If you want to get similar contrast in darktable as in C1 follow these steps:
- First, convert that ARW file in C1 and output as a tiff.
- Then open the same ARW file in darktable and apply the C1 input profile + the unbreak profile module. Reset the base curve to linear. Then use the color picker: take live samples from the greyscale ramp which are representative of the whole spectrum of tones (sample an area rather than a point, set it to Lab space, mean value).
- Then open in darktable the C1-processed tiff and sample the same patches. Note down the values of the L channel for each sample.
- Go back to the raw file and use the base curve module to modify the L values so that they agree with the L values in the tiff file.
- Save that curve as a preset to be used only with the C1 profile.
- Test this curve on real-life photos. If the curve is very strong there might be some oversaturation issues, so you could consider using the Tone Curve module instead of base curve and modify the L channel only (with some slight steepening of the *a and *b channels to get some saturation so that it all looks good to you).