Collimation made easy
Take a piece of clear acetate and cover the aperture window (sellotape* top and bottom)
Pre-collimate to within the film bounds (this will be repeated with each cassette size)
With a medium to thick felt tip pen and a ruler and draw a line on the edge of the collimation onto
the acetate
Repeat with other cassette sizes (use different colours)
When x-raying a patient collimate so that you can just see the coloured line and this will then be
inside that film bounds.
*The reason for using sellotape to stick the acetate is that it can be removed if you do it wrong or if
the boss doesn’t like it (in which case keep it for your own use, but put a small mark on the
collimator housing and the acetate so that you can re-locate it accurately)