P3D Re: formats and focal lengths

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

Bruce's WOWs us with his Words Of Wisdom! I agree with his post,
and would like to add my own perspective. ;-)

It's been clarified that the perspective changes with distance
(between the camera and the subject) and not focal length. It
is very easy to demonstrate by sticking out your thumb in
front of you and moving your head back and forth (similar
to changing the distance of a camera to subject). You'll
notice the apparent size of your thumb change with respect
to other objects. This demonstrates that the persepective has
changed.

If you keep the distance fixed and change the focal length by
putting a magnifying lenses in front your thumb, the thumb
looks larger but so does everything else, thus the
perspective doesn't change (or true perspective as Dr.T
elaborates) with focal length.

Some might argue that a long focal lens is used in portrait
shots to give a more pleasing portrait (flattens facial
features). This is true but the real reason the long focal
lens flattens is because the shot is taken from further back.
Keeping the same distance but using a short lens and
magnifying to the same size, one would get the same effect
as the long lens.

The general confusion to understanding all this, is the
sloppy way we (myself included) explain these concepts.
Often times, a long lens is said to magnify or make things
look closer. A long lens does magnify BUT DOESN'T make
things look closer. These are two different things. Just
remember the notes about perspective changes with distance,
and everything will be 20/20! ;-) 

Gabriel