[filmscanners] RE: Vuescan upper histogram

["michael shaffer" <rarewolf@roadrunner.nf.net>]

Ken writes ...

> ...  I think I understand that the bottom histogram in Vuescan
> is the RGB channels, but what is the upper one, and why does
> it not clip sometimes when the lower ones do?

  It is Ed's best calculation of the "lightness" of a pixel.  If I remember
correctly, it is weighted to the green channel value, and least weight goes
to blue ... I believe you can see a similarity.

  Weighted green is the most common method for evaluating lightness ...
however, since Vuescan's histogram is most commonly used for evaluating the
endpoints, black & white, I wonder if equal weighting is more appropriate(?)

cheerios ... shAf  :o)
Avalon Peninsula, Newfoundland

----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body