In article
>I recently purchased a 500mm f/8 Mirror lens, made by "Sakar", for $150.
>I'm pretty unimpressed with the first roll of prints I got back.
>I am aware of the typical quirks of a mirror lens, like the dougnut
>focus blurs, extremely small depth of field, and fixed aperature.
>These I can handle.
>What bothers me is that even at its sharpest, it's very soft. I have
>two pictures of a helicopter in flight, one with a Canon 100-300USM at
>300mm, and one with the Sakar 500mm mirror.
>The Sakar picture is hazy and soft, even in the "sweet spot" of focus.
>The colors are a bit drab and contrast low, but I can live with that.
>The Canon is about what I would expect: nice colors, good contrast,
>pretty sharp. For small prints, the Canon is OK, while the Sakar
>looks out of focus.
>So here's the question: Did I get a lemon? Should I return the Sakar
>and get another mirror lens (like the Vivitar or Tokina)? Or, are all
>lenses of this design a bit on the soft side? (Maybe Sakar just
>sucks.)
>I hope I'm not expecting the impossible from a $150 lens, but I'd like
>to think that they can get a crisp picture in bright light. Is anyone
>out there happy with their f/8 mirror lens?
>To keep or exchange, that is the question..
Hmmm...., I guess, rather than answering your specific questions, I
will relate some of my experience with mirrors, since the answers are
not simple. My first experience was with an older-style Nikkor 500mm f8
borrowed from a friend long ago. I could not get a sharp photo with it
(using a tripod at medium speeds in poor weather), and returned it with
a low opinion of it. Years later, I tried another similar Nikkor on a
sunny day with Tri-X hand-held, and was surprised to find that a high
percentage of my images taken with it were quite sharp. It has become
a favorite lens, producing sharp images (even with a TC14 converter
attached to get 700mm) when used with an understanding of its limitations:
hand-held shutter speeds must be 1/500th or higher; tripod shutter
speeds must be either fairly high, or low, to avoid the 1/2-1/30th or
so "vibration" range (unless the tripod is not extended, is weighted
down, and the reflex mirror is locked up); air quality (heat uniformity
and freedom from contaminants [smog or fog]) must be sufficiently good.
Having tried some other mirror lenses, I have seen no others of similarly
high quality (including other Nikkors), though a newer-style Nikkor 500mm
f8 and a Minolta 250mm f5.6 were pretty good. The cheap mirrors were
uniformly terrible. the Tamron wasn't too bad. (I have not tried the
Vivitar Series I or Sigma 600mm's, though.) 500mm f8 mirrors, being
light and physically short, hard to focus, and with fixed (slow)
apertures, are easy to carry, but hard to use even when they are
optically excellent.
Hope This Helps