Automatic Image Processing in Digital Photoprinters

摘要

The conventional photographic system, based on AgX film and paper will be briefly described. There are many issues to be improved by digital image enhancement: at under exposed images the reduced contrast, color saturation and increased grain; cross curving of film and paper; the problems due to the limited contrast rendering ability of the paper with respect to the total dynamic range and the loss of definition at high saturated colors. Automatic scratch and dust removal and new products with manipulated color saturation (sepia, black & white) are examples for new possibilities due to digitization of the lab equipment. The digital workflow is also a prerequisite for the production of prints from digital cameras and to provide digital files from scanned film. This market will grow considerably in the near future and the photo industry has to make preparations for this development. But these images exhibit also artifacts like increased noise at under exposure or unbalanced density and color due to misled exposure control of the camera and limited dynamic range of the system. Although the image enhancement algorithms are well developed for professional applications, their utilization in high productive amateur labs is not simple since the cost performance relations are not acceptable. They lack of the necessary interaction by an operator. Automatic operation of the digital systems in a high productive lab will stay a challenge for the industry.