"Phil Lamerton" wrote in message
om...
I'd like to photograph a gray card outside on an overcast day, in
order to do some zone system testing with my new camera and lenses.

Since I will eventually be using the camera in the portrait studio
with a yellow/green filter, would it be wrong to do the testing with
the filter over the lens?

At the risk of incurring the rath of the previous responders, No, what you
propose is not a good idea.

The basic idea of testing the film speed, zone testing, etc, with the filter
in place is fine.

Doing the testing in overcast daylight where the planned use is in studio,
under tungsten or electronic flash, is a bad idea because the color
temperature of overcast daylight is much higher than anything you will use
in the studio. The studio response of the film/filter combination will be
quite different than your testing experioence, rendering the point of your
testing largely irrelevant.