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relative QE just gives the relationship between the QEs at various wavelengths - eg, it might show that the QE at Ha is 2/3 that at 500nm. It does not tell you what either one actually is - ie how many photoelectrons you will get for a given number of photons at that wavelength. To measure that you need a calibrated source and geometry that is known, so that you can say with confidence that the illumination on a pixel is nn photons and then by measuring the signal, you can work out the absolute quantum efficiency = photoelectrons/photons.
Forget the Sensorgen stuff - it is based on poorly documented measurements that may or not have anything at all to do with absolute quantum efficiency. For example, in one of primary the source documents, the author states "The calculated QE is denoted as relative QE, since there might be an multiplicative factor for all QEs. But my opinion is that the range 23 – 40% is quite true for CMOS sensors." uuurk!
The only way to measure absolute QE is with a calibrated light source and precise geometry.
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