conserving linearity


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sharkacos
conserving linearity

I am doing a scientific experiment where I shoot HDR cross-polarized and parallel-polarized images and subract them to derive specular reflections. It's critical therefore to avoid the "enhansements" that Adobe Camera Raw automatically adds, such as applying  gamma correction during the conversion to TIFF (or other formats), and adding some contrast enhancement by default, and some blackbox color tweaks for aesthetic reasons.

I am therefore using cdraw to avoid this, using Lightzone as a front end GUI. In dcraw I would use the options: -v -4 -T [ file ] which would create a 16-bit TIFF to keep a 16 bit linear work flow. No gamma applied, no automatic brightness correction. However, the convert options for Lightzone add in a couple options that are not part of dcraw.

color profile (set to sRGB IEC61966-2.1) rendering intent (set to Absolute Colormetric)

I don't see a way to disable either of these, so I wanted to confirm that this is the correct settings to use to avoid any sort of color or brightness changes being made to the RAW images upon conversion. The rendering intent looks like it is a form of brightness correction, which I would like to avoid.

 

tex
I'm sorry no one has commented yet

I was waiting for someone who knew more about the particulars of this issue to jump in.  I don't know the answer for sure.  What I will say is this:  LZ was originally designed with amateur photo editing in mind, yet had some professional capabilities built in.  This particular issue I can see would be very important for some applications.....but they are pretty narrowly specific and not ones the creator and original designers necessarily had in mind when LZ was created, and I don't know that any subsequent additions and upgrades addressed this point.  And of course I note with interest that more "professional" applications don't seem to do what you need....