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Re: COCs
>An interesting and informative discussion, but lacking in the one
>critical aspect of this discussion of major consequence: viewing.
>
>It is true that DOF will remain contant for various formats using
>"normal" lenses IF viewing conditions remain equal. That is a big IF,
>and I think in the case of our stereo photography we place higher
>demands on viewing than a normal "ortho" view of a gallary print.
>
>While a 0.8 mm COC might be acceptable for the Ricoh factory assuming
>standard viewing factors , they are likely inadequate for stereos higher
>orders of magnification and/or closer viewing distances, not to mention
>the tendency for stereopsis to demand greater DOF/smaller COC than might
>be tolerable with a mono view.
>
>Rollei BTW specified 0.5ish for MF I think and the 35mm standard is
>about 0.33 mm.
Good points Eric. I think you are missing a zero
from your COC numbers though. Isn't 35mm 0.03mm,
medium format 0.05 to 0.08mm?
To understand why the Ricohflex COC's are too
large for stereo: with my MF stereo viewer I view
the 50x50mm transparency from 80mm away. Suppose you
made a 5x5" print and hold it in your hand to view.
You will probably look at it from 15 to 20" away.
You would have to view it from 8 inches to see it
from "as close" as when you use the stereo viewer.
So the camera was designed for a less critical
viewing situation (3 or 4 times image width, rather
than 1.5 times in the stereo viewer).
The Rolleis have used a tighter COC number because
their customers were likely more critical users
(pros and serious amateurs) and made bigger enlargements.
Regards - Greg
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