Lightroom is the current king of the castle when it comes to processing and organizing RAW images. It’s the most widely used and has the largest presence. But it’s not necessarily the best option for every photographer. There’s the issue of being on the hook for an ongoing subscription. And there can be quality, workflow, and feature benefits to other Lightroom alternatives (eg. Capture One, Luminar, ON1, etc) that some photographers might prefer.
RawTherapee is RAW image editing software. It’s free and open-source, with versions for Windows, Mac, and Linux. At the time of writing, it has been a couple of years since there’s been a new RawTherapee update, but it has been actively developed since 2005. 
My objective here isn’t to provide a comprehensive guide to using RawTherapee (for that, I recommend starting with RawTherapee’s dedicated documentation site RawPedia). Instead, my aim is to provide a brief overview, coming at it from the perspective of whether RawTherapee makes sense if someone is looking for a free Lightroom alternative.
So here’s a quick overview of RawTherapee in action.
RawTherapee’s Digital Asset Management / File Browser
RawTherapee doesn’t use an integrated database in the way that some other apps do (eg. Lightroom, Capture One, Darktable). Instead, it uses the computer’s native file system through a file browser. In other words, you see the structure of your hard drive.
Some users prefer the simplicity of that approach. It is very much the what-you-see-is-what-you-get method. It’s also quick–there’s no separate importing step. But it’s also more limiting in that it doesn’t give you the same powerful features that come from using a database. There are no smart collections, for instance, or advanced sorting and filtering options. And an image can be in only one place; you can’t have an image being in both a client collection as well as a camera-type collection. If you’re accustomed to features like Lightroom’s Publish Services or Collections, you’re not going to find those here.
A positive benefit of relying on the computer’s native filesystem is that cross-compatibility is straightforward. And if you’re wanting to combine RawTherapee’s RAW image processing with more powerful digital asset management features, a good place to start is to use RawTherapee in tandem with digiKam (which is also open source and free).
RAW Image Processing / The Editor
RawTherapee’s strength lies in its RAW processing. And in this area, it gives exceptionally fine-grained control over individual settings.
Feel inclined to adjust specific RAW processing parameters? Then RawTherapee has got you covered. It goes way beyond basic exposure and white balance and cropping.
But while the settings are sorted under type headings (for example: Preprocessing, Raw White Points, Demosaicing, etc), there’s very little guidance beyond that. If you’re trying to choose which demosaicing method to use from the fifteen or so options, you’re going to have to research them separately (or, I guess, try your luck through trial and error). That’s a theme that runs throughout RawTherapee: there’s not much in the way of a helping hand here. If you’re near the top of the learning curve, you’ll appreciate the power at your fingertips; but if you’re near the bottom of the very steep learning curve, it’s likely to be daunting.
And that directly relates to another important issue: workflow. There are functions for saving processing profiles to reuse later and for applying settings from one image across multiple others. But RawTherapee’s strength is in milking every last drop out of an individual RAW image, not in workflow-enhancing provisions. Photographers who routinely work with large numbers of images and on deadlines will likely find RawTherapee slow to work with (and that’s aside from the sluggish performance I’ve experienced).
It’s also very limited with respect to plugins. It is technically possible to add Gimp as a plugin, for example, but that’s about the extent of it. Lightroom has a whole universe of third-party plugins and presets; there’s nothing like that for RawTherapee.
- Excellent RAW image processing
- Deep access to processing settings
- Cross-platform (Windows, Mac, Linux)
- A steep learning curve, with little in the way of in-app guidance
- No built-in database and limited digital asset management tools
- Can be sluggish on some computers
- No plugin architecture
RawTherapee excels in having very powerful and very granular image processing tools built-in. It gives you a lot of control over how the RAW images are edited and processed, making available individual settings that aren’t directly accessible in something like Lightroom.
But that comes with a big caveat: RawTherapee is not especially user-friendly. If you’re technically inclined and well-versed in imaging jargon, you might enjoy having such fine-grained control over individual settings–you can geek out to your heart’s content to milk every last drop of image quality out of your RAW images. But for everyone else, it’s likely to be intimidating and difficult to use to get the results you want.
I also found it very slow on my computer. 
I have no complaints about the RAW processing engine itself, and I’ve been able to get output results I’m happy with. But it’s just harder to do and much slower to work with. And that’s compounded if you’re working with many images at a time.
If RawTherapee stood alone, it would be a very good free alternative to Lightroom. It’s impressive that such a powerful program even exists without the incentive of monetary profit (the same could be said of something like GIMP).
But the catch is that it doesn’t stand alone. There’s another free and open-source alternative that, at least to my mind, is better: Darktable. And I suspect that most users would find Darktable faster, easier to use, and ultimately more powerful.
But it sure is nice to have multiple options available to choose from. And, since they’re entirely free, there’s nothing lost in trying them out for yourself to see whether they’re good fits for your workflow and preferences.
You can download RawTherapee here.
- It started life in 2005 as a project by Gábor Horváth and was open-sourced in 2010.
- I’m using it on a 6-core 2019 iMac with macOS Monterey and 72GB of RAM.