Re: How to get the DE 94
Re: How to get the DE 94
- Subject: Re: How to get the DE 94
- From: "Steve Lawrence" <email@hidden>
- Date: Wed, 22 Oct 2003 20:21:04 +0100
- Thread-topic: How to get the DE 94
Peter wrote:
>
I think there is no "correct" factor for CIE94, because those
>
factors should be used to get a better fit for specific
>
applications. _But_ I also would welcome one or a set of
>
"suggested factors" for typical applications. Right now it's
>
not possible to compare DeltaE94 values, while DeltaE CIELAB
>
values are comparable of course. I hope that a consense is
>
found in the near future, so we can use the often better
>
"fitting" DeltaE94 values or a successor of them.
>
>
If someone knows a reference to a standard factor I'd
>
appriciate to hear that very much too.
>
The "k" coefficients are all 1 for the CIE reference conditions. The
latter being two side by side samples, placed on a uniform, neutral
background of L*=50, illuminated by D65 with an luminance of 1000 lux
and viewed at a distance so that the pair subtends a visual angle of at
least 4 degrees. It's assumed a perceptibility, rather than
acceptability judgement is required. That is to say, "can I see a
difference?", rather than "is the difference acceptable?".
Credit where credit's due dept: All of the above from the excellent
colour science reference, "Principles of Color Technology", written by
(Dr) Roy S. Berns. I can't recommend it highly enough for anyone
interested in colour science. To my mind it is more readable and fills
in more of the background, than some of the other standard texts.
Dr Hunt's, "Measuring Colour", states that the coefficients are all 1
for most applications, whilst kl is 2 for the textile industry. Berns
contains numerous references to their development if you want to know
more.
As such coefficients are typically set within industries (to accommodate
their differing needs), it is probably safe to assume you can compare
different values, at least within the same industry. Put another way,
it's perhaps unlikely that GretagMacbeth and X-Rite say, are using
different coefficients to calculate the values in say, the graphic arts.
Although of course I'll now be proved wrong <g>. I applaud your rigour,
but such factors are a feature of all the "modern" colour difference
formula's for reasons well described in Berns. I would personally
encourage you to embrace the modern colour difference formula of your
choice. The benefits, far outweigh the negatives in my opinion.
Jeez..sorry for the long windiness.
Steve Lawrence
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