  In this paper, we introduce a novel - physico-chemical - approach for
calibration of a digital camera chip. This approach utilizes results of
measurement of incident light spectra of calibration films of different levels
of gray for construction of calibration curve (number of incident photons vs.
image pixel intensity) for each camera pixel. We show spectral characteristics
of such corrected digital raw image files (a primary camera signal) and
demonstrate their suitability for next image processing and analysis.
