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PS: Since linear RGB pixels values are typically gamma-encoded representations of some absolutely recorded brightness, I suppose technically for a double-exposure you would have to un-encode the gamma (e.g. apply a Levels adjustment of 0.45 or so), merge the two source layers using Addition blending, then re-encode (e.g. 2.2 Levels adjustment). I did some experiments using two layers with black-to-white gradients rotated 90 degres from each other, and the result of those adjustments was indeed pretty close to the "Screen" blending mode. That's pretty interesting.
-- Stratadrake strata_ranger hotmail com -------------------- Numbers may not lie, but neither do they tell the whole truth. Date: Sun, 4 Nov 2012 16:18:39 +0100 From: tobias lunte hfg-gmuend de To: ellimae288 gmail com CC: gimp-user-list gnome org Subject: Re: [Gimp-user] double exposure Hello, afaik, the "Screen" blend mode is a more accurate reproduction of a double exposure. However, it will brighten up your image, so if the two photos weren't underexposed to begin with (which they are when you actually make a double-exposure on film), you'll have to adjust the values. Don't worry, the Screen mode doesn't result in clipping, so usually you don't loose all that much information. bw, Tobl Am 04.11.2012 16:10, schrieb Richard
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