I’ve been told many times that you cannot use spectrophotometer measures of color difference (dE) to show the difference between offset raster color prints. Also, how wrong is it to actually use these measures? I’ve asked why a lot, no one seemed to know the answer.
In: Technology
Because you’d be trying to measure a load of little coloured dots so, at best, you’d get an average of what was visible in your sample window.
You’d also find that average changing quite a lot just by moving your sample window slightly.
So basically it wouldn’t tell you anything about any of the colours in your sample. You need a patch of flat colour larger than your sample window to get an accurate or useful reading.