Last night I did a 40 seconds exposure indoor with NR enabled. I still got about 20 hot pixels. About 5 of them are bright blue. The rest are faint. Is this normal? Has anyone else tried this? I thought NR is supposed to eliminate all hot pixels. Help me out on this please.
My first question is whether they're really hot pixels. If they're really hot, multiple shots should show the same 20 pixels hot. At 40 seconds, you will get a lot of thermal noise as well, which cannot be cancelled by NR because it's random.
Here's the deal: Fixed pattern dark noise can be removed by subtracting a dark frame from an exposed frame. There is also random thermal noise that's different for each exposure. NR cancels out the fixed pattern noise, but it makes the random noise 40% worse. That's just the laws of physics for you.
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