Camera calibration for colour vision research
Kobus Barnard and Brian Funt, "Camera calibration for colour vision research,"
Conference on Electronic Imaging, 1999 (to appear).
In this paper we introduce a new method for determining the relationship
between signal spectra and camera RGB which is required for many applications
in color. We work with the standard camera model, which assumes that the
response is linear. We also provide an example of how the fitting procedure
can be augmented to include fitting for a previously estimated non-linearity.
The basic idea of our method is to minimize squared error subject to linear
constraints, which enforce positivity and range of the result. It is also
possible to constrain the smoothness, but we have found that it is better
to add a regularization expression to the objective function to promote
smoothness. With this method, smoothness and error can be traded against
each other without being restricted by arbitrary bounds. The method is
easily implemented as it is an example of a quadratic programming problem,
for which there are many software solutions available. In this paper we
provide the results using this method and others to calibrate a Sony DXC-930
CCD color video camera. We find that the method gives low error, while
delivering sensors which are smooth and physically realizable. Thus we
find the method superior to methods which ignore any of these considerations.
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Keywords: colour, colour constancy, camera calibration
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