Re: Color Measurement
Re: Color Measurement
- Subject: Re: Color Measurement
- From: "Fleisher, Ken" <email@hidden>
- Date: Wed, 15 Jul 2009 16:52:37 -0400
- Thread-topic: Color Measurement
On 7/15/09 4:34 PM, "Richard Baguley" <email@hidden> wrote:
> Really? I though that the JND for both was around 1, but that dE 2000
> made adjustments for the sensitivity of the human eye at different
> fequencies?
This is not correct. The JND is just as Robin Meyers described it. The
difference with dE 2000 and the original dE 1976 is that the former attempts
to make the color space of the latter more visually uniform. In other words,
in dE 1976, dE 3 would mean a different amount of perceived change depending
on which color is being viewed. This is because the L*a*b* color space is
visually non-uniform, or said another way it is not a Euclidean space. DE
2000 attempts to correct this problem and is a great improvement, but is
still not a perfect solution. One unfortunate aspect of dE 2000 is that it
was scaled differently and produces smaller numbers than dE 1976 which is
why the JND is a smaller number.
(although, of course there is no precise definition of what
> JND really means...)
Why do you think that? Of course there is a precise definition for JND. From
Weber¹s Law of Just Noticeable Difference, a JND is the ³smallest detectable
difference between a starting and secondary level of a particular sensory
stimulus.²
--
Ken Fleisher
Photographer
Imaging & Visual Services
National Gallery of Art
Washington, D.C.
Phone: (202) 712-7471
email@hidden
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