When you have chosen a lens size (or a
particular focal length on a zoom lens) for a certain subject, you have
taken an important step toward determining the perspective your picture
will have. Perspective simply means how foreground objects appear in
relation to those objects farther back in a scene - relative size,
relative position and relative importance. A big close up of a man's
face with a tiny mountain range showing in the far distance gives a
much different impression than a picture of the man's full figure
overshadowed by huge mountains looming in the near distance. How to
control perspective in camera photography? This is a technique on
coordinating the space in a photo and understanding the relation
between background and subject to be photographed.
Lens focal length, as we know, determines image size from any one
particular distance. However, there is a corollary: lens focal length
also dictates lens to subject distance when image size is kept the
same. At a distance of 2.7m (8ft) from a man a wide angle lens may give
you a picture of his entire body. At the same distance a telephoto lens
may give you only his head. The magnifications are entirely different.
If you wish to include his entire body with the telephoto lens, you
will have to move back a good distance.
The increased distance between you and the subject will give you a full
length shot as with the wide angle lens, but what a difference there
will be in the background! Everything in the distance will be much
closer with the full length telephoto shot than with the wide angle
shot. That is because the telephoto lens has magnified every object in
the picture quality. You have moved back so that when the man is
enlarged you will still get his whole body into the frame. You were
close to him to begin with, so moving back a short distance includes a
lot more of him. However, you have moved very little in relation to the
background. Therefore, when the background is magnified along with the
man, it appears much more prominent than in the wide angle view. You
have changed the perspective.
Perspective in photography would appear to be controlled by the lens focal length, but
that is true only to the extent that the focal length determines how
far away from your subject you will have to be to get the image size
you want. Actually, it is camera position and camera to subject
distance that control perspective and dictate how the various parts of
a picture will appear in relation to one another.
For further proof use just one of the two lenses and take two more
pictures. This time take the shots at two distinctly different
distances from some nearby object. A full print from each of the image
will show that the foreground object has changed in size and position
in relation to the background when the camera was moved.