Analysis Measurement Gray Values Incorrect?

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i'm trying use image analysis functionality of ps cs6 obtain brightness levels image.

 

to test "gray value" measurment, i've created 11 patches 0%-100% in 10% increments. used fill tool (shift-f5) , specified values using h=0, s=0, b=<percentage_value (0-100)>.

 

the respective rgb components of generated patches expected (255*percentage_value).

 

the measurements obtained through "record measurement", however, not agree, exception of 0% , 100% extremes, reported 0 , 255, respectively.

 

inbetween, there disagreement rises 0 @ 0% highest (5 @ 50%) decrease again 0 @ 100%.

 

here series reported gray values low (from 0% - 100%): 0, 3, 3, 4 4, 5, 3, 3, 2, 1, 0.

 

how come?

 

i've tried removing colour profiles (to exclude gamma encoding issues) , using different colour spaces and/or models, no change in behaviour.

 

all patches pure gray there shouldn't problem unexpected colour weighting.

 

one funny observation i've made though patches 100% homogenous, ps reports different miminum , maximum values. instance 50% brightness patch (rgb triples of 128, 128, 128), report minval=123, maxval=124, meanval=123.934809.

 

clearly, value 3 aspects should same, , expect value 128.

 

what missing?

 

i'm using ps cs6, version: 13.0.1 (13.0.1 20120808.r.519 2012/08/08:21:00:00) x32, on win 7.

40+ views , no reply?

 

please enlighten me.



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