GIMP Version: 2.8.10
Operating System: Linux
OS Version: Ubuntu 14.04 LTS
GIMP Experience: Beginner Level

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Desaturation has three options - Lightness, Luminosity, and Average.
I can see that they produce slightly different results.
Could someone explain the difference for a, not very bright, new boy?

david.

Lightness
The graylevel will be calculated as, Lightness = ½ × (max(R,G,B) + min(R,G,B)
Luminosity
The graylevel will be calculated as, Luminosity = 0.21 × R + 0.72 × G + 0.07 × B
Average
The graylevel will be calculated as, Average Brightness = (R + G + B) ÷ 3

This only works on layers of RGB images. If the image is in Grayscale or Indexed, it does nothing.

Many thanks for a lightning fast reply!

david.

Okay David.

If you need a more visual explanation, this might help as well (though Wallace pretty much summed it all up nicely):

http://pixls.us/articles/digital-black- ... rate-gimp-

patdavid,

As you say, Wallace summed it up nicely. However, the reference you gave me was fascinating. I have read it once quickly, but I think my "homework" will be to read it several times and think about the implications of the many ways to convert to greyscale.

Many thanks,
david.