In cross-media colour reproduction, it is common goal achieving media-relative reproduction. From
the ICC specification, this often accomplished by linearly scaling XYZ data so that the media white of the
source data matches that of the destination data. However, in this approach the media black points are not
explicitly aligned.
To compensate this problem, it is common to apply a black point compensation (BPC) procedure to
improve the mapping of the black points. First, three lightness rescaling methods were chosen: linear,
sigmoidal and spline. CIECAM02 was also implemented in an approach of a lightness rescaling method;
simply, lightness values from results produced by CIECAM02 handle as if reproduced lightness values of an
output image. With a chosen image set, above five different methods were implemented. A paired-comparison
psychophysical experiment was performed to evaluate performances of the lightness rescaling
methods.
In most images, the Adobe's BPC, linear and Spline lightness rescaling methods are preferred over
the CIECAM02 and sigmoidal lightness rescaling methods. The confidence interval for the single image set
is ±0.36. With this confidence interval, it is difficult to conclude the Adobe BPC' method works better, but not
significantly so. However, for the overall results, as every single observation is independent to each other, the
result was presented with the confidence interval of ±0.0763. Based on the overall result, the Adobe's BPC
method performs best.
Where an illumination source includes flux in the UV region, an estimate of the total flux in the UV can be derived from
the fluorescent efficacy of a reference material and the fluorescent emission from the material. A correlate of fluorescent
efficiency was derived using a triangular weighting function in the fluorescent emission region and the flux in the
fluorescent excitation region. This was found to be constant at different flux intensities, and was used to estimate the UV
content of a test illumination. The method gave good results but requires further verification using other materials and
illumination intensities.
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