Yes! That occurred to me as well .
IMHO your problem is the DNG file - everybody assumes that converting to DNG is a lossless conversion but it isn’t. They do normalize some of the data contained in the original RAW file (most notable the black point data has often been mangled and even at times falsely interpreted and some of the masked rows and columns of the sensor were previously discarded) and transform them to a common denominator by embedding a camera profile which must be adhered to by the development software. The original RAW file OTOH will be interpreted completely by the RAW converter which will apply it’s own camera profile.
If you were to extract the camera profile from the Adobe LR or RAW converter library and instruct RT to take that one to convert the image I’m willing to bet that the results will be practically identical.
I made three test using the color picker in photoshop:
test1- rawtherapee: orf and dng are always different ( even without colormatrix or the same colormatrix)
test2-cameraraw: orf and dng match perfectly
test3-darktable for windows: orf and dng match perfectly
My camera can save both DNG and a vendor specific raw format PEF I’m not sure it’s useful but if you want to research if it’s a general bug you can find files here: https://filebin.net/005fe0bioakmcuhp
DNG, PEF processed twice once using Neutral and once with the standard Pentax dcp applied. It’s really sunny here and i’m doing this whilst caring for a sick child (nothing serious) so I’ve not analysed the results. The light changes a bit unfortunately. I can do static shots with off-camera flash if it’s useful.
Edit: after looking closer at the images I see the light (and background due to wind) changes to much for the images to be useful.
Edit2: Looks like Neutral profile does some things different with PEF and DNG after all.
It’s conceivable that the PEF is a bit brighter pushing it over the edge but I doubt it as the DNG is also blown out.
@nosle (and all) thanks for the help. We are already digging into this, please check https://github.com/Beep6581/RawTherapee/issues/4129 if you are interested
Sorry I don’t have a github account but following the discussion I’d like to add that I would find it useful if RT could make full use of all DNG colour settings like matrices WB etc. In Darktable the DNG embedded matrix becomes an option if available. It’s sometimes useful to be able to replicate the camera settings as closely as possible. In RT you have to get hold of the settings from the Adobe software when it’s already embedded in the DNG.