|
In camera noise reduction has a couple of other problems. I'll quote from MaximDL as it sums it up very well -
"Dark subtraction does not work as well when the images have already been converted to color."
"Unfortunately, and perhaps counterintuitively, subtracting a dark frame also adds noise to the image. Every pixel has random read noise, plus the residual dark current noise. This noise does not subtract, but rather adds in a root-sum-square fashion. Therefore simply subtracting one dark frame increases the noise level 41%. The way to get rid of this noise is to average it out of the dark frame by averaging. Every time you quadruple the number of averaged frames, you drop the noise contribution by half."
Mark.
|