Joseph, Photography

You Asked For It – Focal Length And Perspective

Please note: Today will be the last of the daily posts.  The Visual Chronicle posting schedule will change to three times weekly instead of daily. I will post photos on Tuesdays and Thursdays, and on Fridays the weekly tutorial will continue. I would like to thank all of my followers and viewers that stopped by daily for the past two years and I would love to continue posting every day but truth be told between Monochromia and The Visual Chronicle it is just taking up too much of my time. It’s time to relax a bit after all I am retired 🙂

This is the fifth installment of the “You Asked For It” series and today I would like to discuss Focal Length And Perspective.  This post is going to be a little easier to understand than the previous two posts so all of you can breath a sigh of relief.

Before I begin I have to make one point which is how focal length applies to sensor size. For those of you with cameras equipped with a full frame sensor you could either skip this paragraph or take a short little nap, your choice. Most people who are either beginners or more advanced photo buffs will have a camera equipped with an APS-C size sensor. Nikon calls this DX format. Being a APS-C size sensor is smaller than a full frame sensor we have to keep in mind there is a focal length multiplication factor whether we are using prime (fixed) or zoom lenses. This multiplication factor is 1.5x which simply means whatever focal length you put on your camera the effective focal length will be 1.5x what is written on the lens. If you were using an 18mm lens the effective focal length will be 27mm (18 x 1.5 = 27). If you were using a 50mm lens the effective focal length will be 75mm (50 x 1.5 = 75). Easy peasy right ?

Focal Length

Now that we have that out of the way I would like to discuss how and why you would need different focal lengths. If you are a casual shooter you probably will never need anything more than the lens that came with your camera which could be 18-55mm, 18-105mm or even 18-135mm. You are probably just going to use the camera for family snapshots or birthday parties. But for those of us who get bitten by the “bug” you will probably be adding some lenses to your camera bag.

If you are shooting with a APS-C sensor here are a few suggestions:

  • 14mm which would be an effective focal length of 21mm (you will absolutely hate a wide angle lens until you learn how to properly use one)
  • 35mm which would be an effective focal length of 52.5mm (this is considered to be a normal field of view similar to what our eyes see)
  • 60mm which would be an effective focal length of 90mm (this could also be a macro lens which doubles as a great portrait lens)
  • 80-200 zoom lens which would be an effective focal length of 120-300mm

Now that I have all of you twitching about all of the money you will have to spend let me explain.  Different focal lengths change not only magnification and field of view but also perspective.  Lets deal with field of view first.

DSLR-focal-length-angle-of-view

As you can see the above chart describes how focal length relates to field of view.  If we look at the 135mm lens we will see that in addition to having higher magnification than a normal 50mm lens it also has a narrower field of view which is 18 degrees versus 43 degrees on the 50mm.

So what does all this mean Joe ?

It simply means if you need a chisel don’t use a screwdriver 🙂  In other words there is a reason manufacturers make all these different lenses, so you can choose the correct tool for the job.  If you wanted to take some photos of your recently remodeled kitchen you would not use a 50mm lens, you would use a 14 or an 18mm lens to have a wider field of view this way you can get the whole kitchen in the photo.  A different example would be if you were a bird watcher and you went birding with your friend.  You show up with a 50mm lens and after your friend stops rolling on the ground and laughing he says to you what do you expect to do with that, I’m shooting with a 500mm lens.  You would want a longer focal length for more magnification, you would have to get too close to the birds with a tiny 50mm lens.

Make sense ?  I thought so 🙂

Perspective

Now I would like to show you how focal length changes perspective.  I will show you three different photos of the same scene taken with different focal lengths.

Example-1

Oh boy Joe a photo of a dog crap bag dispenser, I was wondering when you were going to post one of these, LOL. I really don’t want you to concentrate on the dispenser, but I do want you to notice how the background relates to the dispenser. This photo was taken with an 18mm lens. What effective focal length would that be on my APS-C sensor camera ? Thats correct Laurie 27mm 🙂  All three of the photos were taken at an aperture of f/11.  Notice on this first photo how the background has depth or separation from the dispenser.  You can see the trees in the distance along with the walkway and a home.  Now lets try the same scene with a 35mm lens below.

Example-2

If we don’t pay any attention that I shook the camera a little on this shot you will notice that there is not as much depth to the scene.  This also was taken at f/11 with a 35mm lens which would be what effective focal length on my APS-C sensor camera ?  Thats correct Pauline 52.5mm 🙂  You can start to see that even though the magnification is higher on the 35mm lens than the 18mm lens the perspective is also changing because of the compression of the background in relation to the dispenser.  Did you notice anything else ?  The field of view got narrower, we see less of the scene than with the 18mm lens. Now lets try the same scene with a 200mm lens below.

Example-3

OK now we can clearly see a huge difference on the perspective on this shot.  Notice how close the tree looks in relation to the dispenser.  The 200mm lens flattened out and compressed the perspective on this shot.  By the way what is the effective focal length of this lens on my APS-C sensor camera ?  Absolutely correct Elina 300mm.  Notice how narrow the field of view got with this lens.

The more you get out and shoot with your camera and experiment with different lenses or zoom lenses the faster you will understand when to use a particular focal length and how you want the perspective to look.

Next week I will discuss why you should shoot (RAW) don’t get upset (or be disappointed) you will still be fully clothed, vs. .jpg 

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13 thoughts on “You Asked For It – Focal Length And Perspective

  1. I love these tutorials Joe, your approach to teaching is wonderful! 🙂 It is true it takes a while to learn to be friends with a new, totally different lens (at least for me it does). I’d love to have some more primes like Patti. 🙂
    ps. They should put such signs and instructions up for dog owners here in Finland. (I wonder why there are no)

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    • Thank you very much Elina 🙂 You described a different lens like friends and that is a very good comparison. Any change in the angle of view you are seeing through your viewfinder is like making a new friend. You mentioned you love your 50mm lens and I bet because you are so used to the angle of view that you can see your photos in your mind before you even pick the camera up to your eye. Just like an old trusty friend you are accustomed to it. Have a great day 🙂

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    • Thanks Patti 🙂 I have a full frame Nikon and APS-C Fuji’s and I tend to use the APS-C more, LOL. Its just a matter of being able to carry more equipment with less weight (old people like me have problems like that, LOL). Have a great weekend Patti 🙂

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  2. I recently purchased the “nifty-fifty” fixed lens, Canon EF 50mm f/1.8 II which I added to my old ultra-zoom lens, Canon EF 75-300mm 1:4-5.6 II. Currently reading about the Canon EF-S 10-18mm f/4.5-5.6 IS STM wide angle lens. It seems to be a very good lens for architecture photography.

    Thank you for your excellent Friday’s tutorials. I’ve read them all.

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    • 50mm lenses are the best bargain I don’t know why they are so inexpensive Omar. The wide angle would be equivalent to a 15-27mm which is still pretty wide 🙂 I appreciate you taking the time to read these articles every Friday, thank you 🙂

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  3. Yay – I got one right! 🙂 I must be retaining something Joe, I actually understood what you were talking about this time. Next thing I’ll be taking decent photos 😀 And of course the photos themselves make it so clear. Are you sure you weren’t a teacher in a previous life?

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    • I’m glad you understand what I am talking about Pauline 🙂 I’m pretty sure this is my first life but in my next life I want to be a dog, then maybe a teacher in the life after that 🙂 Have a wonderful evening.

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