RawTherapee & Nikon DSLR Cameras
2017.08.20

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
Key steps are adjust the DCP profile and it's associated options, and setting the RawTherapee processing profile.  Then adjusting exposure setting.  The remaining options  (eg. white balance, noise reduction, ...) can likely be performed in any order.  Probably should reserve noise reduction alterations as one of the final steps, unlike it's indicated listed order below.

1) Color > Color Management > Input Profile > Color Management > DCP Profile
Ensure your camera model has a camera model specific DCP included within RawTherapee's code base, and this camera model specific RawTherapee DCP profile will be automatically enabled upon image loading.  Seeing that "Auto DCP" is the default or is always selected, this does not help users much from distinguishing whether or not RawTherapee is using a camera specific DCP profile.  (Posting to the RawTherapee user forums will likely inform whether or not your camera model already has an included DCP profile, or is still using a generic DCP profile.)

2) Color > Color Management > Input Profile > Color Management > DCP Options
The automatically detected (or your specified or embedded profile) should likely already have the following key options enabled.  Base Table should already be selected, and in my case, Baseline Exposure is checked and grayed-out.  The following key options should also be checked for Nikon (D5600) images, providing an eye-pleasing image versus color toning not matching the original camera processed image.  By default within RawTherapee 5.2, Tone Curve and Look Table are deactivated by default, regardless of what the hover-over info states!  Active "Tone Curve" and "Look Table" regardless of the hover-over info stating these further options are only activated if a DCP profile contains these features.  NOTE: This is the key option for making Nikon D5600 raw NEF images eye-pleasing or comparable to the in camera processed JPEG images!  I struggled for months trying to figure-out why in camera photos were not comparable to RawTherapee images.  Now you should be able to move forward in you image processing more easily, providing images slightly or far better than the in camera processed images!

3) Processing Profiles > Neutral
Use the NEUTRAL RawTherapee profile.  If you use the Default RawTherapee profile, I have little idea what you'll get at this point, aside from having an image comparable to being post-processed with Gimp's Color Auto Levels, having clipped whites and blacks with an adjusted gamma, providing a more contrasting vivid image; versus a (neutral) realistic duplicate of what you're naked-eye saw when taking the photo.  (The bundled Default profile for RawTherapee does provide an image similar to the end results of my instructions here, but I have some difficulty with color matching, etc?  I haven't re-verified if my results are still similar after activating DCP "Tone Curve" and "Look Table" options mentioned above.)


4) Might be a good idea to save the profile as a (eg. NIKON-NEUTRAL-D5600) custom profile now, are just after the next step, setting a minimal noise level.
 
5) 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!  Another note, be careful not to over-do luminance detail, as this option can create too much distracting color contrast.  The only detectable method is to compare the image to the original in camera process (JPEG) image, and make sure colors are not too over exaggerated or contrasting or overly vivid.  One might initially think saturation levels, but with these settings, we should not be seeing any over-saturation.  When reducing luminance detail, will need to likely reduce luminance levels as well.  NOTE: At higher ISO levels per camera settings, High ISO NR might be applied to only higher ISO's, or likely exposures using > 1600 ISO's.  I have no idea what is being performed when Nikon's High ISO NR is being applied, but do notice I have a particularly difficult time removing red/green/blue noise from dark 25600 ISO  exposures.  I have High ISO NR activated as I usually try to only work with < 1600 ISO, not expecting to work with the grainier >1600 ISO exposures.
    a) High ISO NR: Or, High ISO Noise Remove is something performed during in camera processing on Nikon cameras, for photos using >= 1600 ISO.  At 25600 ISO, High ISO NR usually becomes extremely desirable.  Unfortunately, this processing does not carry over for raw exposures with third party raw editors.  I've have found noise can be further suppressed by first using a 100% Luminance value while setting Luminance Detail to 0%.  Choose the Manual Chrominance option and increase the Chrominance Master channel from 15 to 40%, or more.  (Possibly, Activate Median Filter, increase Median Filter from 3x3 to 9x9, at the expense of processing time, although I've seen no difference here at 3x's zoom)  In brief, opting not to increase Luminance Detail provides an overall softer image, while increasing the Master Chrominance channel seems to resolve almost all noise.  Unfortunately, you'll likely need to first export/save the image in order to see these specific changes rather than trying to use the Detail Window!  Probably save a sidecar profile and name it "NEUTRAL-NIKON-D5600-HIGHISONR.pp3", and use instead of the usual "NEUTRAL-NIKON-D5600.pp3" sidecar.  I'm guessing there's like a bit flipped within the proprietary tags, and the Nikon Capture NX-D editor institutes a similar escalated noise removal such as this one described here.  (Almost looks as if some sort of Active-D Highlighting might also be implemented within this High ISO NR process when comparing images here.)

6) 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.

7) 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.

8) 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.

9) 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.

10) 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.

11) 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.

12) 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.

13) Experiment using Exposure > CIE Color Appearance Model 2002.  Activate sub-option "Tone mapping using CIECAM02?  For RawTherapee, the default Color Appearance Model used is CIELAB (1976) (eg. L*a*b*), while CIECAM02 (2002) is a more recent color appearance model.  Per Color Appearance Model Wikipedia for CIECAM02, "It performs better and is simpler at the same time.  Apart from the rudimentary CIELAB model, CIECAM02 comes closest to an internationally agreed upon 'standard' for a (comprehensive) color appearance model."  But on this note as of the year 2017 and only related so far as the term "international" is concerned, I still prefer to using ASCII character sets on all my computers instead of UTF-8.  I reside within the US and have no need for the extra UTF-8 characters, causing confusion and further bugs with programs.

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 results, if not far better.