Disclaimer, before I start: I’ve messed with the dt filmic module just enough to know I need to go and watch @aurelienpierre’s videos… so, I do not have specific knowledge about how they work.
But, I do know the fundamental characteristics of a filmic curve, and to me that’s important to developing heuristics regarding its use. Essentially, it’s log-like, with a toe on the left end. You play with the toe to “crisp-up” the blacks, and you play with the shoulder and central linear line to mess with the overall tone distribution. In rawproc, my tone tool has a curve plot to show one what the selected tone operator and its parameters will do to the image, and I’ve found that to be of critical importance in applying it to particular images.
For instance, my test raw for rawproc is a scene with a specular highlight (locomotive headlamp), a mid-morning cumulus-cloudy sky mixed with locomotive steam and smoke, and a triple-headed train where the locomotives sport various shades of gray-to-black. When I scale the image to fit black-white where the headlight is blown (don’t yell at me @heckflosse, I’ll get around to figuring out librtprocess highlight recovery… ), it almost looks good as-is, linear. Indeed, when I put the basic filmic on it, the steam, smoke, and cloud definition gets lost in that rather lofty shoulder headed to white. Really, I’ve found that the best curve for this image is a custom curve with two control points: one on the exact center of the line, unmoved, and a lower one drug slightly below the neutral line to pull the shadows down a bit.
So, summed up, here’s what I think is important about any tone curve selection:
- know what linear looks like for the particular image, and,
- know the transform curve of whatever tone operator you apply to move from linear.
That’s it. log, log-gamma, reinhart, filmic, custom; same two fundamentals.