Re: Color difference equations [was: Color Measurement]
Re: Color difference equations [was: Color Measurement]
- Subject: Re: Color difference equations [was: Color Measurement]
- From: Steve Upton <email@hidden>
- Date: Thu, 16 Jul 2009 16:48:54 -0700
At 6:49 PM -0400 7/16/09, Terence Wyse wrote:
>On Jul 16, 2009, at 6:26 PM, Marc Levine wrote:
>
>>That being said, I believe that the application actually dictates which formula you SHOULD use...at least regarding elliptical (76) vs. non-elliptical (2000 and counting...)
>
>
>Or vica-versa, in reverse. IOW, you meant to say...."regarding NON-elliptical (76) vs. elliptical (2000 and counting...)"
>
>I think Marc's post sums it up quite nicely.....dE76 where instrumentation is concerned or any situation where variation, consistency, repeatability should be measured independent of an observer...but where VISUAL variation is concerned (i.e. comparing proofs to a standard reference), perhaps one of the perceptual/elliptical formulae should be considered.
Hi Terry
While I appreciate the point you and Marc made I don't see the overall value.
In conversations I've had with "lay people" customers about tolerancing, I find that they often ask about *when* they should care about variation. It seems like "caring" brings us right back to perception and dE2000 being a better match to perceptual differences than dE76.
While dE76 can be an effective process control tool, if we don't ensure that the differencing correlates to perception then we might as well be recommending good ol' density. Isn't the reason we want to use colorimetry in process control that we want to bring things closer to perception?
Then there's the issue of dE2000 doing a better job of "democratizing" the color space. Metrics and their tolerances (like Max dE) tend to be applied in the same way throughout the color space. But if dE in yellow is a very different commodity than dE in gray then Max dE becomes a color-dependent quantity which it is not supposed to be!
unless I'm missing something...
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
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