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Our laboratory has investigated the efficacy of a suite of color calibration and monitor profiling
packages which employ a variety of color measurement sensors. Each of the methods computes
gamma correction tables for the red, green and blue color channels of a monitor that attempt to: a)
match a desired luminance range and tone reproduction curve; and b) maintain a target neutral point
across the range of grey values.
All of the methods examined here produce International Color Consortium (ICC) profiles that
describe the color rendering capabilities of the monitor after calibration. Color profiles incorporate a
transfer matrix that establishes the relationship between RGB driving levels and the International
Commission on Illumination (CIE) XYZ (tristimulus) values of the resulting on-screen color; the
matrix is developed by displaying color patches of known RGB values on the monitor and
measuring the tristimulus values with a sensor. The number and chromatic distribution of color
patches varies across methods and is usually not under user control.
In this work we examine the effect of employing differing calibration and profiling methods on
rendition of color images. A series of color patches encoded in sRGB color space were presented on
the monitor using color-management software that utilized the ICC profile produced by each
method. The patches were displayed on the calibrated monitor and measured with a Minolta CS200
colorimeter. Differences in intended and achieved luminance and chromaticity were computed using
the CIE DE2000 color-difference metric, in which a value of ΔE = 1 is generally considered to be
approximately one just noticeable difference (JND) in color. We observed between one and 17
JND's for individual colors, depending on calibration method and target.
As an extension of this fundamental work1, we further improved our calibration method by defining
concrete calibration parameters for the display, using the NEC wide gamut puck, and making sure
that those calibration parameters did conform, with the help of a state of the art Spectroradiometer,
PR670. As a result of this addition of the PR670, and also an in-house developed method of
profiling and characterization, it appears that there was much improvement in ΔE, the color
difference.
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