On Wed, 07 Oct 1998 13:55:39 -0700, tbuckley@uvic.ca (Tom Buckley) wrote:

>David, did you use the same 24-120 you rated so highly a few months ago in
>your comparison? I wonder if you happen to have an unusually good one
>(following up on your point about sample variation)? The 24-120 I had was
>noticeably less sharp than the Nikon primes I compared it with and also
>noticeably less sharp than the 35-70 2.8. My sample certainly didn't rival
>these lenses at f8. Maybe my lens was at the other end of the sample
>variation scale?

This is entirely possible! I try to stress the possibility of lens
sample variation, and point out that the MOST variable tend to
be wide range zooms, especially ones that include wide-angle.
Most people are impressed with this lens, so I suspect you may not
have gotten a good one. I recommend that at least rudimentary lens
checking be done immediately after receiving a new lens. I have a
Nikkor evaluation list on my web page (under "I babble") that may
be useful in comparing a new lens with another one also on the list
that you have. The easiest way to check lenses may be to shoot
detailed distant material (with detail everywhere in the frame,
which may require taking multiple frames at a given FL/stop) at
all the marked FL's, and at least at f2.8 (if possible...), f5.6,
and f11. Use a decent 10X magnifier directly on the film. F11
should give you a good "best case" sharpness reference, unless the
lens is terrible (shoot a known lens on the same film, the same way,
for a better reference...). Look for equal 4-corner (and
opposite-edge) sharpness (without refocusing) to check for
alignment. Look for corner (and edge) sharpness compared with the
center. In a good zoom lens, the center should be quite sharp by
f5.6 (very nearly the same as the center at f11), with the edges
very good, and the corners OK (not mushy, though maybe not crisp);
at f11, everything in the frame should be reasonably crisp (though
a good non-zoom will generally outperform a good zoom, even at f11
[the 24-120 Nikkor, though, can just about equal good primes at
f11...]). Be aware that zooms, and some primes, may be quite
distance-sensitive for sharpness (if so, it is generally at close
distances that sharpness falls...), so I don't generally recommend
the "newspaper" test (some excellent lenses will fail it...;-).
As a lens-checking nut, I warn you, though, to avoid the dreaded
"lens-checking mania" that can sweep over one...;-) If the lens
works for you, be satisfied...! ;-)