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p.1 #5 · p.1 #5 · Multiple short exposures stacked = 1 long exposure without noise? | |
We have three noise sources in long exposures, photon shot noise, read noise and thermal noise.
Photon shot noise is the easiest here. It will only depend on the total accumulated exposure, and not depend on how you do it, one or multiple exposures. Since we use low ISO it will be very low anyway.
Read noise will add up for every new exposure. Read noise will show up in the deepest shadows. If you don't require very large dynamic range, this may not be significant.
Thermal noise is the noise that get annoying with long exposures. This will add up with the total exposure time, and thus not be any different from taking one exposure.
This is assuming that you use the ND filter when taking multiple exposures.
If you remove the ND filter, and the take multiple exposures that all capture more light, there will be a large benefit in stacking multiple exposures. The noise will be averaged instead of added, thus ending up lower.
The reason we don't always do it ,in addition to the extra work in post processing, is because there will be a delay between the exposure that may be visible in some types of movements, like light trails.
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