From DXOMark: More pixels offsets noise3

Started May 30, 2009 | Discussions thread
ejmartin Veteran Member • Posts: 6,274
Re: That is what I have seen also

DSPographer wrote:

ejmartin wrote:

What is the degree of correlation of the average of the masked pixels
in a given column/row with the average of the active pixels in that
same column/row? If it's over 50% won't you do better by subtracting
the masked pixel average from the active pixel data?

It is right about 50%. The first masked row has ramps rather than
black level and the second row is also contaminated. That leaves
about 50 masked rows but the masked rows don't all have the same mean
value as the dark frame image: only the last 9 rows match the image
black level. Using only those last nine rows the correlation
coefficient between the masked and unmasked means is about 0.46 but
using masked rows 3 through 52 raises the correlation to about a 0.54
coefficient. Unfortunately this is not really enough to make a
visible difference in the pattern noise. For comparison the
correlation between the mean of the rows in the top half of the
unmasked black image and the mean in the bottom half is about a 0.97

Thanks. BTW, what software are you using to get at the masked pixels?

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