calculating aperture scale - an easy way?

[Michael Graves]

I'm in that same situation. I have a 360 that the shutter crapped out on. It fits perfectly into the Copal 3 that my 300 is in. I just did a different film speed test for the 360. When shooting with the 300, I use one film speed. When shooting with the 360, I use the other. Crude; but effective.

[Paul Fitzgerald]

Tim,

You can measure the apparent aperture by putting the lens assm. on a lightbox and put a sheet of frosted glass/ acetate/ paper across the front lens. You can do the math to find the needed sizes and draw them out on the paper. Stop down until they match and mark your tape.

(Actually this should be done with a point-light source at the focal length for inf. but the lightbox is easier.)

Have fun.

[Jason Greenberg Motamedi]

To follow up on Paul's suggestion, I have used a laser pointer as a point light source. IIRC I focused the camera on infinity, locked it down, and then pointed it at a white wall parallel to the camera. In a darkened room I pointed a laser pointer at the center of the GG and measured the size of the light which was projected through the lens with a calipers. This should be pretty close to the size of the apparent aperture.