This topic discusses extracting ICC input profiles from Nikon CaptureNX software. I played with this a while ago.
Does anyone do this? Does it really make a big difference?
I tried it ages ago but never used it - I usually adjust my colours so much that slight profile differences are of zero consequence.
I don’t know if they could be more useful for accurate reproductive work, but you’d really want a custom profile there anyway.
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Yeah, for reproduction work I’d want to make a profile from the scene’s illumination. The Adobe DCP workflow attempts to approximate that using two profiles and an interpolation between the two based on a calculated color temperature, but I cannot imagine that gonkulator even coming close to a target-shot profile from the scene’s illuminator.
Not particularly related to Nikon .icm profiles, just wanted to say that… 
I also tried them once, but the difference between them and a well-constructed target-shot profile like what the softwares contain is negligible.
Is a well constructed target-shot profile one created with the colour calibration module and a colour target, or do you mean something else?
I was actually thinking of an ICC input profile, generated using the same target shot but with dcamprof or similar, but the colour calibration profile works exactly the same way.
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There are a number of ways to do it, but the common denominator is a shot of a color target under a particular light source. Most are done under mid-day sunlight, roughly corresponding to the D65 color temperature reference. The predominant target is the X-Rite (now, Calibrite) 24-patch ColorChecker, but there are others with various patch populations. What’s needed for the target is a reference file with its measured XYZ values for the software to use in comparing to the patches in the target shot.
For software, I also use dcamprof to make my .icc files. I gues dt has equivalent software built-in. X-Rite (Calibrite?) also has software, but it costs. The fellow who wrote the open-source command-line dcamprof program also has a GUI version with more capabilities, LumaRiver, also costs.
I am not sure if a ICC profile from Nikon’s software would translate accurately to another program including DT. However, I created my own Canon R7 style in DT that would effectively achieve the same desired result. I created this by selecting a well exposed daylight picture with skin tones neutral tone areas and parts of the image which were strong colors of red, green, blue, yellow. It was actually a street scene from Japan with a couple of girls posing for a shot.
First I opened the camera’s JPG and took a snapshot. I then opened the RAW and used the snapshot as a comparison.
I set the exposure slider to match the JPG
I set color calibration to as shot in camera
I applied basic denoising and sharpening
I applied default local contrast
I increased contrast in the sigmoid module to 1.7
I applied shadow and highlights module at default values
I did some tweaks in color balance RGB module to adjust shadows and contrast
Finally I did some saturation tweaks of various color zones to lift the saturation of the reds in the image to better match the color look of the JPG.
This style was then saved and with one click I get a great starting point for my edits. I plan to do this for all of my cameras. BTW, a landscape style might need to lift the saturation of the blues and the greens where this Canon R7 style needed more warmth in the skin tones and hence the color zones adjustment.
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Darktable uses ArgyllCMS I beleive. I have a colour checker passport and have used it to profile. I just wondered how usefull the Nikon ICC profiles are in actual practice.