RawTherapee dcp and lcp files...

I need to remember something detailed.

 

 

In using RawTherapee to process RAW files I've found it has sophisticated color and lens management systems.

Interestingly, RawTherapee accepts industry standard dcp and lcp files.  dcp files are for color management and lcp are for lens corrections.

Rawtherapee comes with some dcp and lcp files on installation which appear to be updated from time to time.  I'm not sure who generates these files, but they seem to have done a good job for the lenses and camera models covered by the software distribution.

However, I found some of my cameras (Sony NEX, A6000, A5000, A7) and lenses (Sigma 24mm and a few others) are not supported by RawTherapee automation for the version I'm running (the latest), so I set off in search of good dcp and lcp files to fill in the gaps.

It turns out a certain RentWare implements these two file formats for their own color and lens management systems.  I wondered if I might be able to borrow them?  I run Linux, but have a computer that can boot into Windoze.  Here's what I do.

Boot into Windoze and...

• In a browser search for "Adobe Camera Raw download" and locate the Adobe site (there are other sites that may offer downloads, but they are highly suspicious and I avoid them like the plague)
• Download the latest "Camera Raw" plugin (I do not want LR or PS, just the RAW converter part)
• Execute the "...exe" file to unpack the plugin
• Descend the "c:\ProgramData\Adobe..." folder structure to locate "CameraProfiles" and "LensProfiles"
• Copy the contents of these two folder structures into a Linux readable location/media

Boot into Linux and... 

• Copy the "CameraProfiles" and "LensProfiles" directories and their contents somewhere under $HOME where I can easily find them
• Open RawTherapee
• Open an image and...
• Under Color Management 
• Select "custom"
• Open the directory box
• Locate the "camera profiles" directory
• Descend the directory to...
• Locate the camera model
  
• Under "Profile Lens Correction" 
• Select "LCP file"
• Open the directory box
• Locate the "lens profiles" directory
• Descend the directory to...
• Locate the right lens
•  The base image is now configured using good dcp and lcp configurations.
  

Under "Lens corrections" there are selections for "Geometric distortion", "Vignetting", and "Chromatic aberration."  I turn off "Vignetting" because I've found that correction to be too strong for my taste.  But I do turn on "Geometric distortion" and "Chromatic aberration."

Under "Color management" there are selections for "Tone Curve", "Base Table", "Look Table", and "Baseline Exposure."  These are defined here.

On a practical level here's what I do.

• Open an image in Rawtherapee
• Let Rawtherapee select the demosaic algorithm (long topic for another time)
• Set the lens profile
• Select the color management dcp to be used (more on this in a moment)
  
• Select "Tone Curve"
• Select "Base Table" if selectable (this is not always implemented in some of the dcp files I've seen)
• Select "Look Table" to get the dcp files color grading (which can be glorious, BTW)
• Unselect "Baseline Exposure" since there is no jpg reference (read the definitions linked to above)

If I want to make further changes to "Curves", I go to the...

• Eexposure panel
• Find the curve function
• Select "Luminance" 
• _Then_ make adjustments to the curve

This keeps the colors from shifting.  Remembering, of course, that standard curves modify RGB curves at the same time the luminance curve is changed.  This modifies the color of the image, which I find I do not want to happen since  I like the "Look Table" results and do not want them to change.

From the list of practical things that I do I said I would comment further on selecting a <specific camera model> dcp.  The RentWare distribution is a little complex in how they've implemented their dcp directory structure.  Basically, it comes down to this.  Under "CameraProfiles" we have two ways of further descending the directory structure.

• "...CameraProfiles/AdobeStandard/<specific camera model>.dcp"
  
• "...CameraProfiles/Camera/<specific camera model>/<several dcp to choose from>

I'll start with the ".../Camera/<specific camera model>..." profiles.   From what I can tell these are the RentWares attempt to match specific image style selections offered by the manufacturer.  For instance, with the Sony A7 there are vivid, neutral, standard, landscape, and other dcp selections found in this directory.  If I want an image to look similar to the in-camera style selection, this is a good place to start.

Looking in AdobeStandard/... directory I see the RentWare has offered something a little different.  This is appears to be their own interpretation of what a "good image" would start with.  I find in the case of the Sony A7 that the ".../AdobeStandard/Sony ILCE-7 AdobeStandard.dcp"offers a more muted yellow, for instance, color starting point than the Camera/<specific camera model>/... "standard" dcp.  It pays to experiment and experience these various dcp options.

You notice that I've said nothing about using the RawTherapee "Processing Profiles."  This is because I've found the automated selections to be too strong for my quickly evolving image processing tastes.

OK.  There it is.  Lots and lots of detail.  But if I save a base processing configuration, the processing workflow can collapse to a single button push.  It's pretty sophisticated stuff, but I'm learning it's well worth the while to understand what's going on.