#reference/photography

Statistics & Stack groups

https://helpx.adobe.com/photoshop/using/image-stacks.html

Rendering plug-in name | Result | Comments

Entropy

Result : entropy = - sum( (probability of value) * log2( probability of value) ) : Probability of value = (number of occurrences of value) / (total number of non-transparent pixels)

The binary entropy (or zero order entropy) defines a lower bound on how many bits would be necessary to losslessly encode the information in a set.

Kurtosis

Result : kurtosis = ( sum( (value - mean)4 ) over non-transparent pixels ) / ( ( number of non-transparent pixels - 1 ) * (standard deviation)4 ).

A measure of peakedness or flatness compared to a normal distribution. The kurtosis for a standard normal distribution is 3.0. Kurtosis greater than 3 indicates a peaked distribution, and kurtosis less than 3 indicates a flat distribution (compared to a normal distribution).

Maximum

Result : The maximum channel values for all non-transparent pixels

Mean

Result : The mean channel values for all non-transparent pixels

Effective for noise reduction

Median

Result : The median channel values for all non-transparent pixels

Effective for noise reduction and removal of unwanted content from the image

Minimum

Result : The minimum channel values for all non-transparent pixels

Range

Result : Maximum minus the minimum of the non-transparent pixel values

Skewness

Result : skewness = (sum( (value - mean)3 ) over non-transparent pixels ) / ( ( number of non-transparent pixels - 1 ) * (standard deviation)3 )

Skewness is a measure of symmetry or asymmetry around the statistical mean

Standard Deviation

Result : standard deviation = Square Root(variance)

Summation

Result : The sum channel values for all non-transparent pixels

Variance

Result : variance = (sum( (value-mean)2 ) over non-transparent pixels ) / ( number of non-transparent pixels - 1)