Before we go further, I thought you might like to see how a modded 20D, with only clear glass over the sensor, behaves spectrally. The above shows a plot of the R, G, B pixels when exposed to a Solar spectrum. The Raw was Linear-Converted, with NO white balance. When Daylight White Balance is used in a stock, unmodded, camera the response comes out with 3 similar-height peaks. In a modded camera the Red demonstrates that the Canon CMOS sensors have a native response that peaks well into the Red. NB: H-alpha is at 6563 Angstroms and yes, there is indeed a dark line visible at that wavelength.