Just about a year after releasing darktable 3.6, the darktable team has announced darktable 4.0.0. The update celebrates 10 years of darktable offering photographers open source raw image editing. The major release adds many new features to the open source photography workflow app and raw image editor, including color and exposure mapping, filmic v6, guided Laplacian highlight reconstruction, a new perceptually uniform color space, revamped user interface, performance improvements, and much more.

Color and exposure mapping comprise a new feature in the 'exposure' and 'color calibration' modules that allows you to define and save a specified target color/exposure for the color pickers. You can match any source object against an arbitrary target color. You can use this tool to perform white balance adjustments against non-gray objects of known color, or ensure consistent color across a batch of images.

Filmic v6 includes a new color science. Darktable writes, 'This change removes the mandatory desaturation close to medium white and black and replaces it with a true gamut mapping against the output (or export) color space. This allows for more saturated colors, notably in blue skies.' Darktable 4.0.0 now includes a 'fully-sanitized color pipeline' from input (color calibration), creative changes (color balance RGB) and through to output (filmic v6).

Within the 'highlight reconstruction' module is a new 'guided Laplacian' method. This uses a 'multi-scale wavelet scheme to extract valid details from non-clipped RGB channel(s)' and 'propagates the color gradients from neighboring valid regions using edge-aware color diffusion.' The team writes that this feature promises to limit color bleeding through edges, such as green leaves bleeding color into a reconstructed blue sky. This method is only available for images captured with a Bayer sensor, so Fujifilm X-Trans users are out of luck here.

Darktable 4 introduces the darktable Uniform Color Space 2022 (darktable UCS 22). It's a perceptually uniform color space built using psychoperceptual experimental data that was gathered for artistic saturation changes. What's this actually mean? Darktable UCS 22 ' uses a brightness-saturation scheme that compensates for the Helmholtz-Kohlraush effect (accounting for the contribution of colorfulness in perceived brightness) and allows an efficient gamut-mapping against pipeline RGB at a constant brightness. It will make the saturation control in color balance RGB better behaved.' You can learn a bit more about the Helmholtz-Kohlraush effect in the latter half of the video below.

The user interface has been completely revamped to improve the overall look and consistency. Padding, margins, color, contrast, alignment and icons have been reworked throughout the application. Collapsible sections within modules have been redesigned to improve functionality, plus channel mixer RGB, exposure and color calibration modules include new collapsible sections. The vignetting module has been split into two sections. Superfluous sections have been removed in 'crop' and 'white balance' tools. The default theme is now Elegant Gray, which is the recommended choice of the darktable team.

The app's performance and OpenCL settings have been optimized, so performance is more tunable by the user and should be improved overall. There are many more other changes, including a color glossary, new contrast parameters, a new 'collection filters' module, improved search, improved export options, improved shortcuts when using sliders, a new raw exposure function, and more. Plus, there are many new bug fixes in the latest update. For the full details, visit darktable.

Darktable 4.0.0 is available now for Linux, macOS and Windows. At that link, you can also download the software's source code. If you would like to give darktable 4.0.0 a try but don't know where to start, there's a very detailed user manual available here.