Working with Darktable Open Source Image Processing
Darktable is my favorite photo management and processing application. The list of available modules can be a bit overwhelming, but I’ve identified about a dozen modules to use on most images along with a brief description of their function. First, you’ll want to select the best images from your shoot then apply the modules as listed. The default settings on most of these modules will work. Don’t be afraid to fine-tune by making small adjustments. In the end, it comes down to what’s pleasing to your eyes.
White Balance: It’s best to use the appropriate white balance setting in your camera when you shoot so you won’t have to balance all your images later. If all your shots aren’t taken under the same light some post production adjustments will be needed so your final results display consistency.
Lens Correction: Darktable will usually detect what camera you’ve used although you may need to specify the lens. It does a remarkably good job correcting visual and color distortions, such as the fisheye effect from a wide angle lens.
Orientation: Simply switching between landscape or portrait.
Crop and Rotate: Self explanatory.
Vibrance: Adds a little subtle punch to the image.
Shadows and Highlights: One of the coolest features of dt, it helps equalize the image by boosting dark areas and attenuating over-exposed areas of the image. Default settings usually work, but this can be fine tuned so the image doesn’t look over-processed.
Local Contrast: As the name implies, this improves contrast between adjoining areas of the image and improves perceived sharpness of image. Just like the above, the default settings usually work, but this can be fine tuned.
Levels: I personally prefer this module over ‘exposure’ for adjusting overall image brightness, contrast and midrange.
Sharpen: Not all images need this and care should be used to prevent loss of subtle detail. This module can, to a small degree, help with an image that is just slightly out of focus.
Velvia: Similar to vibrance, this module can add some extra punch to an image. Or as I call it, the Calendar Photo effect. You know, where an image has a bit more color saturation than it appeared in real life.
Denoise (bilateral filter): Of the four de-noising filters I’ve found this one works best. Adjust the RG&B sliders up until chroma noise is sufficiently reduced without blurring the image too much.
A note about Input and Output Color Profile: These modules always appear by default. I recommend leaving them set to sRGB and set your camera and monitor to sRGB as well. This way all devices through the work-flow are set to the same color standard.
Below is an example of an image before and after applying the above modules. The original turned out pretty good on it’s own, so I should find a better example of before & after. Most visible is the slight correction of lens distortion. .
More about darktable along with detailed user guides are available online at darktable.org.
This guide and photographs prepared by Kenn Ranous.
PS: A few notes made while experimenting: your results may vary.
1. Shoot using the lowest ISO setting to minimize noise.
2. Turn In-Camera noise reduction off and apply those filters in post-production. You can also create a black frame shot with the same shutter time (cover the lens AND the viewfinder), then add that as a subtracting layer in Gimp later. This achieves the same thing in-camera noise reduction does but gives you control of the final blending.
3. If you can get the shot properly exposed and white balanced in the camera, you can get the same quality using jpg mode as raw. This saves a lot of time and disk space later.