Sean Chan writes:
Lenses
======
I've been looking at 3-4 main categories - 28mm F2.8, 50mm F1.4, 100mm
F2.8, 300mm F4. And I've also adopted the mentality of "Nothing but
Zuiko". Is this a fair guide?? How do the Tamrons, Tokina's, etc.
compare to Zuiko?? Needless to say, going for 3rd party opens up my
range and variety of combinations - but I sharp photos (in this case for
Astronomy - so pinpoint sharp stars are nice).
Ah, you test lenses the way I do :)
Zuiko lenses *used* to be state-of-the-art. Nowadays, with newer designs
and a greater variety of kinds of glass available, the third parties are
doing very well.
My Sigma 90/2.8 macro is actually sharper (at infinity, shooting star
fields) than my 100/2.8 Zuiko, although the Zuiko is very good and its light
weight is nice. The Zuiko seems to have a bit more chromatic aberration,
mainly.
My Zuiko 180/2.8 and 300/4.5 both have perceptible amounts of chromatic
aberration (bluish haloes around stars) -- not serious, definitely nothing
like a cheap third-party lens from the 1970s, but noticeable. I'd like to
test the Zuiko 180/2.8 against a Nikon ED 180/2.8; I'll bet the Nikon would
win.
So... Zuiko lenses are good but not always the best. Back in 1972 when
Olympus designed the Zuiko lens system, there was no ED glass. Also, they
kept the number of elements down, both because they didn't have multicoating
at the time and because they valued light weight.
I have a Sigma 300/4 coming soon (Nikon mount) and will test it critically
against the Zuiko 300/4.5.
By the way, as you know, lenses should always be focused on the stars --
don't trust the infinity stop (although to my surprise the infinity stops on
my Nikon AF 50/1.8 and Nikon AF 35-80/4-5.6 are exactly right).
Michael A. Covington / AI Center / The University of Georgia
Author, Astrophotography for the Amateur
http://www.ai.uga.edu/~mc http://www.mindspring.com/~covington <><
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