0000000000484177
AUTHOR
Francisco M. Martínez-verdú
Characterization of a digital camera as an absolute tristimulus colorimeter
An algorithm is proposed for the spectral and colorimetric characterization of digital still cameras (DSC) which allows them to be used as tele-colorimeters with CIE-XYZ color output, in cd/m2. The spectral characterization consists in the calculation of the color-matching functions from the previously measured spectral sensitivities. The colorimetric characterization consists in trans- forming the raw RGB digital data into absolute tristimulus values CIE-XYZ (in cd/m2) under variable and unknown spectroradiometric conditions. Thus, in the first stage, a gray balance was applied over the raw RGB digital data to convert them into RGB relative colorimetric values. In the second stage, an algo…
Analyzing the metrics of the perceptual space in a new multistage physiological colour vision model
In this work, the metric of a new multistage colour vision model, ATTD05, is assessed and a new colour difference formula is suggested. Firstly, the uniformity of the ATTD05 colour space was compared with that of CIECAM02 for some Munsell samples, because if the model yields a uniform perceptual space, we will be able to implement a colour difference formula as a Euclidian distance between two points. Secondly, we developed a new space based on the perceptual descriptors of the model: brightness, hue, colourfulness, and saturation. After that, we calculated the free parameters of the space that better fit the measured and experimental data of two datasets (small-magnitude and large-magnitud…
Application of the S-CIELAB color model to processed and calibrated images with a colorimetric dithering method.
This work uses the S-CIELAB color model to compare images that have been calibrated and processed using a colorimetric dithering method which simulates increments in viewing distance. Firstly, we obtain XYZ calibrated images by applying the appropriate color transformations to the original images. These transformations depend on whether the image is viewed on a display device or encoded by a capture device, for example. Secondly, we use a colorimetric dithering method consisting of a partitive additive mixing of XYZ tristimulus values. The number of dithered pixels depends on simulated viewing distance. The dithered tristimulus values are transformed to digital data to observe the dithering…
Review of the chromatic subjects about image capture (II)
Este trabajo aborda la problemática general de la reproducción del color que se genera en dispositivos de captura (escáneres y cámaras). Se expuso en la primera parte de este trabajo que los dispositivos de captura no son directamente instrumentos de medida del color debido a la opción tecnológica sistemáticamente usada en el diseño de sus sensibilidades espectrales. Por tanto, se estudian en esta segunda sección las opciones posibles de transformación de color o perfil colorimétrico entre el espacio RGB dependiente de estos dispositivos y el espacio estándar CIE-1931 XYZ. Esto conlleva a su vez una revisión de los algoritmos existentes para evaluar el grado de exactitud colorimétrica conse…
Concerning the calculation of the color gamut in a digital camera
Several methods to determine the color gamut of any digital camera are shown. Since an input device is additive, its color triangle was obtained from their spectral sensitivities and it was compared with the theoretical sensors of Ives-Abney-Yule and MacAdam. On the other hand, the RGB digital data of the optimal or MacAdam colors were simulated to transform them into XYZ data according to the colorimetric profile of the digital camera. From this, the MacAdam limits associated to the digital camera are compared with the corresponding ones of the CIE-1931 XYZ standard observer, resulting that our color device has much smaller MacAdam loci than those of the colorimetric standard observer. Tak…