At last I understand how telephoto lenses compress!

[drr0b]

I've been reading around composition techniques for a little while, and I kept running into the concept that telephoto lenses somehow compress the different parts of the image together, while a wide-angle lens creates space between them. I did a little test, and now I see what's going on- it's quite simple really!

Here are two photos taken of the car across the road at different focal lengths, but with the same apparent size.

1) 70 mm


2) 95 mm


To get the car/van/whatever to be the same size in the second image as the first, I had to stand further away.

This means that for the first photo, I was much closer to the foreground car than the subject, while for the second photo the distance between me and the foreground car was more similar to the distance between me and the subject. This affects how we see the image because of something called parallax.

Imagine driving down a road where there is a nearby fence, some woods in the middle distance, and mountains further away. The fence goes by really quickly, the woods go by more slowly and the mountains hardly move at all... this is down to parallax. If there was one cow by the fence and another cow 20 feet away, then the nearer cow would appear to move more quickly than the more distant cow. However, if there were two cows by the woods, one 20 feet further from you than the other, then they would seem to go by at similar speeds.

The key thing is how the distance between subjects compares to the distance between you and the subjects.

For wide angle lenses, the distance between subjects is a larger fraction of the distance between you and the furthest subject, so parallax is more pronounced, and so we get a feeling of space between subjects

For telephoto lenses, the dstance between subjects is a smaller fraction of the distance between you and the furthest subject, so the parallax is smaller, and the subjects feel compressed.

I hope that makes as much sense to you as it does to me!

[wulf]

I think your explanation is right but it might be worth tracking down another scene to use to provide an illustration. Here the window frame and Syringa (lilac) obscure most points for comparison. Looking down the street might work better.

Wulf