We must analyse the issue in both side of the coin.
1) the main noise in lights is reduced by amount of these lights. The noise isn't created by the camera.
2) there are others electronic noises:
a) in light, dark, flat and bias
b) hot pixels
3) DSS can subtract these electronic noises and clean the image, enabling enhancement of details in photo. But these files will carry electronic noise, too.
And it will be the same for lights. The amount of files can reduce these noises.
I will experiment with much more bias files and stack then again to see the difference in the result. I will post it here. I used only 10 bias files. (How many bias files I will need with my set of equipments and my Canons T3 - 350D ?
)
Some very important texts from DSS documentation about the matter:
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Following the square root rule you will have much cleaner masters if you use a lot of frames to create them. Remember that you are trying to remove the dark and bias signals, not the noise that is coming with it.
For example when you subtract the master dark from each light frame you are adding the noise of the master dark to the noise of the light frame. The smaller the noise of the master dark, the less noise you will add to the light frame. This is also true for the master bias and the master flat.
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In fact by using only a very small number of frames for the creation of the masters you can easily triple the noise of the calibrated light frame (bias and dark subtracted and flat divided) compared to the noise of the light frame before calibration.
You will then need 9 times (3 squared) more light frames to bring back the noise to the level you could have had by using noise free masters.
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Hot pixels are pixels that are not behaving normally. They are a very strong signal that is visible in each dark and each light frame.
Of course when you subtract (only) one dark frame to one light frame you will remove the hot pixels which may give the false impression that the dark subtraction did its job.
However, at the same time the subtraction doubled the noise of the calibrated light frame and ruined it thoroughly.
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