* If I take an image at the shortest shutter speed I can and at a dark image, I see a nice Gaussian peak in RawDigger at 127, I do not see a 'spike' at 4095, even after I have underexposed this far. In other words, I am not seeing any 'hot pixels': my assumption being I would see these in the 4095 bin (but I could be wrong here?).
The above has told me that your count (the lapser-count), which is statistically down on the real count, ie you sample the real RAW data, means that if I use a 'zero threshold' or 10-200 (to account for bin width), I should be OK. In other words if I use a lapser-count in the righthand 1/3 stop of the righthand zone (2046 bins wide), I can use 10 or 20 as my threshold, ie this is my 'zero'. Indeed this is what I am finding.
Of course, each scene is different and speculars could throw my 'zero' test off.
BTW I still have not worked out how to put CHDK on a 8Gb card or larger without a lot of 'mucking about'.
I was trying to figure out what all the dots are in the dng images you posted. They may be "dead pixels", which apparently show up as totally black, i.e. 0. They might show up in my histogram as 0 pixels, but I probably am skipping over them since my sample step size is around 50 pixels for a full image.
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