At some point in time you will need to collimate a lens/camera.
I recently serviced a Frank Six TKS shutter, and I had to unscrew the front cell. As the camera not a through the lens viewfinder, I am not sure if the lens has been correctly set for infinity focusing … how do I know I screwed it back on the correct starting thread ?
This is where you need to check with a lens callimator … well I do not have such a dedicated machine, so lets go with a DIY solution … so I checked the web. There are many online docs about this (I noted some below) … so here is what I did.
First you need to have a camera to mount the lens on … unless the lens is part of the camera … then you need to put something on the film plane for the calibrator to focus on, then you need a second camera with a (preferably) telephoto lens to be the calibrator, and lastly some light.
- I cut down the clear plastic from an old CD case (a Dremel is really handy for this) to about 61.5mm x 63mm (in this case the camera was Frank Six 6×6 format). I roughly sanded one side to make it a ground screen, and used a Sharpie to make some marks on it.
- Sony NEX-6 with an adapted Minolta MD 135mm f/2.8 lens
- USB LED light
I taped the “ground screen”, ground side inside, to the back of the camera. I pointed the LED light to shine on the screen. The Frank Six lens was set to infinity.
The Sony NEX was positioned right up to the Frank Six lens as close as possible but left enough room for me to turn the front lens cell, and the Minolta lens set to infinity.
Using the Sony live view and flip up rear screen, I was able to see if the marks on the ground screen were in focus, or not. First try it was not, so I back out the front cell and tried a different starting thread … until the Sony showed an in-focus marking. Done.
Callibrator Camera+Lens — infinity — Lens+Camera+target
As I mentioned … more detailed info can be read below: