Skip to main content

Focal Length Rule of Thumb

Lesson 7 from: Canon Lenses: The Complete Guide

John Greengo

Focal Length Rule of Thumb

Lesson 7 from: Canon Lenses: The Complete Guide

John Greengo

buy this class


Sale Ends Soon!

starting under


Unlock this classplus 2200+ more >

Lesson Info

7. Focal Length Rule of Thumb

Next Lesson: Field of View


Class Trailer

Class Introduction


Canon Lens Basics


Focal Length: Angle of View


Focal Length: Normal Lenses


Focal Length: Wide Angle Lenses


Focal Length: Telephoto Lens


Focal Length Rule of Thumb


Field of View


Aperture Basics


Aperture: Maximum Aperture


Aperture: Equivalent Focal Length


Aperture: Depth of Field


Aperture: Maximum Sharpness


Aperture: Starburst Effect


Aperture: Flare


Aperture: Hyperfocal Distance


Camera Mount System


Canon Lens Compatibility


Canon Lens Design


Canon Lens Composition


Canon Lens Shape


Canon Lens Coating


Canon Lens Focusing


Lens Autofocus


Canon Lens Image Stabilization


Canon L Lenses


Image Quality


Canon Zoom Lenses: Standard


Canon Super Zooms


Canon Wide Zooms


Canon Telephoto Zooms


Prime Lens: Normal Lenses


Prime Lens: Moderate Wide


Prime Lens: Wide Angle


Prime Lens: Ultra-Wide


Prime Lens: Short Telephoto


Prime Lens: Medium Telephoto


Prime Lens: Super Telephoto


3rd Party Lenses Overview


3rd Party Prime Lenses


3rd Party Zoom Lenses


Lens Accessories: Filters


Lens Accessories: Lens Hoods


Lens Accessories: Tripod Mount


Lens Accessories: Extension Tubes


Lens Accessories: Extenders


Macro Lens: Reproduction Ratio


Macro Lens: Technique and Choices


Fisheye: Technique and Choices


Tilt Shift: Techniques and Choices


Make a Lens System Choice


Choosing A Portrait Lens


Choosing A Sports Lens


Choosing A Landscape Lens


Best Lenses for You


Lens Maintenance


Buying and Selling Lens


What is John Greengo's Favorite Lens?


Lesson Info

Focal Length Rule of Thumb

Let's do the rule of thumb. All right, it's, a little bit of participation time here in the classroom. So in case you don't have your camera with you and you're out scouting and it's time for you to well, I want to come back here at sunset, but I'm not sure what lens I need so fifty millimeter is what I call movie hands on. So movie hands is if you go ahead, put your hands up like this and you don't want to have your thumbs together. It depends. Maybe four, six inches between your thumbs, something like that bend your elbow so not all the way out. Just nice, kind of comfortable here and close one eye and just kind of pan around the room and that's about what you see with a fifty millimeter lens. And so let me let me test myself. I got to have my have a fifty over here. So with a fifty millimeter lens, I'm going to try to get a three shot here. Three of you in one shot, I think. Let's. See, I think I need to be right here. Okay, so right there now, let's. See? Let's say so too, right? W...

ho I'm close right here so I thought I was here but I'm actually right here and so that's a fifty millimeter lands okay so if you ever want to know what a fifty is just comfortable on the elbows thumbs four to six inches apart and right there so that's our movie hands now you want to know what a thirty five is I haven't come up with anything creative here it's just a little bit wider so just throw another three inches in behind there and so a slightly so I could probably get a four shot of you guys out here with with a thirty five millimeter lance all right so we're gonna have to get a little more creative now all right so let's do the twenty four millimeter lads and this one's kind of unusual so if you grab your elbows right here grab your elbows like this and let's get your thumbs up like this because I want your thumbs right above your elbows right here and what you see above your close one eye and what you see between your thumbs is pretty close to what you're going to see with the twenty four so I could get all five of you with the twenty four millimeter lands all right, let's see how good I am so no three I protect that I need to be right here with a twenty four millimeter let's. Okay? Can you guys remember the spot I'm going to switch over to a twenty four millimeter lands let's. See, do I have a twenty four millimeter lands? How easy is this? This is exactly how I keep lenses at my house, all labeled right out on the shelf. Okay, so I was getting all of you in one shot, and so I need to be right. Hear how close to mine really close. Okay, so that's. A twenty four millimeter lands. All right and let's go to the next one sixteen millimeter lands if you just close one eye and okay kind of ignored like the way ofthe stuff but kind of what you see with one eye that's going to be about a sixteen millimeter lands you get a kind of ignore this stuff way way off because you can actually see pretty far with one eye but kind of like okay I like everything right there that's a sixteen millimeter last now if you want to know what one hundred millimeter thumb his okay you know this will do theyjust in hawaii high five or something I don't but if you hold this out like this and you hold it out at arm's length the distance between your thumb and your pinky is about one hundred millimeter lands and so I can tell I could do like a two of you right about here with one hundred millimeter lance so what am I going to see from side to side with one hundred millimeter lands all right and this is probably my favorite one this is it everybody put your finger out like this like you want a little bird to land on your arm and you got to keep your arms straight all the way out the distance between your fingers is what you're going to see with the two hundred millimeter lands and so there's a creative live loge away on the back wall and I think that I would be a two hundred millimeter lens right here to shoot with and says sometimes handing before you start pulling out equipment how big is that and so you know if I'm I'm doing these gestures you know it's it's not gang signs or anything hi four hundred millimeters arm's length okay so ok so I could do a tight head shot on one of you with a four hundred millimeter lens from here what do I see in there with that and if you want to know what you're going to see within eight hundred millimeter lands it's whatever you can obliterate with your thumb so if you get your thumb all the way out now the thing that I don't know is that different people have different sized body parts at least that's what I hear and I'm thinking that if you have a really big thumb you probably have a pretty big long arm and if you have a small arm you probably have a smaller thumb and so it's it's probably going to come pretty close to this and so this is all rule of thumb and so it's you know it's not exact science but it's close enough to get you pretty close do a test yourself you know what does this look like with the fifty put on your fifty and see where that puts you yourself so that's just kind of a fun way to think about these when you don't have your camera with you all right so we talked about our normal and are wide angle lenses and just something I want to know is that as you get to these wider angle lenses they become more difficult to build which means they cost more money and they're also more difficult to use as we go from fifty and we go into the telephoto range they become more difficult to build they become more costly they become bigger in size and they've become more difficult to use if I was designing the john gringo university of photography here is probably the way it would work welcome to the university you are a freshman you will be issued a fifty millimeter lands for your first semester that is all you get to use at the end of your semester if you pass all your classes you will be issued a thirty five and a hundred millimeter lands and you'll continue to use that throughout your first year of photography as a sophomore you will then get a twenty four and two hundred and then after that you move up to junior where you get to go to sixteen to four hundred and then in your senior year you'd be able to work on special projects with the eleven in the eight hundred millimeter lands on one of the problems that I see is photographers who are new to photography but they have a really big budget doesn't happen a lot but every once in a while somebody's got a big budget they want to get into it and they go like straight up to a four hundred millimeter lands and this is like giving a lamborghini to a sixteen year old I'm going to place a bet that thing is going to be in the shop in two weeks you know it's just too much horsepower and so slowly working your way out from the center is what I would recommend if you want a great learning experience just go out with fifty millimeter lands that's going to force you to look at things in different ways you could say that of any different lands just choose that one lens and shoot with it but the fifty is going to make you work hard and it's really going to make you appreciate other things as you start moving from there so I have been shooting for this class and I wanted to shoot a lot of photos that showed everything from eleven to eight hundred so I've been carrying around a three large camera bag off lenses so that I could shoot a variety examples just to help ingrain ing you what you are going to see with different lenses is so here in seattle at the university of washington is this called rainier avenue or rainier vista right in the middle of the university of washington so here we have our normal fifty millimeter lands let's go out wide to thirty five and we can see our steps that lead down to the water fountain in the distance all the way down to at eleven millimeter lands now are eleven millimeter lens will talk more about this another section is a rectilinear lens which means straight lines are rendered straight there is a lot of distortion in here but look at the stairs do these stairs look normal they are straight lines they have not changed if they were round like a soccer ball they would change but they're straight lines and they're not changing but if you look at the steepness of the angles especially 00:08:01.875 --> 00:08:04. way off here on the left hand his eye that's caused 00:08:04.91 --> 00:08:08. by the eleven millimeter lands distortion all right 00:08:08.4 --> 00:08:11. so that's eleven millimeters let's bring it up back 00:08:11.12 --> 00:08:11. to normal 00:08:13.04 --> 00:08:15. fifty and now this is very much what it looks like 00:08:15.67 --> 00:08:18. standing on the top of those stairs let's go into 00:08:18.64 --> 00:08:21. our hundred two hundred now we're getting a good look 00:08:21.47 --> 00:08:25. at mount rainier which is seventy miles from seattle 00:08:26.54 --> 00:08:29. so at seventy miles in the distance and let's bring 00:08:29.06 --> 00:08:33. it back down to fifty millimeters and so that's one 00:08:33.04 --> 00:08:35. series and I kind of got hooked I was trying to think 00:08:35.47 --> 00:08:38. of his many different places I could go shoot a full 00:08:38.57 --> 00:08:42. siri's from eleven to eight hundred so downtown on 00:08:42.55 --> 00:08:45. I believe this is fourth avenue our fifty millimeter 00:08:45.99 --> 00:08:48. lands let's go back all the way to eleven 00:08:50.44 --> 00:08:53. and we'll be able to see the entire gigantic piece 00:08:53.19 --> 00:08:56. of artwork in front of us, as well as the whole building 00:08:56.37 --> 00:08:59. and the sidewalk that I'm on let's. Zoom into eight 00:08:59.44 --> 00:09:01. hundred and see what we can see. Some construction project down there, and we'll bring it back down to fifty. So I took these down to the southwest with me, and I wanted to shoot this in a variety of areas. And so this was photo we saw earlier in the eleven millimeter section, but what would it look like with a different lens? Well, let's. Bring it out and zoom out to sixteen and there's. Many photographers who would prefer to shoot in here with a twenty four millimeter lands because the background doesn't seem quite a small and far away and just gives you a hint of the foreground. In some cases, you want to see everything in the foreground. In some cases you just want to hit. It depends on the style of photograph that you want. Both are valid choices, depending on what you the artist wants out of your photographs. So once we get into fifty, we start forgetting about the foreground, because it's, too narrow of a view, and we'll go all the way in to eight hundred. 00:10:04.26 --> 00:10:07. And so the better that you can pre visualize what 00:10:07.25 --> 00:10:09. lens you need and what it's going to look like and 00:10:09.96 --> 00:10:12. what you want out of a photograph is going to improve 00:10:12.73 --> 00:10:14. your photography because then you'll know how to set 00:10:14.51 --> 00:10:17. up where to say tripod up where to move what lens 00:10:17.24 --> 00:10:18. is going to work in different situations 00:10:20.46 --> 00:10:22. so in this case I'm actually going to employ a fisheye 00:10:22.74 --> 00:10:24. which we're gonna have a whole special section on 00:10:24.46 --> 00:10:26. later which kind of curves the horizon and there's 00:10:26.63 --> 00:10:30. a lot of very purposeful distortion in these and this 00:10:30.33 --> 00:10:33. is angels landing in zion national park it's a beautiful 00:10:33.86 --> 00:10:38. fun hike very exposed wall that you are in the very 00:10:38.13 --> 00:10:41. top of and there's some great little lookouts and 00:10:41.04 --> 00:10:46. so I set up here can I zoomed in hand I found something 00:10:46.19 --> 00:10:48. kind of interesting to see if you notice it you see 00:10:48.76 --> 00:10:50. it yet fifty kind of hard to see because it's pretty 00:10:50.99 --> 00:10:52. small it zoom in a little closer 00:10:53.66 --> 00:10:54. maybe you can start to see it here 00:10:56.16 --> 00:10:59. there is a group of rock climbers right up there halfway 00:10:59.5 --> 00:11:02. up the wall I think they had just pulled their tent 00:11:02.66 --> 00:11:05. down they slept the night on the wall there and so 00:11:05.38 --> 00:11:08. let's bring it back to a normal fifty millimeter lands 00:11:08.96 --> 00:11:10. actually let's go back all the way to the fish islands 00:11:12.46 --> 00:11:13. and so 00:11:14.1 --> 00:11:16. I think it's just kind of a fun siri's to see what 00:11:16.84 --> 00:11:18. you see with these different lenses now the main reason 00:11:18.94 --> 00:11:21. I was up there as I was trying to shoot the other 00:11:21.05 --> 00:11:25. direction off of the peak they're up they're down 00:11:25.52 --> 00:11:29. zion valley and I was trying to find something kind 00:11:29.03 --> 00:11:32. of interesting to photograph in particular with long 00:11:32.28 --> 00:11:33. lens because I want to have something that we were 00:11:33.86 --> 00:11:37. going to and there wasn't much but I did find a beautiful 00:11:37.63 --> 00:11:42. tree right in the middle of these ion lodge launch 00:11:43.36 --> 00:11:46. and so I shot this siri's and I thought you know I'd 00:11:46.81 --> 00:11:50. be kind of cool is if I hiked down and I went right 00:11:50.47 --> 00:11:52. down to the tree see these people right in front of 00:11:52.04 --> 00:11:55. the tree and I got right down there and I pointed 00:11:55.51 --> 00:11:58. the camera exactly where I was taking the photo and 00:11:58.77 --> 00:12:01. so I took my lenses I went down there and I was right 00:12:01.95 --> 00:12:03. up here on the speaking can see all these people that 00:12:03.76 --> 00:12:05. climb mother the summertime it's very crowded up there 00:12:06.28 --> 00:12:08. and so that was at eight hundred and let's go backto 00:12:08.93 --> 00:12:11. wide angle and you can see angels landing the peak 00:12:11.75 --> 00:12:12. that I climbed up 00:12:13.78 --> 00:12:15. and you can see the people who are still down there 00:12:15.84 --> 00:12:17. there's still hanging out in the yard all the way 00:12:17.81 --> 00:12:20. down to the fish eye which is actually starting to 00:12:20.75 --> 00:12:23. see the branches of the tree that we saw in the earlier 00:12:23.55 --> 00:12:27. photograph and so just I don't know how educational 00:12:27.33 --> 00:12:30. is's but visually it makes me think about focal links 00:12:31.2 --> 00:12:34. and I'm hoping that it helps you I haven't identified 00:12:34.04 --> 00:12:37. exactly what it improves in your photography but I 00:12:37.21 --> 00:12:39. think it's kind of fun and I plan to do more of this 00:12:39.2 --> 00:12:41. in the future now this is a special siri's this is 00:12:41.91 --> 00:12:43. a different siri's because in all the other siri's 00:12:43.99 --> 00:12:47. what I was doing is I was just setting up my tripod 00:12:47.41 --> 00:12:49. and changing lenses and it's pretty easy to do that 00:12:50.28 --> 00:12:53. this is a diff more difficult siri's because jin is 00:12:53.32 --> 00:12:55. sitting in the same spot but I'm going to be switching 00:12:55.76 --> 00:12:58. lenses and I'm going to be losing closer and further 00:12:58.6 --> 00:13:01. away from her so that she remains exactly the same 00:13:01.8 --> 00:13:05. size in the frame so this is our fifty millimeter 00:13:05.0 --> 00:13:07. lands very normal perspective this is very much the 00:13:07.91 --> 00:13:11. what we would identify as normal lucky now as we go 00:13:11.55 --> 00:13:14. wider angle what are we doing we're going to get more 00:13:14.65 --> 00:13:17. distortion and in this case her legs were kind of 00:13:17.93 --> 00:13:19. looking bigger and her head's looking a little bit 00:13:19.54 --> 00:13:22. smaller because her legs are closer to us and we go 00:13:22.44 --> 00:13:25. all the way down to the fish eye a little bit of distortion 00:13:25.49 --> 00:13:27. here now fish eye one of the things we'll talk more 00:13:27.89 --> 00:13:31. about in the specialty lend section is the fist fisheye 00:13:31.33 --> 00:13:34. distorts things but if a straight line in this case 00:13:34.32 --> 00:13:37. the horizon runs through the middle of the frame, 00:13:37.18 --> 00:13:39. straight lines will be still rendered straight 00:13:40.62 --> 00:13:42. straight excuse me straight lines to the middle of 00:13:42.45 --> 00:13:45. the frame will be straight so let's go back to our 00:13:45.29 --> 00:13:49. normal wide angle sixteen in twenty four and as we 00:13:49.66 --> 00:13:52. go up back to fifty we're going to start getting into 00:13:52.1 --> 00:13:54. our telephoto effect and I'm moving the camera further 00:13:54.7 --> 00:13:58. away from her and notice what happens to the background 00:13:58.14 --> 00:14:01. as we go from fifty to one hundred and two hundred 00:14:01.58 --> 00:14:04. and earlier I said that by using a telephoto lens hands it reduces the size of the background area so what's behind her will we have the entire steps? Well now we only have a portion of the steps and at eight hundred we have a very small portion of those steps and so in this case when I was photographing her eye was about fifty yards away from her at the time so if I'm fifty yards away at eight hundred I'm probably about twenty five yards of four hundred and about twelve and a half yards here and so when I took these photos it was kind of interesting because I was marking tape on the sidewalk where I wass and it was like I was shot I shot the fifteen here and the sixteen here and the twenty four here and the thirty five here in each one incrementally doubled in distance until I was having almost use a walkie talkie on the last one toe tell when I was taking the photograph there and so it kind of an interesting. This is known as a hitchcock zoom or a dolly zoom and it's, a it's. An interesting way of shooting. And there is going to be another siri's of this with tan in a different way, using the same technique. But we're going to be doing a head shot when we go into the portrait section about what lenses c for tight headshots. And what is the best lands and what's the effect of using either a longer or shorter focal. Like so. Expect a lot more information on portrait lenses as we go forward. Because I got lots of different ones to share with you there.

Class Materials

Bonus Materials with Purchase

What's in the Frame? HD
What's in the Frame? LOW
Field of View HD
Field of View LOW
Lens Keynote Parts 1-4
Lens Keynote Parts 5-8
Canon® Lens Data

Ratings and Reviews


I so appreciate what a good teacher John is. I wish I would have known this much about lenses when I first started out buying my lenses. It was hard finding information about lenses. I didn't want to spend money on a lens I wouldn't use. The better understanding we have about our gear the better photographers we will be. I have never seen a class like this. Invaluable...yes I bought the class! I am really impressed with the high quality photography classes available on Creative Live!

Tami Miller

Have loved the other John Greengo classes I've watched & purchased - and this is another winner! Having been a high school/college science teacher, it is refreshing to take a course with someone who not only is extremely experienced, seems to be a computer having stored so much knowledge, but is equally concerned about making the information truly understandable to different levels. And he shares the information using every tool he can: slides, video, interactive presentations, and great quizzes. I learned so much about my Canon lenses - and lenses in general with their many components. I am excited about testing each of mine to see what macro ratio they handle, and especially appreciated the tutorial on testing each for their specific quirk that affects super sharpness. This class is great whether you own Canon lenses or not. Thanks John Greengo!


This was a great class not just about the lenses that Canon offers but also how each lens works. As usual, John's slides are alway informative and entertaining. There is a phrase: John has a slide for that! I am not even a Canon user and found this class to have great information for the use of each specific lens. Great work John! Thank you Creative Live for another great class!

Student Work