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[OM] Mirror lenses [was Some OM500mm shots today]

Subject: [OM] Mirror lenses [was Some OM500mm shots today]
From: usher99@xxxxxxx
Date: Wed, 2 Mar 2011 17:49:49 -0500 (EST)
Summed up Moose states:

>Considering the 3D effect of FL on lens volume, and the tripod mount, 
only a
.28% weight increase is pretty impressive.
>Of course, the Zuiko weight includes the built-in hood and the Sigma 
doesn't
>include the hood, although it's quite light.

>Increase in length and diameter pretty much even out at the 20% 
increase in FL.

What a wonderful summary of performance and size differences. I saved 
this one.
Thanks, Moose.

Ed has a point that the central obstruction (secondary mirror) reduces 
MTF at low spatial frequencies.
As the reduction is uniform it should respond well to PP. Whether 
increasing global contrast or adding LCE reverses this
effect precisely or just partially corrects it, I don't know, but the 
images seem to respond nicely. Not much can be done for loss of 
resolution at higher spatial frequency. I wonder how the IQ compares 
after processing, but that is really a very difficult question.

The images with CAT lenses always seem to lack SNAP,
but CH's and others posted here contradict that. I wonder if his would 
make some nice large prints?

I do have a nice Celestron 750 f6 and had sniped at a couple Zen finish 
Sigi 600/8 ones and I think a camo one a few years ago.
I have since read that the latest flavor of this lens with the "Zen" 
finish can start to break down and become tacky and messy. Moose's 
plain black one seemed fine.

CH has a good point about packing density. If somehing goes in my 
travel kit now, something else has to stay home. :-(
I am going to keep an eye on these lenses.

One CAT household , but may change that, Mike

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