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How are Mean, Median and Sigma Calculated for RGB Pixel Stacks ?


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Hi,

I've been experimenting with different stacking methods, and (finally) understand the algorithms behind Mean, Median and Sigma stacking.

My question relates to how the Mean / Median / SD is calculated for an RGB pixel stack.

Am I correct that, for each pixel stack :-

a. find the mean / median / Sigma for each of the R, G, B values separately, for each pixel stack; then

b. combine those RGB values to create a mean / median / SD RGB pixel ? 

In other words, are the R, G and B values each processed separately, or is some other metric (eg the L in an HSL model) used to determine the mean / median / Sigma ?

I hope that makes sense :)

Gary

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Hi Gary.

11 hours ago, Gary.JONES said:

In other words, are the R, G and B values each processed separately

Yes.

You can check this by generating 3 layers and filling them with some random RGB values.
Stack the layers, set the stack to Mean, Median or SD and check the values in the info panel.
Finally, do the math in a spreadsheet to compare the values with the info panel.

Here is an example:

stackx.png.56a99806b28f49d387297462f5ac5b8b.png

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