On 4/22/2015 5:29 PM, Chuck Norcutt wrote:
I have posted here <http://www.chucknorcutt.com/MLP/Mirror%20lens%20performance.pdf> what I think are the same data
Moose presented except that I have them in a much more readable format. Actually, I'm not sure where I found the
original data but laboriously entered it all into a spreadsheet and then produced a PDF from that.
I think if you review the data you'll find not much agreement with what you've said below. The Zuiko actually has
quite good resolution and has far superior contrast to all of the other contenders.
I know that was a big deal in film days. I can't see where it matters with digital. Shoot Raw, convert to 16 bit, use
Levels to pull the ends of the histogram out and adjust the midpoint if needed - - - and there you are, all the efforts,
successes and failures of lens design for contrast are washed away. Add LCE and Curves and you'd never know it wasn't
taken with a nicely contrasty lens.
The Vivitar solid-cats, on the other hand, actually perform quite poorly. They're the lowest on the list in
resolution and also very near the bottom of the pack in contrast.
The Questar, Honeywell and Celestron are superior to all the others in resolution but still lag well behind the Zuiko
in contrast. They are also quite different animals from the 500/8 lenses. They're proper telescopes and are
significantly larger and heavier.
Indeed. I have the Meade 1000/11, and it's a physical handful. I can't imagine using it successfully without a tripod.
Comes close enough to filling an APC-C frame with the Moon that I ended up fighting the Moon's motion to get it all in
frame.
And I don't know where you'd actually get a Questar 700/8. The only Questars I've ever seen or heard of are 3.5" or
7" Maksutov telescopes with focal ratios closer to f/15 than f/8. Even the little Questar sells for $5,000 or more.
If you really want a 500/8 mirror lens the Zuiko is actually a pretty good choice.
Absent the desire for lightness and compactness, and general OM coolth, I think the Sigma 600/8 is as or more useful.
Even with such long lenses I usually end up doing some cropping. Less cropping with the longer FL actually works out to
up its effective resolution for the same subject and display size, relative to the 500 mm lenses. I worked out the math
long ago. It's probably in some ancient post in the archives. Not doing that again soon.
Even so, I'm intrigued with the idea of hand holding with IBIS. Given the results I'm getting with the E-M5 II @ 300 mm,
that just might be useful. The lighter, shorter Oly could be better for that.
Long View Moose
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