I just can say that there is no clipped channel in the raw.
You can be told if there is clipping yes, due to over exposure. You can't be told if there is color clipping; there's no color, per se,
yet.
And may I add that if there are no clipped raw channels - and even a good bit of headroom - the Foveon conversion matrices have pretty big coefficients including the off-diagonal ones. And I'm talking camera-to-XYZ - an even bigger space than ProPhoto as of course you know.
Sensor Inputs refers to bottom, middle and top layer signals.
An early matrix for the SD9 - later ones vary.
For example, if I put equal layer exposures, with 1 EV or so headroom, into the Sigma SD14 cam-XYZ matrix, I would naively expect to get something near a white point out of the matrix. But no, it gives XYZ = 0.55, 0.39, 0.91 and that transforms to an x,y chromaticity of 0.3, 0.21- placing the white point nowhere near neutral, more a light purple I reckon.
Main point, since I digressed, is that lack of clipping in the raw is no guarantee that the RGB will not be clipped.
never learned fundamental exposure, something that's photography 101 without the lie of the Histogram as perhaps a crutch. Would having a raw Histogram be useful on camera? Sure. Must we have one? No. But don't look at a Histogram built from and based on a camera JPEG and expect it has bearing on the raw data or is necessarily to use one to optimally expose.
