Is there a list of the mask dimensions for a Speed Graphic tube viewfinder? I have been meaning to ask this for a while, since I find that my father has been walking around for the last 50 years with a #3 mask in his viewfinder when the book says he should have had a #4 for a 135mm lens...I would suspect that the difference is negligible, but I'd like to know for sure.

Rob Dean

Measured dims equal
#3
20.8mm x 14.5mm
#4
22.9mm x 17.6mm