Re: GM -normalize without clipping highlights

Interesting discussion, though somewhat over my head.  I'm just an end user, I 
like simple commands doing a job.

If the only way to overcome highlight clipping that GM -normalize produces is to 
write a script, then I'll stick with what I've done.  It's relatively fast and 
has the benefit of bringing in IM's colour balance, which helps when GM gets it 
wrong.  It does happen, on a picture of a girl in a park, with green foliage 
behind her, GM -normalize tinted the whole picture green.  IM's 
-contrast-stretch 0, on the other hand, produced correct colour balance (on this 
image), so when I paste that over GM's output, masked to apply over highlights 
mostly, it helps to correct things.  So maybe I shouldn't complain and be happy 
I'm using two algorithms that correct one another.  Still though, GM -normalize 
is in most cases superior, and I don't enjoy the wrong colour balance intruduced 
by the IM code that I use to correct the blown highlights (that code being IM 
-contrast-stretch 0 mentioned above).

I must say I haven't noticed GM -normalize clipping shadows, perhaps I need to 
test more.

">From what I have seen, 'dcraw' has the best access to the camera raw 
data information (including proprietary camera metadata) so it will 
always be more competent at applying automatic corrections than 
follow-on software like GraphicsMagick."

Not in my tests!  Dcraw may have best access to raw data, but once that data is 
decoded, the data is like any other 16bit file.  And in all the extensive 
testing of dcraw output that I've done, GM's -normalize is by far superior, even 
IM's options are better.  Dcraw simply does not stretch values as it should, 
even without the -W setting, and no matter which -H is used or whether it's -a 
or -w.  I definitely don't trust dcraw to process my files, I employ all the 
settings to get as close to "raw" data as possible.  The only processing I allow 
dcraw to perform is set the gamma, with -g 2.4 12.  This brings up the light in 
the shadows and lowers the contrast somewhat toward the highlights.  It helps in 
the further processing that is done with GM and IM, and it ultimately helps in 
post-processing.  I only need to bring up the highlights a small amount if at 
all (the "knee" I mentioned), but mostly I lower the curve to darken the image. 
 Since I do this in GIMP at 8bit, I think it's the best procedure.

Thanks for listening, I hope I've given you some food for thought as you develop 
things down the line.


      


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