Re: Neutral grey under different lighting
Re: Neutral grey under different lighting
- Subject: Re: Neutral grey under different lighting
- From: Marco Ugolini <email@hidden>
- Date: Mon, 03 Sep 2007 21:03:41 -0700
- Thread-topic: Neutral grey under different lighting
In a message dated 9/3/07 11:53 AM, Roger Breton wrote:
> Marco, Ray, Martin and others,
>
> Just to drive the point home, for myself and possibly others.
>
> In Markus's case, since he's not comparing the appearance of two colored
> objects (a photographic prints and some other colored surface) across
> various light sources, this effect cannot belong to a class of visual
> phenomenon called "metamerism", right?
Hi Roger.
Right, I would say so.
> Again, in Markus's case, since he's comparing the change in appearance of a
> single colored object (his photographic print) viewed under various light
> sources, this effect properly belongs to a class of phenomenon called color
> inconstancy, right?
Agreed.
You have the ProfileMaker 5 application suite, right? In that application,
they refer to "color inconstancy" as "tone stability". In MeasureTool,
launch the "Comparing" function, then click on the "Tone Stability" radio
button. Load a set of spectral readings taken from a testchart. (Remember:
the Tone Stability feature only works with spectral data.) Then choose the
Observer Angle (2° is the default, which is good in most cases), then two
different illuminants, say D50 and A (tungsten). MeasureTool will use the
DeltaE formula of your choice to calculate the difference between the colors
produced by the interaction of each of the two illuminants with the spectra
in the measured samples.
Marco Ugolini
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