I see nobody answered this… so I'll answer with the caveat that I'm the author and thus biased. But I did use RT before making Filmulator, and I still use it in conjunction occasionally.
RawTherapee does no photo management. Filmulator does.
RawTherapee has many ways to achieve a given result, with tons of flexibility, but gives little guidance as to what's best for what. Filmulator only has one tool for each job, and is much less flexible overall—but it's easier to learn.
RawTherapee can edit jpegs and tiffs. Filmulator only edits raws.
The UI philosophy for Filmulator is to never add things before making them fully usable and easy to learn. I like to point to the cropping tool as a significant pain point in RawTherapee that I was able to implement more elegantly in Filmulator.
> RawTherapee… gives little guidance as to what's best for what
Not sure about that. RawPedia is chock full of information relevant to pre-production (calibration, etc.), photography and post-production techniques, along with advice on development tool usage. I’ve learned a lot from it, which will stay with me even if I move away from software itself. It’s one of those tools with educational documentation that doesn’t just explain what the tool does but actually teaches a lot about the problem domain (similar to docs for DCamProf, which has the same maintainer).
> RawTherapee can edit jpegs and tiffs. Filmulator only edits raws.
Most software can consume DNG but almost nothing, except for camera firmware, can produce it. RT’s ability to edit 16-bit TIFFs output means it can participate in diverse workflows with other raw processors.
(For example, I use Siril to combine multiple exposures, and then can still apply a RawTherapee profile with all the numerous curves, Lab, film emulation, CIECAM and other power tools that get my pixel data into output-referred image state. Of course, some controls behave differently with a 16-bit TIFF than when a DNG image, but it’s not that difficult to adjust to that.)
Filmulator, on the other hand, can’t be used other than at the very beginning of the workflow, which takes away from its flexibility.
That said, RT sort of stands alone so far, and more open-source software that can compete with it can only be appreciated as far as I, a happy user, am concerned.
