Re: Another quote from Roy Berns on metamerism-color inconstancy
Re: Another quote from Roy Berns on metamerism-color inconstancy
- Subject: Re: Another quote from Roy Berns on metamerism-color inconstancy
- From: Marco Ugolini <email@hidden>
- Date: Thu, 17 Jun 2010 14:56:02 -0700
- Thread-topic: Another quote from Roy Berns on metamerism-color inconstancy
In a message dated 6/17/10 1:56 PM, Ernst Dinkla wrote:
> Marco Ugolini schreef:
>> This is from the same book ("Billmeyer and Saltzman's Principles of Color
>> Technology", Third Edition, Wiley & Sons, 2000), on page 130:
>>
>> "[W]e want to stress that color inconstancy applies to a SINGLE SAMPLE
>> [author's emphasis -- MU] viewed under multiple illuminants. 'Metamerism'
>> should never be used when describing a single sample's change in color due
>> to changes in illumination. Metamerism always describes the color
>> relationship between a PAIR OF SAMPLES [author's emphasis -- MU], at
>> minimum."
>>
>> Like I said earlier, there's little to add to this one either. Couldn't be
>> clearer and more straightforward.
>>
>> But of course anyone is free to ignore it.
>>
>> Marco Ugolini
>
> A complex one then. Not two or more samples of the same color and not
> one sample either.
I don't follow. Is that what you read in the quote? I don't.
The quote DOES mention "a SINGLE SAMPLE viewed under multiple illuminants".
So, it's ONE The fact that we are dealing with one single sample/specimen IS
the whole point of the color inconstancy concept.
> A range of monochromes along the same hue angle on
> one page. Let us say a greyscale range. A neutral black and white print.
> Viewed under a continous spectrum D50 lightsource and doesn't show color
> shifts along the range and no tone fluctuations either. Goes wrong under
> a bad CFL lamp, green in the highlights, bluish halfway, red shift
> towards black. There is a reference as we expect a neutral grey or at
> least a continuous hue along that tone range, no hue differences, no
> saturation differences. Only the grey value variation. In fact some
> metamerism tests are made that way, black and white line grid grey next
> to for example a composite mix grey. Right, the samples have the same
> grey value then when it gives the metameric match. Nevertheless there's
> a good reason why we discriminate the shifts in B&W prints where it
> wouldn't be as easy in color prints. This comes close to a metameric
> match or failure in my opinion.
"Close"? So Berns is incorrect in saying that "'[m]etamerism' should NEVER
[my emphasis -- MU] be used when describing a single sample's change in
color due to changes in illumination"? Better write to him so that he will
stand corrected -- quick!
Roy S. Berns <email@hidden>
> A good friend, artist in his early years, made (40 years ago) some
> landscape paintings from sketches where the tone values and saturation
> where kept equal in all patches, only the hues varied. Munsell color
> system book next to the easel. I recall the gouache paint was mixed
> under a fluorescent lamp, probably the Philips 95 then, in best case. I
> don't think we ever discussed metamerism [...]
Still insisting on calling it "metamerism"? After all this? Excuse me for
feeling frustrated...
Marco Ugolini
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