Image Processing Tab
Default Processing Profile
Specify which profile RawTherapee is to use when opening a raw photo and when opening a non-raw photo. When you have made your own default profile, you can tell RawTherapee to always use that one. To do that, to have it show up in the list, you must save it to RawTherapee's "config" folder. You can find out where it is on the file paths page.
The default processing profile for non-raw files like JPEG or TIFF is best set to "Neutral". The "Neutral" profile just loads the photo as it is, without applying anything like Auto Levels or Sharpening.
Custom Processing Profile Builder
Executable (or script) file called when a new initial processing profile should be generated for an image. The path of the communication file (*.ini style, a.k.a. "Keyfile") is added as a command line parameter. It contains various parameters required for the executable or script to allow a rules-based processing profile generation.
This feature is very powerful; for example it allows you to set lens correction parameters or noise reduction based on image properties. It is called just once on the first edit of the picture, or called manually from the context menu when right-clicking on a thumbnail in the File Browser or Filmstrip
Note: You are responsible for using double quotes where necessary if you're using paths containing spaces.
Processing Profile Handling
"Save processing parameters next to the input file": When checked, RawTherapee writes a PP3 file with all the edits you made to your photo next to the input (raw) file. This represents your work (e.g. sharpening settings used) and can be reloaded later.
"Save processing parameters to the cache": Instead of creating a PP3 file next to the raw, this option - when checked - writes the PP3 to the cache. When you check the last option only, chances are that you lose your work (the edits) when installing RawTherapee on a new PC for instance.
It's usually a good idea to only save the processing parameters next to the input file, since you can e.g. back them up along with the your raws.
Dark-Frame
Specify the directory on your hard disk for searching for the dark frame shots for long exposure noise subtraction. File with coordinates listing of the bad pixels must be placed in the same directory for auto correction.
Flat-Field
Specify the directory on your hard disk for searching for the flat field reference images.
Film Simulation
Specify the directory which contains the HaldCLUT film simulation presets. See the Film Simulation article for more information.
Metadata
The option "Copy IPTC/XMP unchanged to output file" changes RawTherapee's metadata behavior. Usually it will remove all IPTC/XMP data from the input image and write only its own tags in IPTC section. This may become a problem when you tag your input files using other programs - raw files usually contain XMP data. This would be lost. By checking this option RT will not touch IPTC and XMP data at all, just pass them through. On the downside all your tagging within RT will not be saved though.