"What is Focal Length?" - The science behind it explained.

[@grat2010]

Best explanation on this subject ever.

[@photography5607]

agreed

[@aarin911]

Agreed!

[@marvinracer88]

agreed

[@Mateo1982able]

disagreed. The explanation is very clear but wrong.

[@tophmyster]

​@@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

[@deeplybrown]

Dude. This is by far the best explainer on focal length that I've seen on KZbin. 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!! 👍🏾

[@PaoloMassa74]

Nobody on youtube is as clear as you are in explaining stuff ! Great work !

[@enoluca6095]

ya, bro u are so clear. Thank you.

[@Ben-mx1ip]

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.

[@jamiewindsor]

This is a really good video.

[@johnbarry5036]

3:49 to 3:53... most clear visual aid ever sir! Thank you, I never understood WHY until this very simple animation.

[@JeffreywixYouTube]

EXACTLYYYY

[@devinharris9284]

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.

[@richardslider4070]

Very insightful. I learned something about focal length that I didn’t know before.

[@igorgoga7985]

this is the best explanation on youtube

[@freshoxygen2176]

Explanation and simple graphics made this a total winner. Thank you!!

[@Govinnu]

Simple and straight forward explanation... That is Dave's style.

[@jamesscott1813]

Thank you for taking the time to put the graphics on your hand movements during your excellent explanation. Tip top

[@gserghiou]

Brief and simple to understand and very informative. It has answered many questions that many other longer videos on KZbin could not explain. Excellent!!!!!

[@tirthankardatta2493]

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!

[@matrixate]

Best explanation on KZbin. Thank you mate.

[@kennethshermock8512]

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!

[@tharinduwijayasena309]

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.

[@petrvala9955]

Nobody explains this topic so great as you did. Great job!

[@JoeChira]

This reminded me of the same topic back in my third grade in my high school. now i can connect the dots. thanks man.

[@SShaBazzz]

Great video

[@AlexandarHullRichter]

Thanks so much for the explanation! I was meaning to look this up sometime, and your video just came up. Great explanation!

[@ianezy0828]

This video will never get old. Thank you. Clear and concise.

[@andrewriley4990]

AWESOME.....great work and masterfully explained ! 👍

[@accessmountain2019]

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.

[@GooseCee]

Dude this explanation was PHENOMENAL

[@byronjohnson8346]

THANK YOU SIR

[@iu1191]

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.

[@paulm8157]

👍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.

[@jondemetrius]

Bro you deserve the Nobel Peace prize for this explanation and break down of this SM!

[@nadergadelrab2669]

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.

[@DaveMcKeegan]

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 😊

[@thisisnonpractice]

Nice explanation!! Cleared my Focal length and lens size doubts!!

[@floridian2023]

Thanks!

[@atif.hassan]

Excellent video Dave, im in for version two of this :)..keep em coming. Huge Thanks!

[@DaveMcKeegan]

Haha, that maybe something for the future 😊

[@sludgepuppy]

Absolutely fantastic. Before I clicked the video, I really was not expecting to learn so much, geez.

[@DaveMcKeegan]

Thanks, glad you enjoyed it ☺️

[@alwashburn3098]

A very fine refresher...Thank You Dave...

[@solracthegreat1002]

Jesús never heard a clearer explanation for this topic cheers mate!

[@jhay_vine5083]

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....

[@Mart77]

Super great video with fantastic explanation, even a beginner will fully understand this

[@codypieper728]

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.

[@pradeeshsimon]

Simple, easy and best explanation. Great job dude

[@duckbizniz663]

Excellent explanation in regards to focal length distance, angle of view, aps-c vs full frame sensor, and physical size/length of lens.

[@mrfairycake4333]

Brilliant best and easiest to understand video on focal length I've ever seen.

[@DaveMcKeegan]

Glad it was helpful!

[@MeanTheBean]

best illustration about this topic so far! thanks!

[@DaveMcKeegan]

You're welcome 😊

[@jpcalamaro961]

An excellent explanation. Clear and to the point.

[@billzidis2656]

I am photographer for nearly 10 years...I never thought about this...This makes totally sense suddenly!Thank you very much for the lesson !

[@Jhet]

Finally, someone who doesn't just say "the higher the number, the more zoomed in it is" Awesome video!

[@bennails3447]

Самое лучшее объяснение темы, из тех которые я встречал на просторах сети. Спасибо!

[@konstantinosoikonomou5297]

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?

[@purohitarvind]

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!

[@mymagicmurals]

Excellent, I searched and now I found your simple explanation of what mm measurements on a lens means. Big thank you.

[@hombrelobomedia3503]

Excellent my man! Been racking my brain. Thank you

[@vanessajacques7293]

Thank you for the explanation! I watched a few other videos and couldn't completely make sense of it until yours. Great job!

[@blackmo_or]

Absolutely cracking explanation! Thank you

[@peterbarriscale7857]

Excelllent, clear and concise tutorial. Brilliant!

[@DaveMcKeegan]

Glad it was helpful Peter

[@lenmc9652]

Fantastic video. Well put together

[@embraceme330]

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 😉👍

[@pk6221]

Man, super content: clear and compact !

[@MetallaCaine]

That was the best video on focal length I have ever seen. Thanks so much, I learned a lot.

[@jhay_vine5083]

Am I the only one AMAZED by his motion tracking !!?

[@EishahArmaghan]

Amazed by the explanation!!

[@jamesbaxter9123]

Finally someone who has explained this perfectly - thankyou!

[@fpranchas]

THANK YOU!! Best explanation on the internet

[@JK-jl1bf]

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.

[@Twobarpsi]

Best explanation I've heard. Great video!

[@tomelifeisjustonebig]

Simple topic, explained simply. Perfect!

[@Professorjoeyy]

Thank you! Finally a good explanation on this topic!

[@MelvinSabu]

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 !!!

[@EternalAwait]

Others have commented this already, but this explanation is the best I've seen, I finally understand focal length.

[@smokeebeefpv]

Great video. You cleared up some misconceptions that I had. Subbed. Thx!

[@jamesurzykowski4918]

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.

[@time589]

Thank you for not dumbing it down. Trying to make the explanation "simple" to often only makes it confusing.

[@Dylan-ox5fb]

Great video with a simple explanation!

[@shibbyjay123]

An excellent explanation of focal length, exactly what I came here for, thanks 👌

[@Badshaah26]

As simple as it could get. Keep it goin'

[@曹宇-t7k]

Thanks man! Clearest explanation!

[@arifkizilay]

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.

[@EricaRodriguez12]

OMG, your diagram is off the charts! Thank you!

[@NaqeebAl]

Brilliant! Good work man!

[@tysonator5433]

I agree with other comments , the best video explanation on this subject. Well done Dave

[@jimpan8471]

Best by far explanation on this subject....thank you ..

[@DaveMcKeegan]

Thank you Jim :)

[@adolloyd]

I am so learning from a true master - thank you! 😎👍

[@beachbum4691]

I suspect we all are - ouch ;)

[@jhay_vine5083]

THIS VIDEO IS AMAZING! THANK YOU SIR!

[@albinpremvelayil]

Best explanation by far! 👌🏻🔥

[@belal29customs]

This is the best one on this subject I have ever seen

[@DaveMcKeegan]

Thanks 😊

[@lukozi01]

Excellent video! Very well explained!

[@davidhrzenjak]

finally i learned the science behind focal length, thank you very much sir

[@fredlevel897]

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 👍🏼

[@Pondstreeter]

Truly a great explanation.

[@elenagoswell3649]

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! 👍😁🙏

[@goos4711]

Thanks. This makes so much sense.

[@helpfixstupid6190]

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?

[@martinlawrence8427]

Superbly clear and useful explanation. Thanks!

[@theJaseEdwards]

Holy crap, you just made all the sense in the world. Thank you!

[@geraldflores6895]

Amazing bro looking for the right awnser and theory and you video was the awenser thanks so much well done explaned

[@frankzhao8352]

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.

[@yoshikobailung1474]

Really clear explanation. Thank you.

[@dreamingguy1999]

This is Amazing Explanation.

[@ainzizou]

You explain very well mate, well done! Love it!

[@veeds74123]

Amazing explanation! Thank you for the animations.

[@johnvarghese8742]

So helpful tips. Thank you Dave:)