A Color Model for Digital Photo Printing on Silver Halide Paper
Negative film is an important input channel for most digital minilabs, such as MasterflexD or Cyra system from Gretag Imaging AG. Typically, a negative film is scanned and digitized. A color-matching algorithm generates normalized, film-independent, and mask-corrected film densities (e.g. EyeTech). As opposed to analogue laboratories the exposing unit of a digital photo printer does not expose paper through negative film. Instead, normalized film densities are converted to CIELAB colors of an ideal paper using a spectral paper model. From the ‘device-independent’ CIELAB color space the image is mapped to the appropriate output device. In MasterflexD and Cyrafastprint a common output device is the digital photo-printer using DMD technology. The assumption of an ideal paper prevents us from restricting the gamut of the ‘device-independent’ CIELAB color space to a particular paper brand. The out-of-gamut areas between the ‘device-independent’ color space, the final print, and the sRGB monitor are kept small to minimize losses in image quality during gamut mapping.
The color model is also useful at the output. For output profiling classical color management tools use measured tristimuli from a large set of colored patches to probe the gamut and to relate CIELAB color values to the corresponding printer RGB values. A spectral model helps drastically reduce the number of required colored patches. In addition, a spectral model facilitates the description of the gamut boundaries compared to a purely empirical, grid-interpolating method.
Document Type: Research Article
Publication date: January 1, 2002
Started in 2002 and merged with the Color and Imaging Conference (CIC) in 2014, CGIV covered a wide range of topics related to colour and visual information, including color science, computational color, color in computer graphics, color reproduction, volor vision/psychophysics, color image quality, color image processing, and multispectral color science. Drawing papers from researchers, scientists, and engineers worldwide, DGIV offered attendees a unique experience to share with colleagues in industry and academic, and on national and international standards committees. Held every year in Europe, DGIV papers were more academic in their focus and had high student participation rates.
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