Development of a perceptual colorimeter based on a conventional CCD camera with more than three color channels

In order to improve the precision of colorimeters based on a digital image capture device, we increased the number of acquisition channels by using a supplementary filter placed in front of the color camera and taking two images of the scene: one without the filter (3 RGB channels) and one with the filter (3 different UVW channels). We selected a wide-band cyan filter that increases the transmission of spectral zones common to the three pseudo-color matching functions of the CCD camera and the spectral transmission of the channel with the lowest sensitivity. This six-channel color measurement instrument shows an improvement in the precision level compared with a conventional three-channel system, obtaining a better Vora factor (greater than 0.96), color quality factor (greater than 0.95) and color reproduction index (greater than 96%). From the colorimetric values obtained with the six-channel system we developed a perceptual colorimeter by applying different color appearance models (ATD, Hunt’91, CIELAB, LLAB, Hunt’94 and CIECAM02). The results obtained with the colorimeter developed showed a good performance for the perceptual parameters in comparison with a conventional telespectroradiometer, especially when Hunt’94 and CIECAM02 models were applied.