I tried and failed to find a spectral response curve for any M-Monochrom sensor today, even though it is said that Leica has published one.
Anybody got a link or have a copy please?
Elsewhere, a non-technical person is telling me that the sensor “measures luminance” which I find very hard to believe.
Not sure if this is of any use??
Thank you Todd, just what I was looking for !!
you da man …
What else would it do? Rather simplistically, a digital sensor is a photon counting device.
Photon not luminince.
In response to your rather condescending question:
Any device which measures luminance must have a spectral response that conforms to the CIE luminous efficacy curve. The Monochrom does not, although the curve does imply a built-in IR blocking filter which very roughly approximates the CIE curve in the green/orange/reds but certainly not at the blue end.
For example, I took the type 246 curve and superimposed an approximate luminous efficacy curve:
It is obvious from the responses at say 430nm wavelength that the type 246 violet-blue response is grossly in excess of the luminous efficacy curve and therefore that violet-blue wavelengths would be rendered far too bright with respect to green.
T4040SpecResp.pdf (414.0 KB)
I saw this figure one time. I was trying to figure it out (no pun intended). I took the lines to be theoretical, ie 100% was the perfect efficiency of photon capture I guess for a given FF?? Then incremented to show 10% decline and then the spectral curves were shown against these for reference??
Ignoring QE for now, it looks like the curves for a given sensor with an RGB Bayer CFA and also in black for no CFA and no UV/IR blocker. Very useful, thanks.
Silicon has a spectral sensitivity of its own. After that, it depends on the combination of filters applied on top of it.
Agreed.
