light fall off

[Ilesh Shah]

How to calculate light fall off on the edges of film? How to componsate for that? Minolta suggests to calibrate booster probe for each point of the ground glass that we intend to meter.How to simplify this?

[Ellis Vener]

How about using Polaroid and see what your film is actually doing? I strongly di strust the "measuring-through-the-groundglass" method for general photography be cause of just this problem as well as general clumsiness. The Sinar probe,connec ted to a Minolta Flash IV or Flash V or a Broncolor FCM meter is better, but you need a Sinar or a camera with a Sinar MB back. In any case, That method works b est when you are shooting for consistent reproduction qualities, such as limitin g contrast range, such as when you doing high volume catalog photography.

The fall off you see when looking through a groundglass has more to do with the optical qualities of the groundglass or groundglass fresnel combination than it does with the light striking your film.