AF Nikkor 20 mm f2.8 Vignetting

If there is a fairly sharp darkening only in the far
corners, this is vignetting, generally caused by a filter
and/or shade that cut into the angle of view of the lens.
If there is a slow roll-off of illumination only at wide
stops, this is normal and it generally is gone by f5.6
in good wide-angle lenses. BTW, much as I like the Nikkor
20mm f2.8 (and consider it one of the very best very-wide
lenses), I do not use it wider than f5.6 (where its
edge/corner performance "hops up" in quality) if at all
possible. (the lens can easily be hand-held at 1/15th, and
even 1/4 second is not difficult...). Lenses have optimum
stops for best performance, and that is one of several
consideration to be included in exposure decisions (which
is partly why I prefer manual exposure determination
to auto modes...).
David Ruether


#