Clarifying Lens Compression


Today’s Question: Can you amplify regarding telephoto “compression” in an image such as a row of telephone poles that look like they’re only inches apart but are in fact many yards apart when shot with a long lens? I have always heard this referred to as “telephoto compression”.

Tim’s Quick Answer: The compression effect we experience when using a telephoto lens is really caused by being further from the scene we are photographing when using a lens with a long telephoto lens. The longer focal length lens is effectively cropping the scene, but the perspective change is caused by a change in position, not the lens itself.

More Detail: I should hasten to point out that the discussion of “telephoto compression” is really an issue of semantics. When you change two variables, it is perhaps inevitable that some people will say the first change caused a result, and others will say it is the second change.

Those who suggest it is the longer lens causing compression of the scene point out that to retain the same framing of the scene when you move farther away from a scene you must use a lens with a longer focal length. That is true, but that relates to the field of view, or the “cropping” of the scene.

The actual change in perspective that we refer to as “compression” of the scene is a result in changing your position relative to the scene.

Let’s assume I am recording a video of a person standing on the New Jersey side of the Hudson River, with the New York skyline in the background. I can move the camera closer to or farther away from the person, and their size within the frame will change rather significantly. The size of the New York skyline, however, won’t appear to change at all, because the relative change in distance is so much less.

It is that movement closer to or farther away from the scene that causes the change in perspective, based on changes in the relative distance to different objects within the scene. The long lens is simply cropping the scene to a particular field of view.

Put another way, if you move closer toward or farther away from a scene, the perspective will change. If you stay in one position and use lenses of different focal lengths, the perspective won’t change (ignoring distortion caused by extremely wide-angle lenses, of course), only the cropping of the scene will change.

You can see a visual demonstration of the change in perspective as you change distance relative to a scene in my “Lens Compression Myth” video, which you can find on the Tim Grey TV channel on YouTube here: