Darktable: a RAW-volution
By PF Staff in Influential Photo Gear on Dec 9, 2012
A long weekend is over and all memory cards are full with pictures. But now the most time consuming work just begins. After sorting all photos there is a list of RAW- files which is much too long to be fun. For processing of hundreds of megapixels I have been using UFRaw due to a good alternative under Linux. It is hard work opening every single RAW file and tweaking the controls until being satisfied. Before the next RAW file can be done, the actual File hast to be saved. The RAW-volution started when I read about the young but yet very powerful program darktable.
More than just a pure RAW converter, darktable is an open source project that covers all needs of the photographic workflow. Beside a native color management darktable handles nearly all available RAW file formats as well as lots of bitmap file formats for Import and Export. In order to manage a huge amount of pictures darktable takes advantage of a database, so it is able to react quickly on complex search queries.
The most exciting part for me is without doubt the RAW converter function, which is 100 % non destructive due to 32 bit floating point calculations. For speedups darktable supports OpenCL in order to use GPU power for calculations. Even without OpenCL enabled all actions are performed in realtime within a fullscreen interface. It is constructed in a modular way, consisting of 47 modules at the time. The user can define which modules he wants to be shown, and he also has the opportunity to flag a module as favorite in order to have quicker access. For achieving a special result most of the time there is more than one way to do it, so the user can choose.
A great similarity to other big commercial programs is obvious, but why not using proven techniques? The program operates in principle in 3 modes. In the lightable mode one can import, manage and export images. The darkroom mode is, like the name is suggesting, responsible for all Image adjustments. Remote control is also possible in the tehering mode for many camera types, but unfortunately (at the moment) not for most Pentax DSLRs (K20D is flagged experimental).
darktable in darkroom mode: you can see the snapshot function easily comparing 2 different adjusting steps, in focus is the zone system module in the tone group
So let's have a deeper look into the darkroom mode. On the right side the different modules are accessible. While one has chosen which modules to be shown, they are grouped in 7 tabs (active, favorite [configurable], basic group, tone group, color group, correction group and effect group). Even if a module is shown it can be tweaked on or of, as needed for processing (you don't need to denoise every picture, what saves processing time). Some modules are real pocketknives and control the image in various ways, while others just do one concrete job (sharpening, White Balance correction, ...). The concrete settings of most modules can be saved as presets anytime and applied later, which makes the whole adjusting process very fast
One of my favorite module is the equalizer, which allows contrast adjustments depending on the size of details. Sharpening, denoising and local contrast enhancements are very easily done. Adjusting tonal values can easily be done with the zone system module, which is much more precise than the good old curve. For image control based of colors the module color zones, with a similar unique handling like the equalizer, is my first choice. The unspectacular crop and rotate module makes it very easy to level a image, by just right- clicking and drawing a line over the leaning horizon. Every time one can zoom in to 100 % and 200 % by just middle-clicking. Furthermore a quick comparison between different adjusting- steps is possible with the snapshot- function.
|the equalizer module, here increasing
local contrast (more on huge details) and
lowering luminescence noise
|modules can be visible, hidden or marked as favorite||color zones module increasing saturation of blue
tones and lowering saturation of brownish ones
There are too much modules to cover them all in this place, but I promise there are not much wishes remaining with image adjustments (nor watermarks, objective corrections, perspective correction, cloning out sensor spots, preserving highlights and shadows, ...). So if you are happy with your picture, you can got to lighttable mode again or move on to the next image by choosing from the thumbnails at the bottom. Saving is not necessary, darktable simultaneously writes a sidecar file containing the whole history stack of the image. Consequential you don't have immediate access to a full size JPG output, only a small thumbnail to be used in lighttable mode is written to the disk. There are a few huge advantages of this method. First of all one can apply the history stock from one picture to other pictures in order to process all exactly the same way (what is pretty important when it comes to panoramic photography or focus stacking). Beside the fact that you are sparing disk space, you can alter the image adjustments every time without being destructive. Last but not least the whole history stacks can be saved as presets and later applied on images.
Final step is exporting one or more images. One can choose between different file formats and image sizes written to disk, direct export to Picasa, flickr, eMail or creating a HTML gallery. When one is exporting full size images and has no OpenCL activated, this could take some time (the longer the more modules are applied, but one can also do it over night).
The new possibilities of image adjustments alone are worth using darktable. Tough not using all features, I'm looking forward to the ongoing development of the project. At least when it comes to the quick usage and batch- converting of darktable, I seriously call it a RAW-volution in my workflow. While darktable is exporting my pictures, I lean back drinking a tea. When the magic is done, there are just a hand full of images that need to be opened in GIMP. Remember, darktable has already sharpened, denoised, rotated, cropped, added local contrast and cloned out sensor- dirt. I spare tons of hours useless work and have more time for important things like capturing pictures or drinking tea.