Hot pixel positions

[Guest]

I always thought that hot pixels stayed hot but looking through a number of darks I made the other day I see that the hot pixels are not always in the same place. Is that normal?

 

[vlaiv]

3 minutes ago, woodblock said:

I always thought that hot pixels stayed hot but looking through a number of darks I made the other day I see that the hot pixels are not always in the same place. Is that normal?

 

What camera is that?

Hot pixels stay hot for some period of time - like months. For this reason it is advisable to redo dark library once or twice a year.

If you have CMOS camera - what you are seeing might be Telegraph type noise. Mechanism is similar to dark current but reason is different. Electrons build up between pixels due to imperfections in substrate and then leak into pixel making it "hot" (high in value), but this does not happen on every exposure - hence then name Telegraph (think Morse code). Some camera models have these build up zones in between adjacent pixels and pixels "share" accumulation - so sub can have either one pixel turning "hot" - the other one turning "hot", or neither of the two - and this happens at random.

If you have this happen on a pixel - you'll get two or three pronged Gaussian distributions of that pixel values in series of your darks.