Sorry for the off-topicness coming in this message, it is about color fidelity though, and I thought I'd share some of my recent findings of the internals of C1 which some of you might be interested in; I've been working with my profiling project (which does both DNG and ICC profiles) and some of my users want to use it in C1 so I had to dig into it whether I like it or not
I've been quite critical against C1 for using a simple RGB curve as their tone curve, and letting you change curves without changing profiles. As an S-curve RGB curve adds loads of saturation and shifts hues it's not exactly what you would think would be used in a high end raw converter. C1, like most established raw converters, was created in the 1990s though when computers were a lot less powerful than today so using simple algorithms like RGB curves was natural and this legacy is still in.
However, C1 designers have known what they're doing, the RGB curves found in the film curves are never a pronounced S, and will thus only cause small hue shifts. However such curves does not provide that much contrast either, in particular the shadow range becomes light and the overall look a bit dull. This has been solved by adding an additional fixed contrast curve in the ICC profile lookup table (LUT). By having it in the lookup table they can have used any type of curve algorithm processed offline, my guess (without analyzing in detail) is that they've used some sort of luminance curve to avoid hue shifts. This split approach to contrast makes the profile work better across several film curves.
However, it does of course also mean that if you apply "Linear Response" you still have the residual S-curve that the ICC applies, so it's not by any means an accurate colorimetric mode. The change of curve is still not totally immune to hue shifts either, and one can assume that the ICC profiles are optimized to look the best with the default curve.
I've mostly worked with P45+ as the test camera though, so I can't say if all C1 profiles work this way, but I'd guess so.