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The best open-source Lightroom alternatives

Originally posted on dpreview.

There’s no escaping the fact that if you’re looking to process your raw photos, Adobe’s Lightroom Classic is the 800-pound gorilla in the room. But in addition to its raft of paid rivals, did you know that there are quite a few open-source alternatives available completely free of charge, some of which actually predate Lightroom’s own existence?

For this article we took a look at five of the most widely-recommended, open-source Lightroom alternatives, and herein present our results: the three nearest rivals we could find, plus two apps we wanted to love but which left us heartbroken.

What is open-source software and what does it mean for you?

Not familiar with the open-source software movement? Simplifying greatly, the open-source community creates and maintains software as a labor of love and a gift to the community. Not only is open-source software free to download and use, but the underlying source code is also available to modify yourself, should you have the requisite skills. Of course most of us lack those skills, but that doesn’t mean we can’t take advantage of the wonderful work of those who do.

Like anything free, though, open-source software can span a very wide quality gamut. Some apps are much more actively-maintained than others, and some have much stronger and more supportive userbases. At their best, open-source creations can provide an impressive level of quality, and can even prove more responsive to user-reported bugs and shortcomings than commercial software, which largely shuts end users out of the development process altogether.

Like anything free, open-source software can span a very wide quality gamut. Some apps are much more actively-maintained than others, and some have much stronger and more supportive userbases. At their best, open-source creations can provide an impressive level of quality.

But being unpaid works of love, open-source projects sometimes also suffer issues with developers who may, over time, decide to move on from their creations, as well as with infighting between developers that results in rival versions of the same program – known as forks – appearing to compete with each other.

With all of that said, the open-source software movement continues to thrive. Indeed, these days much of the commercial software we spend our hard-earned cash on builds upon the work of open-sourced developers. The famous Linux operating system, for example, underlies Google’s Android OS, and not only does it compete head-on against commercial rivals, it’s actually the dominant OS in its space.

Clearly, open-source software is capable of big things when done right. So, can it defeat the likes of Adobe’s Lightroom Classic? Let’s roll up our sleeves and take a look!

RawTherapee: Vast control over your images, but needs a long-delayed update to really shine

License: GPLv3
OS: Windows, MacOS or Linux

RawTherapee 5.8’s user interface in Editor mode.

RawTherapee made its debut in 2005, but it wasn’t until 2010 that its original creator, Hungarian PhD student Gábor Horváth, open-sourced the project. Initially started as a hack of Dave Coffin’s dcraw, it is still based on that open-source and platform-agnostic command-line raw converter to this day. But since dcraw itself hasn’t been updated in four years, the dcraw support is nowadays supplemented by custom code to deliver improved image quality and broader camera support.

There’s no overall image database used here, equivalent to a Lightroom catalog; instead RawTherapee stores its edits in sidecar files you place on your drives. Raw support is surprisingly good, as long as your camera is more than a few years old. Even tricky sources like Fujifilm X-Trans and Sigma Foveon sensors are supported, as well as Canon’s Dual Pixel Raw and the resolution-enhancing multi-shot modes from Olympus/OM System, Pentax, Sony and others. There are some omissions, though; for example, I discovered that images from my Canon T8i and SL3 had issues.

While the development pace is also fairly good – there are typically 2 to 4 updates per year – things have been stalled ever since the start of the pandemic. However, a major release is coming soon, that should bring Raw support up to date along with a backlog of new features.

RawTherapee also includes support for lens corrections, which can be achieved in a couple of different ways. Firstly, if your lens is supported by the third-party Lensfun library, then lens defects can be corrected automatically. Alternatively, if your camera corrects lens defects before creating the preview embedded within the raw image, RawTherapee can detect and mimic that correction during raw conversion. I found that the corrections worked pretty well, although it failed to detect the lenses built into multiple fixed-lens cameras I tried, even though they’re supported by Lensfun.

Image quality comparison: RawTherapee vs. Lightroom Classic.
Click here for the full RawTherapee image or here for Lightroom Classic.

Although there’s no overarching “Auto” function in RawTherapee, it will attempt to match the tone curve of the embedded preview, and I found that my images mostly showed reasonable exposures and good color by default, with plenty of detail, too. And there are a truly staggering number of manual controls with which to adjust your images. Thankfully, there’s also very good (and multilingual!) documentation available on the RawTherapee website.

So what are the weak spots? The user interface can be pretty intimidating with so many tools on offer, some of them with names like “Retinex,” “Wavelet Levels” or “Impulse Noise Reduction” that may leave you scratching your head. As of the current release, there are also no local editing tools, although these are promised in a future release and available already in a third-party fork called ART.

There’s also no support for camera tethering, and no map view for geolocation fans. You can only export raster images too, so there’s no support for printing, slideshows, and book or web gallery creation. If you find yourself using these functions of Lightroom much, you’ll miss them here.

I also found overall performance to be quite modest, with RawTherapee taking around 3.5 to 4 times as long as Adobe Lightroom Classic to render final versions of my images. But if you’re willing to live with the sluggish speed, and put the time into learning how to use it, there’s no question that RawTherapee is a powerful and stable tool capable of delivering great results.

Darktable: Swift, powerful and very actively-developed

License: GPLv3
OS: Windows (with limitations), MacOS or Linux

Darktable 4.0.1’s user interface in Darkroom mode.

The main open-source rival to RawTherapee is Darktable. Created by another PhD student, Germany’s Johannes Hanika, it hit the scene in 2009 and has averaged an impressive 6–8 updates per year ever since. (It’s also the only application considered for this roundup that has never gone a year or more between releases.)

Darktable’s biggest selling point for me has to be its proprietary RawSpeed processing engine. It isn’t used for every camera – if a given model isn’t supported by RawSpeed, Darktable will fall back to relying on a newer dcraw fork called libraw – but for supported cameras, processing performance is well over double that of RawTherapee. Sure, it still takes about 2/3 longer than Lightroom, but at least it’s in the right ballpark.

Like its rival, Darktable has surprisingly good, multilingual documentation, but it goes one better by also offering up a lengthy list of supported cameras. While RawTherapee is totally reliant on sidecars, Darktable stores your edits in a database and uses sidecars only as a supplemental way of communicating its edits to third-party apps. (If these apps make a change to the sidecar outside of Darktable, though, it won’t be read back in and will be overwritten by its next edit.)

Lens corrections are also supported, again via the Lensfun library so the list of supported lenses should be much the same. I did, however, hit one image from a Panasonic FZ1000 II that worked fine in RawTherapee but which Darktable would close every time I tried to open it, and which would cause its processing batches to fail if included.

Image quality comparison: Darktable vs. Lightroom Classic.
Click here for the full Darktable image or here for Lightroom Classic.

At the same time, though, it happily read several images from the Panasonic ZS70, Canon T8i and Canon SL3 which RawTherapee had some issues with. And while Darktable did an okay-ish job of rendering images at default settings, it tended to yield softer, darker and more muted images than RawTherapee out of the box.

But while in my opinion most images needed some minor tweaks to luminance and saturation, not a single one was miles off, where RawTherapee was multiple stops out on the ZS70 shot’s exposure, and rendered the T8i and SL3 shots with extremely low saturation.

Overall, neither app is clearly better than the other in terms of camera and lens support. The good news is that since they’re free, you can try both applications on your own gear with no more expense than your own time.

There’s a noteworthy difference between the two apps’ features, at least if you’re a MacOS or Linux user, as Darktable offers printing and tethering functionality on those platforms – sadly, the Windows version doesn’t get them. And while all versions also include a map view for geotagged images, I found that this crashed the app every time I opened it. (Darktable also crashed for me once in the slideshow tab, but was otherwise stable.)

All of its extra functionality makes Darktable a more realistic alternative to Lightroom than RawTherapee (especially for Mac and Linux users). But that’s not to say everything’s completely on par.

The really big feature is available regardless of platform and works just fine, though. Unlike RawTherapee, Darktable’s current release allows not just global, but local editing. In addition to dust and spot removal, you can create hand-drawn or parametrically-generated masks, combine the two, and create raster masks.

And while for global editing there aren’t anywhere near as many tools on offer as in RawTherapee, all the basics are there to give you plenty of control over your images. They also mostly have more intuitive names, and there’s a search function to help you locate the tools you need.

All of its extra functionality makes Darktable a more realistic alternative to Lightroom than RawTherapee (especially for Mac and Linux users). But that’s not to say everything’s completely on par.

As well as the omitted tethering and printing functionality on Windows, Darktable forgoes Lightroom’s ability to create photo books and web galleries. And while it does have a slideshow tool, this only runs locally and can’t export a shareable slideshow. Nor is there any overall Auto function to get you in the ballpark, although some individual tools do have auto modes.

LightZone: Promising, but development and support lag its rivals

License: BSD-3-Clause
OS: Windows, Mac or Linux

LightZone 4.2.4’s user interface in Edit mode.

Where RawTherapee and Darktable started off as side-projects for PhD students, LightZone had a very different genesis. Originally launched as a commercial app exclusively for the Mac in 2005, it was withdrawn from sale by 2011. A year later, its developers decided to release the fruits of their labors to the open-source community, who’ve since expanded its reach to Windows and Linux computers as well.

But while historically it’s been one of the top three open-source Lightroom alternatives for years, of late it seems all is not well for the project. It was never the most active, with typically as few as 1–3 updates per year. But for the past two years, we’ve had only one update apiece (ignoring a very minor Mac-only bugfix).

And alarmingly, the project’s website – still linked to from both the app itself and its github page – vanished in the first few months of 2022. Development also seems to have completely stalled, with not a single commitment made to the project since mid-June.

With the website offline, there’s no official documentation beyond the included (and rather dated-looking) help file linked from the program’s Help menu. And even before it went offline, the website offered only an ancient tech wiki for “LightZombie” (the open-source project’s name in its early days), which hadn’t been updated in about a decade.

Image quality comparison: LightZone vs. Lightroom Classic.
Click here for the full LightZone image or here for Lightroom Classic.

Still, despite the program’s user interface feeling a bit dated too, I soldiered on, as its key “selling” point remains quite interesting: a spin on Ansel Adams’ famed Zone System. But where Adams’ system had 10 zones, LightZone opts instead for 16. As you mouse over each zone in the ZoneMapper tool, a preview indicates which areas of the image are covered by that zone. You can then adjust the positions of each zone compared to the others to get luminance where you need it. You can also make local adjustments based on luminance and color ranges.

I felt camera and lens support to be noticeably more limited than in LightZone’s nearest rivals, although I couldn’t locate a full list of supported cameras or lenses. Its image quality at default settings was also the weakest of the trio, with images being quite soft and the exposure frequently out by a fair way. It did a better job with saturation, but white balance was also less-than-perfect and skin tones were poor without manual intervention.

Although it is built on a combination of the raw engines powering both RawTherapee and Darktable, it’s nowhere near as swift as the latter, let alone Lightroom Classic. Performance is still a little better than RawTherapee, however.

With its lack of documentation or a website for the application LightZone was by far the least enjoyable of the three to use, in spite of its interesting zone system functionality and inclusion of local editing tools.

LightZone also has the most limited selection of global editing tools of the bunch, and lacks Lightroom features like map view, tethering, slideshows or web galleries. You can print directly from the app, though, making it the only one of this group able to do so on the Windows platform.

Also, while it never crashed on me, LightZone gave me more headaches than RawTherapee and Darktable in other ways. For one thing, unlike its rivals, it didn’t detect that my Windows installation uses controlled folder access, and I had to manually let it through Windows’ filtering before it could access my files.

It also has an issue with touchpads, in which I could scroll up and down lists or panels, but as soon as I let go of the touchpad it would bounce back to where I started. This was most troublesome with lists that extended beyond the edge of the screen, as you couldn’t even scroll with the keyboard arrow keys.

All of these issues, coupled with the lack of documentation or a website for the application, made LightZone by far the least enjoyable of the three to use, in spite of its interesting zone system functionality and inclusion of local editing tools.

DigiKam: An inability to write data was a dealbreaker

License: GPLv2
OS: Windows, MacOS or Linux

Digikam v7.8.0’s user interface in Image Editor mode.

There were two other apps that I wanted to include in this piece, but had to drop after experiencing major issues that I couldn’t resolve within a reasonable amount of time. The first of these is DigiKam, which dates all the way back to 2001 and has been actively developed for all but one year ever since.

It showed quite a bit of initial promise in terms of its feature set, which mirrors that of Darktable most closely. That said, I found it completely unable to write files to disk no matter what I tried, including manually allowing it through controlled folder access. It also crashed over and over, even when running with administrator privileges, so stability is likewise a significant issue.

Given that none of the other apps I tried had any such problems and I was using the most recent release, I had to give up on it and move on.

Filmulator: Promising, but the Organize tab needs improvement

License: GPLv3
OS: Only Windows or Linux officially, although third-party MacOS betas are available

Filmulator v0.11.1’s user interface in Filmulate mode.

The last piece of software I looked at was Filmulator, which is also the most recent of the bunch, having launched in 2017. The hook here is that its image processing, which is based on libraw, aims to mimic the look of film photography. While its global controls are the most limited of the bunch, I’d have to say its default image quality was second only to Lightroom Classic for me.

Unfortunately, though, its Organize tab was basically unusable. Its only possible view is a monthly one, with no other way to locate a photo, and every month is shown in the awkward-to-scroll list regardless of whether it included a single photo or not. (It’s particularly fun scrolling from 1970 to today if your camera’s time and date weren’t set for a shot.)

Clicking to view photos from the individual days in each month is also unnecessarily difficult, and together with its more limited editing features, I decided it’s just not a viable Lightroom rival at this point. It’s a shame, though, as with better organizational tools it could have been quite promising, especially for photographers who just want good results right out of the box.


I came into this roundup seeking a viable alternative to Adobe Lightroom Classic for those who, like me, prefer to abstain from software subscriptions, and who like to support open-source software when feasible. And while nothing I found could rival Lightroom Classic for performance and features, I was honestly a little surprised by how close some apps came.

Can any of these apps completely replace Lightroom in every way? No, but arguably they don’t need to, as most Lightroom users never touch half of what that app has to offer, something Adobe itself has acknowledged in its own attempt to replace it with the rather more feature-limited, mobile-friendly Lightroom CC. Darktable, in particular, gave me most of the features I use with any regularity in Lightroom.

Can any of these apps completely replace Lightroom in every way? No, but arguably they don’t need to, as most Lightroom users never touch half of what that app has to offer.

Compared to its for-pay rival, Darktable isn’t going to give you quite the same image quality without needing to roll your sleeves up and start tweaking, but that’s perhaps to be expected with a product entirely based on its authors’ goodwill. Arguably, though, it gets you close enough that it’s worth taking the time to learn.

Best of all, you can try it in parallel with your existing workflow of choice – be that from Adobe or one of its rivals – without having to spend a cent. If it’s not ready for your workflow yet, well…nothing ventured, nothing gained. And just perhaps, you’ll find that an open-source image editing tool gives you everything you actually need, and you can ditch those spendy subscriptions for good!

Source: dpreview

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