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The111
28th of September 2007 (Fri), 14:53
I have been reading a lot about "luminosity masks" and their use in blended exposures. I have a few issues with this that I'd like to hear others' opinions on.

1) The "lumnosity mask" is a misnomer. There is no reference to this term anywhere in Photoshop documentation. There are tutorials all over the web saying to hit "ctrl alt ~" to load the selection for a luminosity mask, but after reading PS help all I can find about this keyboard shortcut is that it loads the RGB alpha channel. The only reference anywhere to luminosity is in the histogram... and since in the histogram RGB and luminosity are not equal, why should the RGB channel be called the luminosity channel, or the source of a "luminosity mask?"

2) All nit-picking about nomenclature aside, I don't think this technique works very well for blended exposures. I've done a few blended exposures in the past that were very time consuming because I basically used a fade brush to manually create my mask. Today I tried using a "luminosity mask" on several blended exposures (one slighty overexposed and one slightly underexposed), and while the end result was certainly better than either picture, I got much better results (and quicker!) with judicial use of the "shadows/highlights" tool applied to the underexposed image. Anybody else have any similar experience, or am I doing something wrong?

Thanks!

The111
28th of September 2007 (Fri), 15:15
Hmm, I just realized that the radius on my gaussian blur of the mask was way too low. Raising it up to about 50pixels (8MP image) makes a gigantic improvement. This method actually works pretty well.

I still have an issue with the terminology. ;-P

René Damkot
29th of September 2007 (Sat), 08:44
I'ld guess a Gaussian blur of 50 px would give a bit of an outline around edges. Then again, might be soft enough to work.
I mostly use a feather of about 2 on the selection, and a gaussian blur on the mask later on.

Here (http://photography-on-the.net/forum/showthread.php?t=362356) is a(n extended) tutorial of how I do it...