DeltaE and some complications - AVS Forum
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post #1 of 4 Old 04-16-2014, 08:35 AM - Thread Starter
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I was thinking about 2 hypothetical pairs of identical DeltaE errors, and I pickup an example about which I'd like to hear from you expert colortists...

Think about two near grey levels, say 40% and 50%. Now choose 2 pairs of such greys, with all 4 greys with a DeltaE of say...2.5. But with one crucial difference: the first pair of greys have errors with the same hue, while the second with an opposite hue.

Now if we happen to evaluate the quality of this 2 "calibrations" using DeltaE, we should affirm that they are of the same "quality", because trivially both exhibit an average DeltaE of 2.5

But unfortunately if we watch a greyscale steps, first time with the grey pair of the same hue, and then with the other pair containing grey of opposite hues, we would end up saying that the first calibration is better, since we can't perceive or recognise different hues in the grey steps.

The issue is that this obvious difference would not be factoried in by any average DeltaE measures commonly used here. So a sort of measure of the continuity in hues should also be taken into account...

Am I wrong? What do you think?
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post #2 of 4 Old 04-16-2014, 11:11 AM
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This is a good question. It's important to remember that delta E is a measure of how perceptibly different a standard is from a sample. There are many other factors that contribute to the overall color quality of any given presentation, and you've illustrated one particular example.

The book I'm reading now has a chapter that I think deals with this issue, and I'm looking forward to learning more about it.
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post #3 of 4 Old 04-16-2014, 12:14 PM
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One of the new features in CalMAN 5.3.5 is something we are calling Grayscale Tint Reduction.

Now during the AutoCal process we look not only at the dE to D65, but also the dE to it's neighbors. We then will only move on to the next calibration target when we've minimized the error for both values.
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Joel Barsotti
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post #4 of 4 Old 04-23-2014, 07:50 AM - Thread Starter
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Thanks for your replies! Actually the Calman approach here described by sotti may really give a plus!
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