keithr@tekchips.UUCP (Keith Rowell) (04/13/85)
What do you folks know about this?
I happily bought a used 200mm f4 micro internal focusing lens
because I figured it would do fine for general purpose and
closeup photography. I took a number of shots with it until
I started noticing in a few of my pictures that the edges appeared
in my Kodachrome slides (which I shoot exclusively) somewhat darkened.
Two shots in which this shows up particularly bad are these.
o A shot of a rose isolated against a solid
green background -- a lawn area.
o A shot of a flying swan against the sky.
After a while, I decided something was not right. So, I started to
analyze under what conditions the bad shots were taken. I noticed that
most were wide-open at f4. Finally, I took some test shots using
K64 of a uniformly illuminated blank wall. Guess what! Starting in
a series from f4, 5.6, 8, etc., to f32, there is what I take to be
*significant* light loss around the outside of the picture. This is
worst at f4 and gradually recedes to the edges of the picture at f5.6,
less at f8, till it finally disappears at f11, f16, f22, and f32.
I am aware that, especially fast, lenses suffer various optical degradations
at wide open and all the way stopped down. But, I must admit, I was
truly surprised to see the extent of this degradation in what I supposed
was a high quality optic from Nikon!
This lens has the older style, skinny tripod collar and is probably one
of the early versions of this lens. I should add that a friend of mine
has exactly the same lens of the same vintage (serial number is higher
than mine) and I tested his. I would judge that his is only marginally
better than mine in performance. I should also add that I had the lens
and my camera body (FE2) checked out at a Nikon authorized repair service.
He says he could see no problems and knew of no Nikon bulletins about
this. He looked at my test slides and agreed something was wrong with
the slide. And again I should add that I tested the lens on a friends
Nikkormat. The same problem showed up.
Anyone want a quality Nikon optic cheap? :-) (Just kidding.)
I would appreciate any further information, idea, comments about this
from you who are in the know. What gives with this Nikon crap? :-)ark@alice.UUCP (Andrew Koenig) (04/15/85)
J. Eric Roskos complains about a 200mm f/4 micro lens that gives slides with dark corners as f/4, and progressively less so at smaller apertures. This phenomenon is called vignetting, and virtually all lenses have it to some degree, regardless of manufacturer. The design of any lens is a trade-off among a number of factors, including sharpness, contrast, vignetting, size, price, and so on. A good designer will optimize a lens for the conditions in which it is most likely to be used. Macro lenses are usually used to take close-ups. Long macro lenses must be stopped far down to get any depth of field to speak of. Thus I would expect such a lens to be optimized for sharpness over a wide distance range, especially at small apertures. I would not expect vignetting at wide apertures to be high on the list of priorities. Incidentally, does your lens accept 52mm filters? It is virtually impossible to design a 200mm f/4 lens that takes 52mm filters without some vignetting. 200 divided by 4 is 50. Think about it. Photographing a subject in the center of the frame with a background of solid color and intensity on slide film is probably the most severe imaginable test of a lens's vignetting.
jer@peora.UUCP (J. Eric Roskos) (04/16/85)
> J. Eric Roskos complains about a 200mm f/4 micro lens > that gives slides with dark corners as f/4, and progressively > less so at smaller apertures. Now, wait a minute... I did no such thing! Keith Rowell has the vignetting problem. Gee... first they call me "?" in net.singles, now they attribute the wrong articles to me... what next! :-) (None of my lenses have that problem, thank you!) -- Full-Name: J. Eric Roskos UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer US Mail: MS 795; Perkin-Elmer SDC; 2486 Sand Lake Road, Orlando, FL 32809-7642