I'm so confused
Regarding Graft's hue filter. The saturation setting does the following. Setting it to
one leaves the rgb clip untouched, and setting it to
zero sets the rgb clip to (r,g,b)=(y,y,y) where y is the luminance (as in yuv). In [0,1] it just performs a linear interpolation (and linear extrapolation outside [0,1]).
Normally we have y = 0.299*r + 0.587*g + 0.114*b, but they use a gamma-corrected version: y = 0.3086*r + 0.6094*g + 0.0820*b (don't know yet where these numbers are coming from ...).
http://www.sgi.com/misc/grafica/matrix/index.html
What I don't understand is, how is this related to the saturation in the hsv color format? I guess there's no relation? Setting the saturation to
zero results in (r,g,b) = (V,V,V) with V = max(r,g,b) and setting it to
one the (r,g,b) may or may not change.