weegee wrote in post #14423673
hmmmm. Maybe I asked the wrong question then.
Is there a way to tell you are over exposed to blown out levels in LR3? Can you read one of the RGB percentage values or anything else to give you an indication?
Not exactly, only approximately. As said above, LR works in a wide gamut space. When you export you will most likely export to a medium (Adobe RGB) or narrow (sRGB) space. Think of it like a ball-park. The same hit will drop in for a single in ProPhoto Stadium, be off the wall for a double in Adobe Stadium and out of the park in sRGB. (Except in our game home runs are a bad thing and doubles are undesirable.) A tone that is 240 in LR might become 248 or 253 in sRGB, depending on the color. The problem is there are no simple formulas for determining how much the shift will be because the distances from the (grey) center of each space to the red, green or blue primaries that define the limits of the gamuts are very different. In the illustration below the difference between ProPhoto RGB and sRGB in the green direction is huge and in the red direction sRGB and Adobe RGB are virtually identical and the difference from ProPhoto RGB is smaller. That means that Red 240 (94%) in LR might be Red 245 in sRGB, although Green 240 would be clipped in sRGB.
That is one off the reasons why softproofing in LR4 is so welcome. In LR3 the best advice is to leave some head-room above your white point, how much exactly is impossible to say. I always used to set the white point at around 96% and if it was important to check the histogram of the rendered image in a pixel editor and if necessary do a levels adjustment.
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