Hmm, this is a short question with many possible answers. I’ve been experimenting with PhotoFlow filmic curves:
There are links in the above thread to some nice papers. But the PF filmic stuff is not easy to control, and further discussion of the PF filmic curves should probably be done in the above thread (where I’m planning to make a post in the next hours or couple of days).
The base curves in darktable are well worth looking at - there are presets that emulate various camera styles from various camera manufacturers - these curves are all basically “film like” and can be modified until you see something you like, and then you can save a new preset.
What you are asking for is basically just Curves, but finding the right Curves algorithm and interface isn’t the easiest thing to do. I’ve been trying to figure out those HD curves myself, but I suspect you know a lot more about them than I do.
Any “film-like” or “print-like” curves shown in various digital imaging forums are suspect from the get-go unless they specify the actual RGB working space.
Most algorithms and LUTS that purport to be film-like fail to mention to the user that the actual tonality of a paper print made using traditional darkroom processing depends on the film, the film exposure and processing, the paper on which the film is printed, and the process and chemicals with which the paper is developed. So at the very least that nice highlights rolloff in a paper print is the result of not one, but two “wet darkroom” transfer curves, each of which depends on many variables. This is why I find the PF filmic tonemapping both intriguing and frustrating - all the ingredients seem to be in place, but I’m having trouble getting the sliders to correlate with what I think I know about the things the sliders seem to be emulating.
Other people hopefully will chime in with references to algorithms in various softwares for emulating the rolloff in the highlights achievable using traditional darkroom techniques.