On Wed, 15 Feb 2006, [EMAIL PROTECTED] wrote:
Logic would suggest that if exposure were affected by a change of screen, it would be off by a consistent amount in a specific direction. If exposure is "all over the place," I would think that it can't possibly be the fault of the focusing screen. Paul -------------- Original message ---------------------- From: Charles Robinson <[EMAIL PROTECTED]>
If it were a plain screen, that's probably true. The trouble is, the split-prism type screens work differently with different lenses and aperture settings. The "black-out" phenomenon depends on the angle from which the incident light comes. That's a function of the lens construction and aperture setting. It's that "black-out" phenomenon that causes erratic exposure problems. The "baseline" calibration is affected by the regular portion of the screen and doesn't change. That's the +1/3EV or +2/3EV or so often talked about.
-Cory -- ************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
