HDR Photography

Camera calibration can be divided into three aspects: geometric calibration, photometric calibration and spectral calibration. For HDR reconstruction, the important aspects are photometric and spectral calibrations.
• Color reproduction
Light sensors and emitters try to mimic a scene's light signal concerning human perception; it is the human perception that is important concerning colors reproduction. Inspired on the trichromatic base of the human eye, the standard solution adopted by industry is to use red, green, and blue filters, referred as RGB base, to sample the input light signal and also to reproduce the signal using light-based image emitters. This employs an additive color model, as opposed to the subtractive color model used with printers, paintings etc.
Photographic color films usually have three layers of emulsion, each with a different spectral curve, sensitive to red, green, and blue light, respectively. The RGB spectral response of the film is characterized by spectral sensitivity and spectral dye density curves.