Equivalent focal lengths

Bart van der Wolf wrote:

"Colin D" wrote in message
...
SNIP
If the subject is two-dimensional, i,e, a newspaper page, then,
abberations aside, a wide-angle lens would give a distortionless
image. But, where the subject is three-dimensional, image
distortion occurs because the lens is projecting a 3D image
onto a 2D film/sensor.

As illustrated in figure 2 of
http://www.trenholm.org/hmmerk/SHBG07.pdf .

Bart

Thanks, Bart. I did try to find a supporting web page, but couldn't in
the time I had.

Colin