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
(2) the optical low pass filter with his own MTF which is intended to minimize the
(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.