It's very easy to fake the test and then say - look, your screen is within tolerance: - provide a black & white pattern for 3 minutes - provide a gray pattern

It's very easy to fake the test and then say - look, your screen is within tolerance: - provide a black & white pattern for 3 minutes - provide a gray pattern _with compensation_ for the black&white for 1 minute If your gray compensation doesn't fall through the minute, you are within tolerance. If not, then the compensation was not enough and your screen is way off. Either way, your screen is toast. Since, by definition, only people with defective screens will waste time to go to service, only they will see the test and risk to see the compensation on a good screen.