Hi @Mister_Teatime, thanks for sharing this very interesting work.
If I understand correctly you are not simply proposing an alternative parametrization of the existing filmic curve, but a somewhat different curve (the bit where you talk about the Michaelis-Menten curve).
If this observation is correct: wouldn’t it be a better approach to keep the current curve exactly as it is and only revise the parametrization? The advantage would be that this could be done in a perfectly backwards-compatible way.
I have two gripes with filmic’s parametrization in its current form:
- The overshoots you mention when contrast or latitude is too high.
- The fact that actual midtone contrast is not preserved when white and black point are adjusted. See here for details.
Here is one possible way to deal with the above while keeping filmic’s exact spline and changing its parametrization only slightly:
- Filmic could reduce latitude as much as necessary in order to avoid overshooting. Rationale: an overshooting and therefore clipped curve is likely a more extreme departure from what the user had in mind than a curve with reduced size of the linear section.
- Instead of the currently used contrast parameter, filmic could keep the midtone contrast constant. I also think that midtone contrast would be a better parameter than current “contrast”. See the above post (Part III) for details. Rationale: everything in filmic revolves around the midtones, so controlling the contrast of the midtones directly seems like a good idea.
The above is not a complete proposal yet, but it shows the idea.