Originally Posted by jimgalli
measuring the camera for the gear program is a little tricky and takes time to get it right. The program was originally put together by Bob Lang for the purpose of copying Cirkut prints at 1:1. This required gearing outside the normal set that came with the cameras. I got a friend to rewrite the program in a modern user friendly format then made it available to everyone.
You can effectively sidestep the program if you're prepared to do some testing. Setup a white target 3 foot square, put a black cross on it full width/height. Shoot the camera at 25 feet and infinity (200 x fl) or any other distance you plan to shoot the camera at. For groups you want 25 feet, landscape you can get away with 1 gear per fl.
After processing the film carefully measure the target, sometimes it helps to enlarge the target and print it. You could scan it and measure in photoshop.
The aim is to get the vertical and horizontal distance the same on the target. The vertical will remain constant, the horizontal will change with gear changes. When the gearing is correct the camera will pull exactly the right amount of film to make the target square.
Sometimes you see on Cirkut prints skinny faces, this is due to incorrect gearing for the focus distance.
Rotation cameras have a secondary focus which is achieved when film pull and focus distance are synchronised. Simply focussing the lens does not neccessarily give a sharp image like a conventional camera.
I tried the large cross thing, and didn't get a lot of difference in sizes. I found that it's helpful to have some fine vertical lines to look at for slur, or horizontal film blurring, which you get when the film isn't in sync with the lense image. I've used a combination of both, but the fine vertical lines seemed to show problems better.