Quantum Data 881 User Manual page 908

Purpose
Method
Bosch
Description
Appendix B Image Reference
880
The purity characteristics of your CRT can change over time if you leave it on with a lot of
video being displayed. This may be due to the CRT's electron beams striking its shadow
mask with enough energy to cause the mask to heat. This internal heating may be enough
to cause the shadow mask to warp and give bad purity.
Set the purity image to white and allow the monitor to run for a few minutes. Any mask
warping shows up as a change in purity. You can use a color meter to measure the
change. The BriteBox pattern may also be useful for measuring shadow mask warping.
Special test image developed per customer specifications. This image has 6 versions.