Raw photo editing with RawTherapee

Superficially, RawTherapee looks a lot like darktable. The initial view is called the "file browser"; like darktable's "light table", it allows the user to import images into the application, add star ratings, and choose an image to edit. There are options to filter images in a number of ways, including by aperture and shutter speed, or by the lens that was used to take them. The right sidebar can also be turned into an inspection window for quickly looking at images using a 1:1 pixel ratio to check for focus.

As an experiment in processing photos with RawTherapee, your editor used the file browser to choose the image shown below, taken on a recent outing above town. Once again, this photo is anything but a great work of art, but it does show the kind of problems that a raw editor can address. The image contains a lot of contrast, and the mountains in the background are somewhat overexposed — an ongoing hazard when photographing scenes with snow in them — while the foreground is dark. What is shown here is the image as produced by the camera; what can be done to improve it?

The editor window will also look familiar to anybody who has seen darktable, with the image being edited taking the center part of the screen. The left column contains a "history stack" tracking image operations and allowing them to be undone, along with an overall image view and the color histogram. On the right is a set of tabs providing access to the many things that can be done to the image.

Certain aspects of interaction with RawTherapee can be annoying at times. It seems necessary to repeatedly remind the application that it would be nice to see the whole image at the largest size that fits within the window, for example. The "crop frame" tool (which, for whatever reason, lives above the editing area rather than with the rest of the cropping controls) makes it easy to draw the frame, but a naive attempt to move the frame drags the whole image within the window instead. To move the frame, the user must hold down the shift key, which is not readily discoverable without going in and reading the manuals. It's all stuff that one can get used to over time, but it slows down the process of learning how to use the tool.

One other, highly subjective impression is that RawTherapee is relatively slow to carry out its operations. Many changes are accompanied by significant delays in a way that happens less with darktable. To compound things, it is not always obvious when RawTherapee is working, so one ends up wondering if an intended change simply had no effect, or instead the application just hasn't managed to show it yet.

On the other hand, the two-pane (shown below) view helps the editing task considerably by making it easy to see the image both before and after a set of changes. A set of tweaks that may seem like a good idea on their own may look different when compared to the previous version of the image. There is also a "snapshot" capability that can be used to save the state of the work at any point.

This is as good a point as any to mention that, like darktable, RawTherapee is a non-destructive editor. The original raw image is never modified; instead, a list of changes is saved to a "sidecar" file and played back as needed. It is nice to know that there is nothing one can do in the editor to wreck the original images — other than deleting them outright in the file-browser view, of course.

Back to editing

RawTherapee does an interesting thing when an image is first pulled into the editor: it tweaks a number of settings to make the image look as similar as possible to the one produced by the camera itself. This includes obvious adjustments like setting the white balance to the value selected by the camera; just about any raw editor will do that. But RawTherapee also, according to the documentation, scans the JPEG image that the camera creates (and stashes inside the raw image) and sets its tone-mapping parameters accordingly. The documentation also says that this process may fail, though your editor did not see that happen. It does help to bring up the editor in a reasonable starting state, especially for users who are not deeply familiar with the process of processing raw images.

Darktable has its "pixelpipe" abstraction with processing modules that can be added and removed in any order. RawTherapee takes a simpler view; it provides an extensive set of processing options, but there is no visibility into (or control over) the order in which they are applied. It is not possible to apply any given process more than once. For a raw-editing neophyte like your editor, this is likely to make little difference, but it does feel like a less flexible system.

Editing a raw image follows the usual steps, starting with setting the white balance and exposure levels. The pointer can be used to set the white balance by clicking on a white (or neutral gray) pixel in the image; taking pictures with snow in them helps greatly with this process, so you editor suggests including some snow in all photographs. This mode remains active thereafter, though; it is easy to click on some other part of the image later on and throw things far out of balance. That is a bit disconcerting the first time it happens, but is also easily recovered from.

From there, most of the expected processing operations are available and can be turned on as needed. These include adjusting the tone mapping, playing with contrast and saturation, sharpening, perspective adjustment, haze removal, and much more. The tools all have lots of options that can be tweaked, naturally; it can be a bit overwhelming at times. Some changes can require going back to rethink decisions made in the earlier steps; it is not always clear when adjusting one operation will have effects on the others. Raw editors, it seems, all require a certain amount of time and dedication to learn how to use them well.

One feature that RawTherapee lacks is the ability to limit the operation of tools with masks. The flexible mask mechanism in darktable makes it possible to apply different processing options to different parts of the image. One might well argue that one should employ a more advanced image-editing tool for such tasks, leaving the raw editor to focus on the specifics of processing raw images. But there are times that this kind of flexibility is useful.

For more run-of-the-mill tasks, though, RawTherapee can get the job done relatively easily. Your editor pulled in the image above, tweaked the white balance slightly, changed the tone mapping to bring out more detail in the trees, applied a haze filter, and cropped the result to end up with the image to the right. This picture is still not a great work of art, but it does show why one might want to work with raw images rather than accepting the camera's idea of what the best picture would be. Turning a raw image into something that can be displayed on a monitor or printed involves throwing away a fair amount of information; the camera may not always make the right choices about what is important and what is not.

Community and conclusion

RawTherapee is mostly written in C++; it uses the the GTK toolkit for its user interface. The most recent release is 5.8, which came out almost exactly two years ago; the project has seen 2,264 commits since that date. This project is moving more slowly than darktable (8,357 commits and several releases in just over two years) and seems to be getting slower over time (only four small commits in 2022 as of this writing), but it is still somewhat active. Its developer base is relatively small, though; a total of 35 developers have contributed since 5.8, and one developer, Jacques Desmis, contributed 1,412 (62%) of the post-5.8 changes.

Whether things will pick up is not at all clear. This GitHub issue, opened in February 2020, reflects an ongoing desire to get a beta 5.9 release out, but it never seems to happen. There does not appear to be an active leader who can put the time into pulling a release together. Desmis, the project's primary contributor, says directly that he should not be counted on to drive the project forward: "I am old (soon 75 years old) and my health is poor". Clearly, if RawTherapee is to be an active project again, somebody is going to have to step up and bring some new energy to it.

That could well happen. RawTherapee is a solid editor that is, in many ways, more approachable than darktable. It could be a solid base on which a future developer could implement a new generation of photo-processing tools. The documentation is reasonably good — a requirement for a program of this complexity. On the surface, at least, there do not appear to be severe shortcomings that would require fixing before moving RawTherapee forward.

Without some new energy, instead, this project is at risk of falling into disrepair, which would be a shame. Many photographers feel the need to use proprietary software to do their work, but it does not have to be that way; the free-software community offers a number of alternatives. But photographers who depend on their tools will be reluctant to invest the time required to master a complex tool like RawTherapee if it appears to have an uncertain future. RawTherapee seems like too good a tool to lose; hopefully some energetic developers will materialize with an interest in keeping it going.