In article <4i249a$q26@clarknet.clark.net>, css@clark.net says...

>I was trying to come up with a good subject for evalutating a new lens
>when I got an idea. I set up a 5000 K light box and placed a window
>screen in front. I set the camera up on a tripod, being carefult to
>align it with the center of the box and to keep it all square. I >metered for the light light source and shot several exposures at >different aperatures. This seems to be a good lens test. It produces
>a high-contrast, regular, fine pattern edge to edge. Comments?

It is a simplified version of a chart test, and shares some of its
advantages and disadvantages. To make it most useful (assuming that
the screen is actually flat, and parallel with the film), you will
probably need to do "focus bracketing" (changing focus in slight increments through "correct" focus) to avoid mis-focus, and to detect
(and get around) the effects of field curvature. Though your test
pattern has only one test "frequency", it should serve to see some
center-to-corner variation. It tests the lens at a rather close focus,
which puts many a fine lens at a disadvantage (lens performance varies with distance, often quite noticeably).
Hope This Helps