SO... getting back to POV-Ray's built-in gamma set-up chart...

As that chart was made many eons ago, I had a desire to see if it is still
'accurate' in the modern world ;-)  Leaving no stone unturned, I copied that
image and took it into both my (older) Photoshop, and a recent version of GIMP--
 to check not the thin horizontal bars, but the gray 'gamma' swatches that they
are compared against.  (BTW, both of my apps are working in sRGB color/gamma
space.) Using the 'eyedropper' tools there, I measured the gamma 2.2 swatch. Its
brightness value in both apps reads as 186/255, or 0.72941    And 0.72941^2.2 =
0.49950, or almost exactly 0.5

I can't say that I know exactly what I'm doing with this experiment-- ha!-- but
is  0.72941  the correct value for the gamma 2.2 swatch? (I assume it is, of
course, but I wanted an expert's opinion.)

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