Quote Originally Posted by brucetaylor View Post
I was unsure about the plane of focus on an 8x10 camera. I wanted to confirm the gg position. I took an old holder and a hole saw, I drilled 5, 1" holes in a pattern, 4 corners and the center. I put a developed sheet of film in the holder. I removed the gg and put the holder in place. Wide open, I focused on a focus chart and with a loupe confirmed the targets were in focus. I then removed the holder and replaced the gg. Again with the the loupe I confirmed focus. In my case no adjustment was needed, but I think it would have been relatively easy to make gg shim adjustments to match my true plane of focus as determined by the film at the actual film plane.
This is a great method that I hadn't though of and should give accurate enough results! It's worth sacrificing a holder for IMO.

Doremus