> From: Moose <olymoose@xxxxxxxxx>
>
> Chuck has made some comments on DOF calculations. They dont' square
> with
> my experience with mirror lenses. The issue is that most DOF
> calculation
> assume a relatively modest magnification for viewing. With mirror
> lenses, I find myself quite often cropping and blowing them up a lot
> more. That results in shallower effective DOF.
Keep in mind that DOF is affected by the aperture *and the FINAL
reproduction ratio.*
So if you do a 50% crop on a 500mm shot, the DOF will be the same as
a non-cropped 1000mm shot.
But the fact that a lens is good enough to allow such cropping is
GREAT! Think of it -- the 35mm equivalent field of view of a 2000mm
f8 lens, just by shooting on 4/3rds and cropping 50%.
Of course, you can't get away with that with just ANY mirror, as I
hope my study shows. But the Zuiko Reflex appears to be up for that
amount of cropping, and more.
http://www.Bytesmiths.com/OM_Tele/index2.html
> There are also specific issues with filter capability of different
> makes. The Zuiko 500/8 requires large, expensive 72 mm filters.
I have a superstition -- not supported by technical reasons -- that
the Zuiko Reflex doesn't respond well to filters. I'll have to do a
real test.
:::: Because you're selfish, it should be harder for everyone else to
read?
:::: > But it's easier for me to write!
:::: >> It's hard to read and follow.
:::: >>> What's wrong with top-posting?
:::: Jan Steinman http://www.VeggieVanGogh.com
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