Dr. Chan,
Please pass on the following query to CVNet. Thank you!
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I'd appreciate any reference pointers or immediate answers to the following.
An observer views a small spot, in both chromatic and lightness contrast,
against some "uniform" background, under photopic conditions. The spot is
distant (so depth cueing not a factor), and its diameter subtends anywhere
from 5-25 arcminutes.
My question is how to determine the joint color/lightness contrast
perceptibility threshold (Ct).
There's plenty of classical luminance-only experiments applying to just
such situations, which suggests a Weber Law form Ct of about 0.03
(near-foveal), for spots greater than 10 arcminutes (i.e., at the crossing
between constant-flux and constant-luminance size regimes). But what about
for color AND brightness?
In my ignorance, I'm tempted to employ a color difference metric, e.g., CMC
or CIE94, and scale it accordingly against an achromatic Ct of 0.03.
However, I wonder, at such spatial scales here, if color segregation is
occurring near contrast threshold. Is this approach appropriate? Is there
something better, most particularly relevant experimental data?
Thank you!
Frank J. Iannarilli, Jr. franki@aerodyne.com
Aerodyne Research, Inc., 45 Manning Rd., Billerica, MA 01821 USA