When I look at attachment #27132 I do not see any difference between the two windows. Also, all of the Matte entries are [0 0 0], and given the equation in the PDF reference: ,----< from PDFReference1.7.pdf, §7.5, p.554 > | c′ = m + α × (c − m) `---- Matte should not make a difference; it should simplify to c′ = α × c. (Just curious.)