Re: Question about Lab and monitors....
Re: Question about Lab and monitors....
- Subject: Re: Question about Lab and monitors....
- From: Roger Breton <email@hidden>
- Date: Fri, 13 Feb 2004 09:01:52 -0500
>
With my Spectrolino and the Measure tool of Gretag (spot option) I measured
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the color of a flat image on Photoshop. The image was create in Lab (for
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example 54/81/70).
That color is barely within the bounds of my monitor according to
ColorPicker? It's likely clipped.
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The readout of spectrolino was 48.5/65.6/57.8.
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Ok, de DE94
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is 6.46. After that, with the ColorPicker I did the next test. I configured
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with the Icc of the Monitor in point... and insert the same Lab values like
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"lab input". The result was another different color (52/69/60 DE94 3.4)
Yes, how come there is a difference you say?
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What means that????
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a) The monitor is not properly calibrated.
No, it is not a function of calibration or profiling since Photoshop and
ColorPicker are both using the Destination profile to convert from Lab to
RGB and back to Lab to calculate DeltaE. Are they getting there differently?
That's a question for gretagmacbeth, for sure.
>
b) ColorPicker tool is not a god tool to predict.
No, try some other tool like ColorShop X and it should give you the same
result.
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d)the Icc is not god, because if not, the ColorPicker should give the measured
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lab (more or less)
Yes, the ICC is not god, and yes ColorPicker should give you the measured
Lab (more or less).
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e) The limitation of the CRTs allows these type of confusion...
True. There could be a variation between the time you calibrate and profile
and the time you re-meaasure in Photoshop. But that should not be a large
difference.
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f) Photosop fail with the lab colors...
What are you calibrating your display to: D50, D65 or what? Try calibrating
to D50 and repeat the same experiment and tell me if you see a difference.
As far as I know, if you calibrate to other than D50, Photoshop does not
manage the color 'absolutely' to the display, meaning it can't give you
what's called 'corresponding colors'. I'm interested to hear what others
have to say about this, especially the folks from Adobe (I could be utterly
confused about it myself even after years of reading and experimenting and
thinking about this problem) but this is getting to be a complex discussion
because, as far as I know, we're going to have to introduce the business of
chromatic adaptation into the equation. And if you really want to understand
the difference between the color you measure with your instrument, after
profiling, and the one predicted by your profile in ColorPicker, you are
going to have to take chromatic adaptation into account.
>
Xabier Urien
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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