yes its the filter dyes that give the spectral curves.
heres a D70s spectral response I did on a bentham monochromator late last year and one from Image Engineering.
Mine is scaled to unity but you can see the "bumps" are in the right place.
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BTW, are you sure that it's the filter dyes that give the spectral curves? They should be only one factor. I would have thought the response is the product of the transmissivity of the IR filter, the CFA color filter, and the response of the silicon. Granted all color channels would be the same without the CFA, but the response curve would not be flat.
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Papa,
The sophistication of your measurements indicates that you are a high level color person, but your statement that the filter dyes determine the spectral response puzzles me. I'm no expert, but Emil's explanation seems more likely. Without any filters, all the channels would be the same but the response curve would not be linear across the wavelength spectrum.
The spectral response of a typical CCD is shown [a href=\"http://www.andor.com/learn/digital_cameras/?docid=315]here.[/url] To create an electron, the photon must reach the depletion layer of the chip. Below about 350 nm, photons are absorbed by the gate structures (the silicon has a low transmittance at this wavelength) or reflected. As the wavelength lengthens, more photons reach the depletion layer and produce electrons. In the example, response is greatest at about 600 nm (yellow-red). In the far infrared region, photons can pass through the depletion layer and not be detected.
Similar explanation and a nice Java Tutorial is presented on the
Olympus Microscopy Site.In the case of the D70 chip, the Stanford SRF was obtained with the CFA and IR filters in place. Papa's SRF is similar, but shows relatively more response at about 625 nm.
The output of the pixel is dependent on the photons reaching the depletion layer of the chip and the spectral response of the silicon, which varies markedly with wavelength. The filters shape the response by limiting what wavelengths fall on the pixel, but the spectral response of the silicon plays an important role.
Since the SRF is obtained by observation of an intact camera sensor, there is no way to determine the individual contributions of the filters or silicon other than by a controlled experiment where the responses are determined individually.
Bill