Built and installed DT5 from source and found I needed to re-download the LUA script manager from git to have it show in the left panel but that was a minor issue.
As to the built-in camera-specific styles, I found their location (/usr/share/darktable/styles) and tested the Pentax K-3, KP and K-1_MKII styles as I happen to own those three cameras.
Weird thing happens on the K-1 MKII style (whether manually applied or auto applied through LUA) the exposure is set to +1.5 which is far too much IMHO. Same file but with the regular K-1 style (as well as the KP) shows an exposure setting of +0.5 which is more in line with what I’d expect as well as closer to the OOC jpeg.
I dove into those camera-specific styles but they show a value called [op_params] for the exposure and other than establishing the value shown in the K-1 vs the K-1_MKII is slightly different I have not found any of the definitions of how this hex value is built in the documentation or in the source code.
Anyone? How is the hex value in [ops_params] built and how would I change it to suit a personal preference (exposure in my current case)?
These camera styles can be a nice starting point, but for me with my Canon R7 I opened a representative JPG image, took a snapshot and then opened the raw file. I then started tweaking settings to get the exposure to match the JPG which was about +1 EV in my camera’s case. I then tweaked contrast, shadow highlights correction, saturation and even a minor color tweak in color zones. This gives me a nice starting point and I saved it as a new camera style which also includes initial sharpening and denoising. I can’t help with the hex values but maybe just tweaking the camera style to suit your preferences and expectations is an easy way.
Here’s an earlier reply I wrote on decoding param values from sidecar xml files, and I expect it’s similar (if not identical) for styles. The struct for the exposure module can be found here in code.
Rather than updating the value in this way, it may be more straightforward to create a new style (based on the original) and make the change to the exposure module in the darktable UI.
Alternatively, you could create a style with your desired exposure settings and simply copy the parameter value from that file rather than encoding a new set “from scratch”.