complex. Please add a link to that video in the description.
THANK YOU SIR
Awesome video and thanks for making it easy to understand! Perhaps you could even make a part II of the video where you use the same diagrams light ray diagrams to explain the field of view and equivalency of focal lengths on different sensor sizes. You alluded to it early in your video but it would be very clear when you compare for example a 200mm M4/3 lens and a 400mm FF lens with the same field of view but the m4/3 version can be so much smaller due to the focal length being shorter.
Hi.. I have been studying up on this a little bit more and it appears to be you are wrong...it seems like focal length is distance from middle of the lens (incase of camera lenses a virtual point after accounting for every focal length of all the lenses...) to the focal point...(convergence point) (when it is focused to infinity) not the distance to the sensor......The whole reason you'll get a wider DOF on 20mm is because you'll have to mount the lens closer to the sensor to be able to focus the image on to the sensor....otherwise if you leave the 20mm and 200mm lenses mounted at the same place you wouldn't be able to focus the image on to the sensor...I am happy to hear if I am wrong... I see the Nikon USA site is saying what you are saying, but all the articles and videos on physics seems to imply otherwise....You should take another look at this and correct the video if it is wrong....
A "thin lens approximation" for a single piece of lens is measured as the distance from center of the lens to the point of convergence
However for photography optical setups which use multiple glass elements, the measurement changes to be from the point of convergence to the sensor
@@DaveMcKeegan Do you have a source where I can do further reading on this? physics books and photography related work uses these 2 definitions 2 different ways and I know there must be a way to explain it to satisfy both descriptions...and many of their ray diagrams are inaccurate....
@@DaveMcKeegan also seems like you are right and wrong www.canon.com.au/explore/glossary/focal-length
According to canon it is the distance between optical centre and sensor... not point of convergence....and the optical centre is defined as the point where a light ray passes through any deviation...
@@arunashamal I am going off the various articles from Googling "what is focal length" - a writer on HowToGeek suggests the method of measuring that you pointed out as being the correct way for photography, however every other article (including 2 from Nikon who probably understand this stuff better than most) state its from the point of convergence to the sensor
The article on Wiki (not the most reliable I know) states that a single lens is measured from the middle of the glass to the convergence, however for photography it's a measurement from convergence to the sensor
@@DaveMcKeegan Canon and Nikon are screwing with us again with 2 different definitions...smh.. I read the nikon article too how to hell 2 different manufacturers have 2 different definitions?? however if you look at the little diagram on the Nikon article it seems to show the optical centre, because those rays goes through the point of the lens without any deviation... I don't know..
Now I understand what is focal length. Thanks.
Brilliant! Good work man!
Great video! Thanks for sharing this!
I have one question though. In 05:55 you say that in a 200mm micro four thirds lens the point of convergence is 200mm and the angle of view is exactly the same as the full-frame lens. I'm thinking that the only way to achieve this is if the graphic being shown in 05:55 - 06:20 is an oversimplification, because for a smaller sensor with the representation shown, it is clear that the angle of view is smaller than the full-frame sensor. Could it be that the actual setup of the rays inside the lens (after the point of convergence) move differently than the straight lines presented in 05:55? Can anyone confirm or explain?
I measured up my tele zoom, and when zoomed in (250mm) there is 25cm of distance between the sensor and front element at best. Does this mean the point of convergence happens all the way at the front? I just can't imagine a single lens element having such a big impact on the direction of light as it seems quite flat at first sight.
May I ask what the lens is you were measuring
Perfectly explained
Amazed by the explanation!!
This video is absolutely insane. I have learned so much.
Appreciate the detailed explanation. Could you make video longer by adding how the crop mode is affected effected and works? 4:3 with mirrorless (1.6) vs 16:9 and 3:2.... clear as mud?
Amazing explanation! Thank you for the animations.
Absolutely crystal clear with nano coating 😃
You explain very well mate, well done! Love it!
Best by far explanation on this subject....thank you ..
Thank you Jim :)