Originally posted by beholder3 Yes, that is what I explained above. And long exposure sensor heat up does
not create random noise. Stacking without DFS just removes random noise and keeps the heat induced static noise pretty much exactly as it is. The hot pixels do stay where they are on each shot. The average of ten shots which all show 255 or 16000 on one pixel is what? Zero?
Only you will see the heat noise much better because everything around it has been flattened by stacking but they remain shining as they did before.
That is why the Astro pros use dark frame subtraction.
It is extremely easy to understand if you think about what you are doing.
Ii is, the “new” thing for Pentax users is this new noise that is some form of semi stuck pixels that are not 255 or 0 (if we pretend the picture is 8 bit) they are somewhere in-between. I say semi-stuck as they are also heat dependent, or so it seems, and thus not always there.
And subtracting dark frames are NOT the super solution you seem to think. A hot pixel at 255 which are subtracted by a darkframe with the same value of 255 results in 0.
So the bright pixel is instead now a black pixel. That is fine if the surrounding pixels also are black, but that is not always the case. In camera dark frame subtraction patches this hole, but in camera dfs isn’t always practical.