On Mon, 20 Jul 1998 18:22:16 -0400, "Sherry L. Laflamme" wrote:

>In Pop Photo's Buying Guide (98/99) they use observations like "Light
>fall-off was gone by f/5.6 at 24 mm" (referring to 24-70 mm f/3.3-5.6 AF
>Sigma lens) or "there was no light fall-off at all at 50 mm and 70 mm"
>(referring to a 28-70 mm f/4 FA AF Pentax lens). I tried to find
>references to this term but have been unsuccessful. What does it mean?
>Is it good or bad?

B-a-a-a-d...! ;-)
Ideally, an evenly-illuminated subject would be rendered the same way
on film, but optics and economics sometimes dictate the acceptance
of less than ideal performance, so most lenses render images that
are darker at the edges/corners (softly... - sharper-edged darkening
is called "vignetting", usually caused by filter rims and shades that
are too deep, and cut into the image). This effect is worst at the
widest stops, and stopping down a bit often cures the problem.