DMV – Darktable Modules Visited
Darktable is an Open Source Photo Manager and Editor for Linux similar in function to Adobe Lightroom. If you’re new to Darktable, you’ve probably noticed how many modules there are and wondered what they all do. This application is pretty well documented, the User Manual is available at darktable.org and it’s a good reference.
Sometimes it’s hard to describe their function with words so I ran through all of them with a few of my favorite images and compiled a list of the ones I find most usefull. The default settings work in most cases and the closer an image is to having ideal lighting and exposure, the less effect most modules will have.
As far as I know the net results are the same regardless of what order they’re applied. Nonetheless, and probably more out of habit than science, I usually do it in this order:
Lens Correction: Corrects lens flaws such as distortion and vignetting. It’s very effective at fixing fish-eye, although sometimes that’s a desirable effect.
Sharpen: Enhances the contrast around edges and thereby enhances the impression of sharpness of an image. The default settings are very subtle, but it adds just a bit of crispness to an image intended for web.
Velvia: Enhances image saturation. Its effect is tailored to increases saturation less on lower saturated pixels than on highly saturated pixels. In short, it subtly warms an image up.
Vibrance: Saturates and brings down the lightness of the most saturated pixels to make the colors more vivid.
Local Contrast: Boosts the details of an image for greater contrast and clarity.
Shadows & Highlights: Independently adjusts the darker and lighter parts of an image. It can restore details lost by over or under exposure. Sometimes an almost HDR-like effect can be accomplished by bringing up the shadows and lowering the highlights, and shooting RAW will definitely give you more headroom for recovery. In some cases the resulting image can look over-processed, so occasionally minor adjustments of the modules settings are needed. By using more extreme settings, this can be a very creative module as well.
Crop & Rotate: Self-explanatory, great for fixing slightly skewed images and tightening up the framing. I always try to get this right in-camera, but if I get a bit too much sky in a nature scene I just crop an inch or so off the top and viola, a wide-screen scenic image. If I’m a degree off-balance when not using a tripod, also easily fixed.
Levels: Works just like levels in any image manipulation program by adjusting black, white, and mid-gray points. Used in conjunction with a historgram, this tool is a cornerstone for image correction. I apply this module last as Local Contrast and Shadows & Highlights fix most exposure problems.
White Balance: I don’t personally use it much because I’m very particular about using a preset or manual white balance when shooting. Trying to get uniform white balance across a set of images shot using auto white balance can be a tedious process. If the color temperature changes significantly throughout a set, (ex: A large room with light from various sources), then some post-production tweaking is needed. Adjustable parameters are tint, temperature, red, green and blue.
A list of the modules and histogram for the example image.
In this image you can see the before & after results of applying the above modules. It brought up the shadows, fixed the lens distortion and improved detail and clarity. Unfortunately the sky is blown out and no detail could be recovered. This would have been a good place to do an HDR, or at least shoot RAW for a little more headroom to make recovery, but at least I saved a decent photo out of it. Which is good, because this was a memorable place I may not be getting back to soon.
In summary, I always try to get the image as correct as possible in-camera. I like to use manual settings (or presets if time is short) and a tripod in lower light situations. Experience in selecting scenes helps. In practice, it often takes a few post-production tweaks make images more pleasant to the eye. It all depends what you’re desired final result is: Subtle and natural versus eye-popping calandar shots or somewhere in-between.
Thanks for l00kin!
– Ken Ranous
Best open source photo image manager editor for Linux, Mac, Solaris.