Shooting high ISO vs underexposing and lifting in post question

Started 3 months ago | Discussions thread
Slaginfected Contributing Member • Posts: 745
Re: Amplifying noise

JimKasson wrote:

If the bottom four or five bits are already noise, a left shift does no harm. In fact, if you've got 3 or 4 LSBs ( and some experiments say even less) of noise, increasing precision has no visible effect.

But the pushing is rendering the lower bits "empty" or fixed, i.e. noiseless. That is the problem.

For example, you may have 32 (2⁵) tonal steps with noise. If you shift that up 3 bits, you have 4 larger tonal steps left, and the noise is only addressing these 4 tonal steps, not the original 32 anymore. Posterization. So you have to fill these empty bits again with noise to return to the 32 tonal steps to get the effect you talk about. Alternatively, you can widen the data at the beginning and fill 3 or more bits of noise already, depending on the precision you need for the calculations. That is what I described.

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