Shot Noise - A question for the wise ...

Started Jul 21, 2012 | Discussions thread
Steen Bay
Veteran MemberPosts: 6,188
Re: Shot Noise - A question for the wise ...
In reply to Detail Man, Jul 21, 2012

Detail Man wrote:

bobn2 wrote:

Detail Man wrote:

Question : If what is often referred to as "photon shot noise" in photo-detectors is, in fact, only a property of the light that is allowed to illuminate the surface of the photo-detector - and not to some extent semiconductor shot noise generated within the photo-detectors themselves , then how and why is it said that a higher "quantum effieciency" results in lower levels of "photon shot noise" for a given level of light being transduced to electron charges ? Something does not add up

In the case of photon detection, the relevant process is the random conversion of photons into photo-electrons for instance, thus leading to a larger effective shot noise level when using a detector with a quantum efficiency below unity .

It's not only a property of the light. The photon shot noise depends on the number of photons counted, so it depends on the pattern in which photons present themselves to be counted (a property of the light) and the efficiency of the camera in counting them (a property of the camera).

Yet, it seems that a full 14.8% improvement in an image-sensor's quantum efficiency will result in what seems like an essentially insignificant improvement in photon-shot-noise related SNR (0.1 EV).

Doubling the QE will 'only' increase the SNR by 41%, so guess you could say that a small improvement in QE only will result in an "essentially insignificant" improvement in SNR. I'd prefer to say that a 41% increase in SNR is a 'one stop improvement', since it'll mean that the camera now will have the same noise at iso200 as it had at iso100 before, but guess that's open for discussion.

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