Comments on: The Curious Case of Lens Compression

By: Carrie

Carrie — Tue, 08 Feb 2011 03:11:39 +0000

“please note that all focal lengths are in 35mm equivalent. That means If you’re not using a film camera, D700, D3, 5D MkII, or 1Ds… you need to multiply these numbers by roughly 1.5x. A 50mm lens on a Nikon D90, for example, would look the same as a 75mm lens would look on a film camera.” Found this as I was researching this topic online and remembered your question. (Source:
http://www.seanmolin.com/blog/?p=69)

By: Sean

Sean — Sat, 23 Oct 2010 05:09:35 +0000

Hi All. This site is amazing. And thanks for your comments on compression. I thought I knew what it was and I did for the most part but this solidified it. Another article mentioned you can visualize the same effect by looking through, say, a toilet paper roll vs. a paper towel roll if you maintain a distance that keeps your subject with the same composition with the two.

Jesse, if you’re not already familiar with the concept, which you probably are, you should test it with your own shots of possible familiar subjects to your audience. Just a thought as the relevance may have more impact.

By: Bomba

Bomba — Thu, 19 Aug 2010 18:00:05 +0000

Matt, Bob is correct. The first two example pics were taken from two different distances (a requirement to make the foreground model appear roughly the same size in the frame). Bob’s hypothetical example states that the two pictures need to be taken from the same spot.

It is a confusing topic, and one can utilize the lens compression effect successfully while remaining mistaken about the nature of said effect. If you have a basic understanding of optical physics, the following PDF very succinctly explains the phenomena correctly as a function of the distance to the subject:

http://scubageek.com/articles/compression.pdf

By: Matt

Matt — Sat, 24 Jul 2010 01:09:18 +0000

Bob, did you not see the first example? The person in the background is twice the size that he was in the first shot while the primary model is only slightly larger, If you resized the first shot to make the male model the same size that he is in the second, you’d only see the female model’s abdomen (not to mention the building in the background which is about 4x as large).

By: Jesse Alwin

Jesse Alwin — Thu, 03 Jun 2010 00:33:12 +0000

May I have permission to use these example photos in a presentation about Lens Compression?

By: Florian

Florian — Mon, 15 Feb 2010 21:32:14 +0000

… oh, sorry, I almost forgot: thanks a lot. Never tried this out… I knew this theoretically, but personally, I think, the pictures you provide are somewhat of an eye-opener.

By: Florian

Florian — Mon, 15 Feb 2010 21:14:29 +0000

AFAIK 50mm is about the diagonal size of a full frame, while 35mm is about the diagonal size of APS-C. The focal length is considered “normal” when it’s about the same as the diagonal size as the film (or sensor) format. This has actually nothing to with seeing the same thing through your viewfinder and your naked eye, as it varies from camera to camera, depending on the magnification of the viewfinder (try your 70mm on a pentamirror vs. pentaprism).

By: Jonte

Jonte — Thu, 01 Oct 2009 10:32:21 +0000

The 70mm vs 50mm thing… There is a difference between focal length and equal size.

I believe classic 50mm is the same focal length. When you talk about seeing the same thing it is a question about more than just focal length. Probably mostly magnification.

When we talk about the same focal length as the naked human eye you have to compare elements in the image to each other. I.e. two elements are placed at different distances. If they look like 1:2 with the eye, they should do the same through the viewfinder. Then you have the human focal length, but not necessarily field of view or magnification…

Or compare with prints. Make one small print and one huge print. They still both have the same focal length. But one apears much bigger than the other.

Or actually you can take any print with any lens. Go back to the original scene. At some distance it appears the same as the original. Magnification!

By: Andrew

Andrew — Wed, 30 Sep 2009 08:46:41 +0000

Coincidentally I just noticed the 70mm thing about 15 minutes before I found this article. I was playing with a superzoom “holiday” lens and I noticed that when I kept both eyes open I could zoom to where the left and right eye see essentially the same thing. When I took the camera away from my eye it was set to 70mm. Btw this was with a Canon XTi and a Tamron 18-270

By: David

David — Sun, 27 Sep 2009 14:24:00 +0000

Bob isn’t wrong at all. With the “vertigo” scenes mentioned by Mahmoud, the effect is produced by the dolly moving towards/away from the subject, thus changing perspective. All the zoom does is keep the subject the same size, which is what makes it seem so unnatural.

When photographing sunsets, the Sun appears about the same size wherever you go. However, if you want a foreground element as a silhouette, e.g. a tree, then you can move closer and further away from the tree to make it bigger and smaller, while the Sun remains the same apparent size.

For example, say you want to photograph the sun with a tree which is close to you. You want the tree to fill the frame so you zoom in, say, 2x. This is great but the sun is only 2x bigger than normal.
You then back up several hundred metres and photograph the same tree with the sun behind it, but because the tree is so far away you have to zoom in much more to get it to fill the frame. This time you have to zoom, say, 20x. The tree looks more or less the same but the sun is now 20x bigger than normal, compared to 2x in the previous shot, so the two pictures look completely different.