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[OM] Re: Choosing a mirror lens [was Firmware for Canon Printer]

Subject: [OM] Re: Choosing a mirror lens [was Firmware for Canon Printer]
From: Jan Steinman <Jan@xxxxxxxxxxxxxx>
Date: Mon, 19 Feb 2007 19:07:26 -0800
> 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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