RawTherapee & Nikon DSLR Cameras
2017.08.08

Here are some tips for editing Nikon RAW NEF files using RawTherapee, more specifically for Nikon DSLR camera models which already have a camera model specific DCP color profile included within RawTherapee.

If your Nikon DSLR camera is not already supported by a previously submitted camera model specific DCP color profile for the RawTherapee project, you can easily create a camera model specific DCP color profile by purchasing an X-Rite ColorChecker (Passport), taking a few photos of the ColorChecker and submitting them to the RawTherapee project.  Knowing whether your DSLR camera model already has a camera model specific DCP color profile submitted to the RawTherapee project is not easily readily known, usually requiring the user to query the RawTherapee project forums.  The RawTherapee program automatically chooses Automatic for DCP support, and the program does not display whether the RawTherapee program is using a camera model specific DCP profile or the basic generic DCP profile.

For myself, the Nikon D5600 did not have a camera model specific DCP color profile yet submitted to the RawTherapee project, and required going through a brief process of submitting a bug report along with my X-Rite ColorChecker Passport photos.  Once performed, your colors will look much better and comparative to Nikon's processed photos.

Here are some tips or bugs I noticed when using RawTherapee 5.2, and the following will either be resolved or will help you with processing your Nikon NEF raw image files.

NOTE: Switch-off Active D-Highlighting within the camera, as Nikon ADL adjustments negatively effect the raw image file when importing into third party RAW editors.  (Active D-Highlighting is apparently proprietary.)  All other settings have little to no effect on the raw image file when importing into third party RAW editors.

NOTE: I prefer, Neutral picture control.  I also tested and use High ISO Noise Removal set to High, which is applied to ISO settings greater than 800/1600.  Most of these settings are geared towards the JPEG processed image.  The Nikon D5600 seems to have noticeable noise at ISO settings above 1600.  Once set, the maximum ISO I use is 1600, reserving higher ISO values for when the camera automatically uses those higher ISO values.  During my brief testing, High ISO NR had no noticeable effect on images less than 1600, with only positive effects on ISO values 1600 and higher when set to High.

NOTE: For still photos or photos I value, I prefer having the camera save to RAW files only, as the Nikon RAW NEF file already includes an embedded 2MB JPEG and having an extremely similar quality with the Nikon D5600 6MB JPEG files.  For photos requiring continuous release mode resulting in many photos, such as moving objects, I tend to prefer JPEG Fine.  Use Linux/GNU Geeqie for readily viewing NEF files using the embedded 2MB JPEG image.


RawTherapee Processing Steps for Nikon RAW NEF Files

1) Color > Color Management > Input Profile > Auto-Matched Camera Profile
Ensure your camera model has a camera model specific DCP included with RawTherapee's code base, and the camera model specific DCP profile will be automatically enabled upon image loading and only indicated by having "Auto DCP" selected.  (Doesn't help users much, as "Auto DCP" profile is almost always selected.)

2) Processing Profiles > Neutral
Use the NEUTRAL RawTherapee profile.  (The bundled Default RawTherapee does provide an image similar to the end results of my instructions here, but I have some difficulty with color matching, etc?)

3) Detail > "Noise Reduction" > Luminance & Luminance Detail
You'll almost always likely have to enable Detail > "Noise Reduction" > Luminance & Luminance Detail options, unless the photo was taken within extremely bright conditions from my experience.  Regardless, enable noise reduction and I usually set 100% Luminance and 40-50% for Luminance Detail.  BIG NOTE: Sometimes noise  reduction does not immediately show within either the image OR when using the Image Detail Window.  (Middle right bottom icon, indicated with a square with a plus sign in the upper right corner.)  Almost all the time after I save the image (eg. CTRL + S) and viewing within The Gimp, I find noise reduction did perform extremely well.  This seems like a bug, as users should see noise reduction always occur within the 100% image detail window, but in reality sometimes just does not show noise reduction!

4) Exposure > Exposure Compensation
At this point, adjust the exposure of the image.  I usually find I always need to reduce the exposure by a .5 to 1.0 value.  (Exposure compensation setting is apparently not the job of the color DCP profile.)  What I usually do is use Geeqie to view my Nikon NEF raw images, in which Geeqie displays the 2MB embedded NEF JPEG image, far quicker thank Windows does I might add!  Using the embedded NEF JPEG image as a reference image, I then set the exposure compensation within RawTherapee to something similar to the embedded NEF JPEG image, and further adjust the exposure compensation to my liking.

5) Color > White Balance
If you took a white balance photo, you should probably apply a specific white balance value to the image now using the dropper within the Color > White Balance menu.  (NOTE: The white balance image should be white, or a very slight not noticeable gray, while the middle 18% gray is noticeably grayer and used for setting manual exposure instead of using the auto exposure shutter button while taking the photo.  However I commonly hear people using the 18% gray patch for setting white balance too.)  The set White Balance value can be copied to the other photos within the film strip displayed images.

5) Exposure > Black; Exposure > Light
You may also need to adjust the Exposure Black and Light levels, similar to image darkness and brightness levels.  I also use the embedded JPEG as a point of reference, and customize to my liking.

6) Exposure > Contrast; Exposure > Saturation
Finally, adjust the Exposure > Contrast and Saturation values to your liking.  May not be needed after adjusting the Exposure > Black and Exposure > Light values.

7) Transform > Lens Correction Profile (Using RawTherapee Plexiglas trick exact removal of vignetting.)
Transform > Vignetting Correction (User manual adjust vignetting... guess work!)
Depending whether you used a zoom or telephoto lens, you may need to adjust for vignetting.  RawTherapee has an article on how to create your own lens profile for taking a series of lens specific profile photo images using clouded Plexiglas, for automatically removing vignetting according to the profiled used lens.  Or, just use the guesswork method.

8) Transform > ? (Correct barrel and pincushion distortion.)
If you're using a Wide lens, you'll likely need to remove the lens distortion, commonly called barrel or pincushion warping.  Not sure how this is performed yet, but later Nikon models have an in camera menu item for selecting automatically applying lens correction to the raw image.  Not sure if this is carried over to RawTherapee imported images, but I would think this would occur.

9) CTRL + S
Export the image to JPEG, TIFF or your preferred image file format for importing for using within ImageMagick or The Gimp.  Double check to ensure noise reduction took effect and all your other image corrections look good.

For most images, you'll likely be finished at about step number six above.  Number seven is likely for 300mm or full zoom/telephoto photo images, while number eight is usually for wide-lens.  Once you learn the above hurdles, you'll find RawTherapee does a pretty darn good job alongside Nikon's proprietary specifications.