• Articles about graphics and illustration
The hills in the distance look close together, but this is an
optical illusion caused by the relative closeness of the
The myth of perspective compression
Photographers — or more often photography publications — frequently make the
claim that the use of telephoto lenses will 'compress perspective'. I've
never been entirely clear what is meant by that; I presume that the desired
is to make objects that are distant from each other appear closer together.
In fact, there is no such thing as perspective compression. The
significance of the telephoto lens is that it allows the photographer
to stand further from the subject Hardly magic, but visually
relevant all the same.
This article was prompted by something I read on another Web site, in
which a photographer tried to disprove the myth of perspective
compression by taking a series of pictures at different zoom settings
while standing in the same place. He then edited the photos so that
each showed the central subject at the same size and — wonder of wonders — they all looked the same. There is, the author claimed, no such
thing as perspective compression.
That's true, of course, so long as he was standing in one spot. All he
was doing in a test like this was to use the computer to compensate for the
variation in field of view of the zoom lens. There might be some small
variation in depth of field across the images but, otherwise, we'd
expect them to look much the same.
The two diagrams below are intended to show the relationship between
lens focal length (or, rather, angle of view), impression of perspective,
and photographer position.
In figure 1, the photographer is using a lens with a 30-degree
field of view. If the viewpoint is such that the trees fill the
frame, then the trees are relatively separated, compared with their
distance from the viewpoint. Features of the front tree that are
the same size as those of the back tree would appear roughly
twice as large in the photographer, simply by virtue of the
photographer's close viewpoint.
In figure 2, however, the field of view is only 15 degrees. The trees now fill
the frame with the photographer's viewpoint much further away than
in figure 1. Unless the trees were actually directly in line (so that
the viewer could see that one was in front of the other), they
would appear to be about the same distance away in the photograph. That's
because features on the two trees would now appear to be about the same size
in the photograph.
We might talk of the second photograph as showing 'compressed perspective',
but all that's really happened is the the camera has been placed in
such a way as to make features of the subjects appear similar in size.
Perspective compression is an illusion, caused by the way our brains
process size and distance cues.
And that's all there is to it. You can't adjust the impression of perspective
simply by fitting a lens with a longer focal length. The effect on
perspective comes from changing your viewpoint.
Comments welcome, as always.
Figure 1: with a wide-angle lens the photographer must
stand close to the trees (the subjects, in this case )
for them to fill the frame. Compared
to the distance from the photographer to the subjects, the
subjects are far apart
Figure 2: with a telephoto lens the photographer can
stand some way from the subjects and still have them fill
the frame. The subjects are close, relatively speaking, compared
with their distance from the photographer's viewpoint.