Focus Test

It's a good idea to make sure camera lens mount registration, and lens back focus are in spec and working together properly. One can shoot tests on film; of course a groundglass test is a lot quicker. A Nikon F focusing screen works great, twisted slightly so the groundglass sits on the inner film rails (NOT the outer guide rails!!). I had my local glass shop cut a small piece of frosted glass to use with Leica M. Note that glass must be small enough to fit inside the outer guide rails. (For a more sophisticated approach, check Rick Oleson's site for how to use an SLR as a collimator.)

I have found that groundglass tests match those on film....two errors cancel each other out. The image plane in the film is perhaps .03mm below the surface of the emulsion. But the film bulges a similar amount toward the lens. (A discussion by Erwin Puts of this issue is here.)

Typical focus test:

Suggest "download file to disc" and open in Photoshop:

Hi-res file: Helios-103 1981; Kiev-3 1956, target inclined at a 30 degree angle to optical axis, 1.7 meter distant.
Focus test jpeg, 140K, 2MB greyscale when opened in Photoshop

Focus Test Target
(600 dpi bitmap tif, 160KB)