If your pixels are so small or insensitive that some don't get a photon in a red flower petal that is illuminated, there will be no black speck; it will just "not" contribute at all to local luminance, as it probably shouldn't.
John,
That's quite right! An actual, totally 'black speck', as seen on the monitor, could only occur if all the 27 sub-pixel elements were switched off. (Remember, I'm talking about a 6 micron Foveon type pixel consisting of 9x2 micron Foveon sub-pixels. 27 photon collectors in total for each pixel seen on the monitor.)
The luminance range of the 6 micron Foveon pixel stretches from 'all 27 sub-pixels off' (black) to 'all 27 sub-pixels on' (white). The possible number of values in between these two extremes is given by 8 to the power of 9, ie 134m.
Clearly, it doesn't make any visible difference if a single sub-pixel is switched off when it should be switched on. The change in tonality of the 6 micron pixel would be altered so slightly, one wouldn't notice. But a few random sub-pixels, within the group of 27, that are in the wrong state, could make a visual difference.
If you give it enough thought, I think you will realize that there is no value in trying to outsmart shot noise. It will only lead to more noise. Shot noise is actually the very fabric of light. You can't figure out a better truth than what it is telling you; if you want less shot noise, relative to signal, get more signal. Don't fabricate it.
Maybe you are right. However, I haven't stated that shot noise will be distinguished from other types of noise in such a system. The purpose is to get as accurate a signal as possible. It makes no difference to the final result what the source of the noise is. Noise is noise whatever the source, ie.
inaccuracy.
In these examples of isolated sub-pixels which are in the wrong state, it seems to me, if I've understood the nature of shot noise, that shot noise will often be a contributing factor. Let's look at what I image happens to a sub-pixel in the 'cliff edge' situation. Noise (from all sources) is 50.1%; signal is 49.9%. The sub-pixel is switched off because the signal threshhold for switching the sub-pixel on, has not been reached. We don't actually
know that the signal is actually 49.9%. It doesn't really matter. The reality is, the sub-pixel is in a state of 'off' when it should be 'on'. How do we know it should be 'on'?
Because there's no reason for it to be 'off' (except noise) if it's surrounded by a cluster of sub-pixels which are on.Anyway, maybe this is a just a red herring and there's no need for an algorithm to make such decisions. My imaginary system is not founded on such a procedure. It simply occurred to me that
maybe this could be a method of tackling photonic noise. If there are too many errors due to insufficient light, then maybe nothing can be done except increase exposure.
So let's ignore this imaginary noise reduction system, which would take an enormous amount of processing power anyway, and concentrate on the fundamental principle of a 6 micron Foveon type pixel that gets its tonality from the on/off states of 27 sub-pixel photon collectors.
Any flaws in that idea?