28 November 2007 Optics for digital photography
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The role of optics in digital photography is in certain aspects quite different from that in conventional (silver-halide) photography. We first give an overview on the different classes of the digital still camera market. In order to judge the role of optics, one has to look on the different members of the transmission chain and their influence on image quality. These are mainly: (1) the optoelectronic image sensor with his modulation transfer function (MTF) and the particular situation of sensor cross-talk (aliasing), which will be interpreted as spatial frequency depending additive noise. A quantitative measure for this will be given. (2) the optical low pass filter with his own MTF which is intended to minimize the cross-talk (aliasing). (3) the optical system which has to be in a well balanced equilibrium concerning image quality with these components. Besides MTF-considerations the generation of colour has significant influence on image quality. Here the appearance of colour fringes is most disturbing and is due to different reasons. First of all the widely used (RGB) Bayer mosaic filter gives rise to colour aliasing because of the enlarged pixel pitch in the RGB-channels. Secondly the missing colour pixels in each channel must be interpolated from the corresponding neighbours who also introduce colour artefacts. Last but not least the optical system may contribute to colour fringes if the lateral chromatic aberrations are not corrected to a high degree.
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Karl Lenhardt, "Optics for digital photography", Proc. SPIE 6834, Optical Design and Testing III, 68340W (28 November 2007); doi: 10.1117/12.785073; https://doi.org/10.1117/12.785073


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