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1. Re: Missing One of Three Blend Mode Constraints
George Austin Feb 4, 2010 5:31 PM (in response to George Austin)That there have been no responses may be due to my poor presentation of the question. I'll try again.PS books and other sources I have checked give the parameter values for hue, saturation, and luminosity resulting from Hue, Saturation, Luminosity, and Color Blend modes as either the base or blend value, depending on the mode. While this is correct for hue and luminosity, saturation values resulting from any of these four blends DO NOT comply. The definitions used by the authors are supported by Photoshop Help, and probably have been engendered by PS Help. In practice, however, they do not pan out for the saturation parameter. Let me demo the saturation deviation by just one example, taken at random from more systematic sampling (saturation values are in red):Base color: RGB 177/25/37, HSB 355/86/69, luminosity 72Blend color: RGB 115/74/54, HSB 20/53/45, luminosity 84Resulting colors:Hue Blend Mode: RGB 146/49/1, HSB 20/99/57, luminosity 72Sat Blend Mode: RGB 114/53/58, HSB 355/54/45, luminosity 72Lum Blend Mode: RGB 189/37/49, HSB 355/80/74, luminosity 84Col Blend Mode: RGB 103/62/42, HSB 20/59/40, luminosity 72NONE of the resulting saturation values match either the base or the blend saturation values, whereas ALL of the hue and luminosity values do. Luminosity values are given by 0.3R + 0.59G + 0.11B, the definition used in PS, but their tedious calculation can be skipped via a neutral layer in any of the four modes placed above the blend layer and turned on only to read luminosity (the resulting gray value).This leaves a problem. While luminosity and hue constraints on the resulting color are exactly defined, we still need a third constraint in order to fix color---which requires three independent parameters. Brightness of the base or of the blend is NOT preserved. If it's neither brightness nor saturation, what is that third constraint?EDIT: Hard returns have been ignored. Even multiple hard returns do not separate paragraphs as before. So please excuse the crammed format.

