Re: Camera film for enlarged negatives?

Ryuji wrote:

> I keep a 135mm lens on Copal selt setting shutter on my enlarger to do
> quick sensitometric tests on emulsions.

That's another good reason to shutter-mount an enlarging lens, and makes
testing for the zone system (or any personalized exposure/development
system) much, much easier. Generally, we want sensitometric data for
daylight -- 5500 K -- so one needs to filter the enlarger light. For a
typical old enlarger with a 211 or 212 lamp, either a B&W KB20 or a
combination of Wratten 80A + 82C will work. For an enlarger with a halogen
lamp an 80A or 80B should work. With a color head you would dial in some M
and C -- I'd have to look up how much. I don't think you could filter a
cold cathode lamp to 5500 K effectively, because they put out almost no red.

Be aware that testing film this way does not account for the flare in your
camera lens, which has a significant effect on deep shadows (Zones I and II
for zonies). If you project the step tablet rather than contact printing
it, you substitute the flare of the enlarging setup for the camera lens
flare. IMO, one is better off contact printing the step tablet and in a
separate operation determining the flare of the camera, then calculating
the effective in-camera film curve.

Best regards,

etienne
Received on Sat Aug 28 17:22:04 2004