In article <56gpep$4jp@hpg30a.csc.cuhk.edu.hk>, bmtong@cse.cuhk.edu.hk says...
>
>David,
>
>May I have your permission to put this review of yours in the Nikon FAQ?
>
> Bo-Ming Tong

Yes, but please attach the last paragraph (about copying and copyright)
from the "SUBJECTIVE Lens Evaluations (Mostly Nikkors)" article. Thanks.
Here is a slightly updated version (since seeing a roll of color slides):


The Nikkor 24-120mm F3.5-5.6 AF-D Zoom ------

Here it is, some info on the Nikkor 24-120mm f3.5-5.6 AF D
(under $600, including shipping in US from B & H in NYC...).
All infinity-focus negatives were shot using a detail-filled
hillside (buildings and trees) as subject, about three miles
away. 4'-distance negatives were shot pointing straight down
at a weathered-concrete sidewalk surface. The first roll of
negatives were shot at marked (not actual, since this is a
variable-aperture zoom) f5.6 hand-held on Tri-X rated at 400
and processed in FG-7. The lighting was from an overcast sky,
with a shutter speed of 1/500th, based on a compromise
exposure taken at about 55mm. Vertical negative pairs were
shot at about 24, 28, 35, 40, 50, 60, 70, 85, 100, and 120mm
with the horizon at the top of the frame (shutter release end
up) for the first frame of the pair, then the camera was
carefully inverted for the second frame (without refocusing)
of the identical subject (this provides the same detail
at the edges of the frame across the frame line, making
comparisons for checking alignment and corner sharpness
easier). Frame pairs were also made at the marked 24, 28, 35,
50, 70, 85, and 120mm positions with the horizon line running
from corner to corner, first in one orientation, then the other
(this is a good check for center to corner and center to edge
variation, and provides a good check for consistency between
top and bottom corners at each frame side). The second roll of
Tri-X was also rated at 400 ASA, but was processed in D-76 1:1.
Lighting was clear sunshine. Frames were shot at marked f5.6,
then at marked f11, this time using aperture priority auto to
keep negative density uniform (I was interested in seeing how
sharpness changed with aperture). Only diagonally-placed
horizons and the sidewalk were shot on this roll, since the
first roll showed me what I wanted to know about alignment.
I then shot a roll of Kodak Elite 100 slide film, since some
lenses (especially wide angles) show differences in edge and
corner performance at wider apertures with B & W film vs.
color transparency film. Transparency film checks are also
good for showing overall lens brilliance and contrast
characteristics. Manual focus was used throughout.

This is what I found with THIS SINGLE SAMPLE (optical
performance tends to vary much more from sample to sample
with zooms than with primes):

- The lens takes a 72mm filter, which does not rotate
while (IF) focusing, but the front does rotate about 80
degrees during zooming through the whole FL range.
- The lens is about 3" across, and about 3.5" long at
24mm and infinity-focus, but it grows considerably (the
front telescopes out) while zooming from short to long,
becoming about 5.5" long at 120mm (though it is remarkably
compact, given its range). It is a bit front-heavy on light
bodies, but balances well on AF bodies. It seems not to
have excessive "wobbles" or play, but it does "self zoom"
when turned up or down, even though it is a two-ring type
zoom.
- The lens is slow at the (not very) long end, though
fast enough at the short - maybe it should be considered
a 24-85mm that can lengthen more, when needed...
- This sample is slightly vari-focal (not unusual for
Nikkor zooms), with a smooth shift from marked 10' for
correct infinity focus at 24mm to correct focus at the
focus marks at 120mm. (This may be correctable in this
particular sample, using paper shims under the bayonette,
but I will probably not bother to do it.) The lens focuses
to just over 1.5' throughout its range - which is remarkable
for a wide to short-tele wide-range zoom. The focus is
rather fast (with short focus-ring movement from maximum
to minimum focus distance), but it is easy to control in
MF over most of the zoom range, and AF seems to work
reasonably well with this lens throughout its range.
- Distortion is present throughout its zoom range, but it
is very moderate. It is pincushion above about 35mm, and
wavy-line type below - and it increases only slightly at
the FL extremes. There is no FL at which distortion is "0".
- Illumination at the marked f5.6 stop is remarkably even.
- Flare is very minor, but there is a tendency to ghosting
with the sun in, or just out of, the frame - and the
available shade is unlikely to be much help in preventing
it (using a hand to shade the lens from small very bright
light sources, when possible, may be the best shade for
this 15-element lens).
- Contrast, brilliance, and color rendering over most of
the frame are Nikon-normal (excellent).
- Alignment (ability to render the four corners and
opposite frame sides equally sharp without changing lens
settings) in this sample was not perfect, but was better
than I have seen in most wide-angle zooms - the variations
at f5.6 were just detectable with a 10X magnifier, and
should be undetectable by f11 (excellent performance for
a wide angle, wide-range zoom, though near-perfect alignment
is common in Nikkor tele zooms, and in most Nikkor primes).
- Sharpness on Tri-X was surprisingly good throughout at
infinity-focus and marked f5.6, and unexpectedly good at
the short end, where performance was excellent across most
of the frame, and very good even in the corners at f5.6.
Sharpness declined smoothly with increasing FL, being very
fine through about 85mm, and still good at 120mm, but with
slightly soft corners at 120mm. The lens showed no outright
softness anywhere at the marked f5.6, which is remarkable.
In color at f5.6, a very slight "diffuse" look appeared at
the corners about 85mm, becoming somewhat more pronounced
as the lens was zoomed toward 120mm. At f11, the
infinity-focus frames on Tri-X looked like those shot on
Technical Pan with excellent primes - images were crisp and
wirey to the corners, except for slight corner softness
near 120mm. At about 4' (zooms often vary considerably in
performance quality with distance) and f5.6, most of the
frame was exceptionally sharp throughout the wide zoom range,
but the edges declined slightly in the 35-50mm range, and
edge/corner performance peaked again in the 70-85mm range
(with excellent performance to the corners again, as with
the 24-28mm range), followed by a decline at the corners
as 120mm was approached . This overall performance level
is remarkable for a zoom, especially one that includes
the wide-angle range.
- I did not check FL extremes for marked FL accuracy.
More checks at another time...

Conclusion:
- At the short end at f5.6, performance rivals good primes.
- At the middle at f5.6, without much decline in performance
level, the excellent primes in this range surpass the good
edge/corner performance of this zoom.
- At the long end at f5.6, performance is only slightly
further reduced, but the truly excellent primes (and a few
zooms) available in this range do easily eclipse the
performance level of this lens. Overall, the lens is very
good at (the marked) f5.6.
- At f11, performance rivals good primes from 24-85mm, and
is it still excellent out to 120mm. This is a really fine
lens at f11, and it is fully able to substitute for the best
primes (for most purposes) over most of its range at f11,
making it a very useful lens for many types of photography
(and it focuses conveniently close, unlike most wide-range
zooms). I like this lens, even with my general reservations
about the usefulness of wide-angle zooms...
David Ruether

Consider all of the above to be copyrighted material
(1996 - David Ruether) which may be used freely for
non-commercial purposes. If this material is reproduced,
reproduce it as is and as a whole (unexerpted), including
this paragraph - and please let me know where it appears.
Thanks.
"Hope This Helps" (David Ruether -- d_ruether@hotmail.com)