In article <5es6gq$qmd@panix.com>, wbrodie@panix.com says...

>Thanks to those who responded in this thread and via E-mail.
>Now, a follow-up question:
>Different screens have different light-absorbing / light-transmitting
>properties. Metering, I would guess, is based on the light that makes
>its way through the screen. Does this mean that with each screen
>it's necessary to downgrade (or upgrade) the film speed setting
>depending on whether the screen transmits more (or less) light
>than the factory-supplied screen? In other words, if I'm using 50 ASA
>film and a screen that admits 1/3 F-stop more light, then should I
>set the film speed on the camera to 40 ASA? If so, do screens
>generally come with a number indicating how much compensation to perform?

Yes - and one would hope so..., but you can do a simple test...
Take a reading with the old screen in place, of an evenly (and
constantly!) illuminated surface. Replace the screen with the
new one, and do the same (without changing lens focus, angle
to subject, etc.), but adjust the ASA to make the reading the
same as the earlier one. The difference in the ASA setting is
the needed compensation for the new screen.
Hope This Helps