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Hi Jens,
> Yes, but in the case that the read-noise increases with a longer
> exposure time (and the brighter images were captured with longer
> exposures), it would maybe pointing to a wrong darklevel acquisition.
Agreed. But in this setup, the integration time was held constant and
the exposure time (the time the light source was on) was increased to
get more signal. So, the dark level should be pretty consistent.
> > I would expect the characteristic steep fall off of the curve at
> > saturation.
>
> Yes, if the converter is saturating bevor the sensor gets close
> to the fullwell.
> Otherwise it shouldnt fall off so quick, dependend on the sensors
> characteristic. Ok, 760e noise_rms is nothing against 500ke fullwell,
> so it wouldnt flatten the curve a lot, too.
So if I'm at full well and the convertor isn't saturating, the curve
still won't drop off quickly?
--------
If I can go back to something you mentioned earlier about non-linear
response: you mentioned that non-linear pixel response (output voltage
/ incident photon) could also affect the photon transfer curve. Well,
I found an interesting article that describes this in detail. In fact,
they derive a method to determine things like conversion gain of a
non-linear sensor that appears to be quite accurate. Maybe it is of
some interest to you:
Bedabrata Pain and Bruce R. Hancock, "Accurate estimation of
conversion gain and quantum efficiency in CMOS imagers", Proc. SPIE --
Volume 5017, pp. 94-103, 2003
As always, Thanks.
-Patrick
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