The point of the experiment was to illustrate that all of this
talk of "proper perspective" as expressed as a single lens focal
length, is a complete ruse. To clarify a bit further,
perspective is entirely a question of camera-to-subject
distance. Different focal lengths obviously provide a different
angle of view. If you fill the frame with a same-sized subject
with two lenses of different focal lengths, simple trigonometry
tells us that that means a different camera-to-subject distance
and therefore a different perspective. Depth of field and
background blur is a function of aperture -- but not the
f/number; rather, the actual physical size of the aperture. So,
do the actual division and you'll discover that a 50mm f/2 has a
50/2 = 25mm physical aperture, and a 200mm f/8 has a 200/8 =
also a 25mm physical aperture. So, if you stand in the same
place and take a shot with a 50 f/2 and 200 f/8 and crop the 50
to the same angle of view as the 200, you get, for the most
part, an identical image. Obviously, 200/2