CCD characterization for a range of color cameras

CCD cameras are widely used for remote sensing and image processing applications. However, most cameras are produced to create nice images, not to do accurate measurements. Post processing operations such as gamma adjustment and automatic gain control are incorporated in the camera. When a (CCD) camera is used as measurement instrument, it is important to have an accurate model of the imaging process and its noise. This model needs to be verified for the camera at hand and the model parameters should be estimated. Often however, a model is assumed and optimal performance is claimed without verification of the model. In this paper, we analyze a range of different types of cameras. We verify a general model of a CDD camera including post processing using experiments. It is shown that for a typical consumer webcam, the general model does not hold. The parameters of the model are estimated. It is shown that for most cameras the model can even be simplified under normal operating conditions by neglecting the dark current. We further show that the amount of additive noise is exceeded by the amount of multiplicative noise at intensity values larger than 10-30% of the intensity range