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short Darktable tutorial

Discussion in 'Image Processing' started by Dragos101, Sep 6, 2015.

  1. Dragos101

    Dragos101 Mu-43 Regular

    68
    May 1, 2015
    Bucharest, Romania
    Dragos
    Maybe some of you read my other topic discussing what I view as the best Raw Processor for the Olympus files.
    Many (including myself) were probably put off by the interface and the challenge of learning a new software. Nevertheless I decided to learn Darktable and found it's very well laid out, with a good manual and no features that would require to "unlearn" anything. It does have a lot more capabilities than LR, but for the basic 99% of image processing it's very simple.
    Here is a short tutorial for an everyday scenario: A picture taken in not so great lighting, harsh with challenging colors. The goal is to improve it as much as possible without ruining the mood - a sunny seaside afternoon.
    Some may object with my results which is perfectly fine, the purpose here is to show the tools which obviously some may use to a better end result.
    I start with a base conversion. This includes a contrast curve and a HSL preset that I developed by comparing several pictures with the default Olympus jpeg conversion. My goal was to start with something very close to what OV3 would produce and be able to take it much further with some modern PP tools. I'm pleased with this preset, might require some fine tuning depending on the actual scene but it works ok as a starting point. Other "default modules" are Sharpening (with a "general" preset) and Denoise, set up for slight Chroma noise reduction, similar to what LR provides as default.
    20998632760_76e5869a67_h. base conversion by Dragos Simionescu, on Flickr
    Note that the Tone curve in DT is working on Lab space, as far as I understand this gives much better control on the luminosity without affecting hue or saturation as much as the same tool in LR.
    By the way, this is me and my family, trying to get a family portrait by the sea. I triggered the camera with my iPhone while my kid was showing his enthusiasm for this endeavour. Needless to say we quickly dropped the whole idea.
    The picture definitely needs some taming of the harsh light and some selective exposure compensation. Let's get to it.
    The Highlight and Shadow module works great, maybe not as refined as LR's but still helps a lot without producing unwanted artefacts if set up correctly.
    20564074594_95b57ca1c7_h. highlight_shadow by Dragos Simionescu, on Flickr
    Now let's do selective exposure compensation - Dodging as known by the more experienced darkroom veterans.
    Virtually all effect modules in Darktable can be applied in various blend modes (similar with the layer blending in PS, with several ways to mask the effect. The masks can be brushed in, drawn, set up by parameters such as Luminance, Chroma, Hue etc, or even parametric and drawn. Let's say you want to dodge a part of the image but want to put more emphasis on a specific hue range. You choose drawn+parametric, draw your area of interest and than combine with a specific hue range. You get a mask that covers only the specified hue range from that particular area. This is a small example but it's hugely useful, and remember it can be used on basically all modules.
    For my picture I chose to do a simple drawn mask. I could've brushed it in (similar to LR) but I much prefer the selection drawing for precise results. It works really fast, just place a few clicks on the contour of the area, adjust the fall off with the mouse wheel and done.
    20998836928_927ff076b9_h. selective exposure by Dragos Simionescu, on Flickr
    And here is the end result, I also adjusted the black point for the dodged area to maintain the contrast.
    20564074434_c7ef703d63_h. selective exposure 2 by Dragos Simionescu, on Flickr
    I feel that the dodged area doesn't quite match the rest of the image mood, seems to be a bit too red. I want to very slightly correct the shadow tint. Enter the Color balance module.
    This is a simple parametric RGB curves adjustment. You can set the black and white point for each of the curves and also the gamma (how concave or convex is each of the curves)
    I simply moved the black point of the Blue curve slightly to the yellow side. This resulted in a bit warmer shadows, which I like.
    20564075074_1097dc0015_h. color balance by Dragos Simionescu, on Flickr
    I like to add some vignetting. Ever since using Aperture I fell in love with its vignetting effect, which is MUCH more attractive than any other I tried. It doesn't just darken the image's edges, it also saturates and increases contrast as the fall-off increases. I tried to simulate it here by using a curves module and applying it with an oval mask. What you don't see is the a&b curves, which are also drawn as S curves. This means the setting, besides pulling down gamma, also increases color contrast in the Lab space, creating deep saturation and color punch.
    I apply this with an oval mask, adjust the size of the mask (similar to choosing the center center point and fall-off radius) and set the opacity (similar to choosing intensity)
    21186765955_c342ecd3ac_h. vignette by Dragos Simionescu, on Flickr
    And here it is, my seaside "family photo" :) Notice how this vignette effect gently increases the "density" of the picture, not only darkening the corners.
    21186766575_8d9852ba4a_h. final by Dragos Simionescu, on Flickr

    That's it, the whole processing took me no more time than it would in LR, in fact the most time consuming part was designing the "base conversion" curve and HSL setting, which can be applied automatically for all imported images based on a simple or complex filtering setting. You can for example load a set of presets for all Olympus raws, some presets for high ISO, some for a specific lens etc. Once you set these up you don't have to do much more than loading the RAWs and start working only on the PP.
    Hope you enjoyed this, all questions and comments are more than welcome.
     
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  2. datagov

    datagov Mu-43 All-Pro

    Dec 2, 2012
    New York
    Great tutorial of Darktable. I've been using DT for about 3 years and love it. Every time I think I get jealous of all the media attention lightroom gets I discover another powerful feature of DT and realize it has everything I need.
     
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  3. sokar

    sokar Mu-43 Veteran

    392
    Nov 30, 2011
    Thank you Dragos for writing this about Darktable. I have been researching open source alternatives to LR and your post was timely. I currently use Windows and wish to move to Linux in the future to avoid being tied to adobe products. The only constraint was the PP options within Linux and how they compared with LR and other commercial variants. I must have watched 30 tutorials on Darktable in the past week and it is definitely fully featured. I agree that its feature list extends past LR. The other program that seems interesting is Pixeluvo. It is not free, but minimal cost and it appears to have the features I would use in PS.
     
    • Like Like x 1
  4. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    @sokar@sokar FYI, RawTherapee runs on Windows. It's not a DAM, but there are free options.

    Barry
     
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  5. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I use Darktable as my main editor. Sometimes the colours can be quite different from the Oly ones (skyes for example) and very hard to replicate but most of the time the default rendering is very good.
    My most used modules not already shown are:
    - Local contrast
    - equalizer: (with clarity preset (with 20% opacity) or freely)
    - denoise (profiled): for quick and easy denoise (usually setting it to a lower strength). For heavy lifting: raw denoise, non-local means and bilateral, often together.
    - lens correction: (even if some lenses are not fully recognized and have to be manually selected, like the 12-40)
    - color correction: (I never enabled the color balance and color zones, I'll give it a try)
    - zone system: I do not use it much but it is nice to visualize the zones of an image
    - monochrome: (even if I do not understand what the color map means)

    Blend uniformly is my most used mode, ellipses and gradient masks comes next (very useful the "display mask" button, a white square with a hole). And "parametric mask" limiting the input slider to shadows can be used, for example, to do heavy denoise in shadows only.

    DT has a lot of modules that by default are disabled and are hidden in the "more modules" section in the bottom right of the screen.
     
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  6. Dragos101

    Dragos101 Mu-43 Regular

    68
    May 1, 2015
    Bucharest, Romania
    Dragos
    That's one strength of DT, how you can achieve similar results using different modules, so everybody can choose the workflow that suits him best.
    I'll look and see how can I export my Color Zones profile and share it here, I think I got really close to the Oly base color.
    - Local Contrast - very powerful, similar to LR's Clarity but with more options. I just don't use "Clarity" that much because I mainly shoot portraits, but for landscapes it's great.
    - Equalizer - VERY powerful, but too advanced for my personal needs. Reminds me of a Topaz plugin, (Topaz Clarity?) in which you could specify the local contrast enhancement for all "bands" - coarse, medium, fine etc
    - Denoise - I prefer the manual non profiled module, the profiled gets kinda smudgy, while with the manual you can tweak to avoid that
    - Lens Correction - also works great, I rarely use it though, never had in any software since I don't mind some distortion and vignetting
    - Color correction - this is a mixed curves/split tones/white balance module, easy to use to do global corrections, but I prefer the Color Zones to do individual HSL tweaks, I suggest you give it a try.
    Great tip about doing noise reduction with a luminosity mask!
     
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  7. pdk42

    pdk42 One of the "Eh?" team

    Jan 11, 2013
    Leamington Spa, UK
    I installed Linux Mint in a Virtual Box VM last night (my main OS in Windows) and installed Darktable. However, Darktable just hangs silently whenever I open an image (ORF or JPG). Not a good start... Anyone got any ideas?
     
  8. Dragos101

    Dragos101 Mu-43 Regular

    68
    May 1, 2015
    Bucharest, Romania
    Dragos
    Sorry, I personally have zero experience with Linux, native or virtualized... Could it be that you don't have full access rights for the files locations when running the VM?
     
  9. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    @pdk42@pdk42, Try running DT from an X terminal window so you can see if there are any errors.
    Also, make sure the VM has enough RAM (2-4GB).

    Barry
     
  10. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    Sometimes when you open a new image and DT is already running the image is only added to the collection. You have to double click the bottom thumbnail to open it in the "darkroom".
    If instead the program is completely hung...no idea. How did you open the image? Maybe try in a different way (import, Open with, drag and drop, etc.).

    I'm running Mint 17.1 cinnamon native. I use this PPA

    https://launchpad.net/~pmjdebruijn/+archive/ubuntu/darktable-release

    to have the very latest version (1.6.8).
     
    • Informative Informative x 1
  11. pdk42

    pdk42 One of the "Eh?" team

    Jan 11, 2013
    Leamington Spa, UK
    Maybe it's because I'm using Mint and not pure Ubuntu - dunno. I have to say, despite being a Unix SysAdmin back in the days of Unix 7 on a PDP11 and having coded in everything from assembler to Java, I still find Linux a PITA to use! Too many distros, too many ways of doing the same thing, too little consistency, too much faffing around just to install something... I'm no Redmond fan, but overall I prefer Windows to Linux!
     
  12. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    This would be nice. In this picture for example:

    https://www.dropbox.com/s/grt8ebcwpbl5xmf/P8220380.ORF?dl=0

    the sky has an ugly magenta cast very different from the light blue from OV3.
    I can see from the "color zones" curve in the first screenshot that you just pushed down the purple toward the blue. And I think more lightness in the blue zone.

    Another use of parametric mask could be the desaturation of the dark parts only as suggested in a few articles to mimic the human vision.
     
  13. Dragos101

    Dragos101 Mu-43 Regular

    68
    May 1, 2015
    Bucharest, Romania
    Dragos
    Yes, one of the main corrections I do in Color Zones is the blue hue. I also hate the deep magenta sky (I think of it as Sony blue :) )
    I also noted in another thread the Shadows desaturation that OV3 does which I like a lot. I believe that the standard Darktable rendering coupled with the Tone curve mimcs that pretty good. It can also be exagerated with some parametric masks if needed.
    I also do other tricks with the parametric mask. Have you ever noticed in OV3 how a portrait even though has a pale light skin it also has bright saturated red lips? I LOVE that look and tried to replicate it here. What I did was load the Color Contrast module, bump the "a" (red/green) contrast a bit and then set up a parametric mask. This module woks in Lab so the parameters are also in Lab. Select the "a" range so you only get the reds (about the right half of the range) and then combine with the L and the Chroma ranges. Select only the desaturated reds (the left side of the C range) and remove the low luminance range so you don't bump the shadows. What you end up with is a parametric mask that selects the medium to high luminosity, low saturation, red color. Which, in case of a portrait exactly matches the lips and some areas of the face. Tune the intensity with the opacity slider (you will probably only need 30% or less). Engage it and watch your portrait come to life without bumping saturation across the whole reds spectrum which would result in an ugly "exagerated healthy" look.
    Here's my "base" preset, it basically contains the Color Zone setting and the Tone curve, it also includes a Color balance setting which may or may not be needed. I use it to slightly tame a green cast which I sometimes get with the DT conversion, compared to the original jpeg. Let me know what you think.
    https://dl.dropboxusercontent.com/u/16129394/oly default.dtstyle
     
    • Appreciate Appreciate x 1
  14. YantaYo

    YantaYo Mu-43 Regular

    92
    Apr 18, 2012
    Colorado
    Thanks for the tutorial. I downloaded DT. Does it have anything comparable to LR Dehaze or DxO ClearView? I find these tools extremely usefully for my landscape and wildlife photos. Very quickly one can add/remove haze from photographs.
     
  15. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    If you can adjust contrast for mid tones, that should be equivalent to dehaze.
     
  16. Dragos101

    Dragos101 Mu-43 Regular

    68
    May 1, 2015
    Bucharest, Romania
    Dragos
    You have the basic Local Contrast, which acts like LR's Clarity, but you can specify the coarsness of the filter. You can therefore tweak if you want just a broad mid punching or a fine structure enhancement contrast. Or you can load two instances and do both. Or you can load the Equalizer and have full access to several bands.
    I don't have LR6 so I don't know exactly what Dehaze does. It's most likely a couple of filters hidden behind a single slider, so it should be possible to implement in DT if the Local Contrast doesn't satisfly you.
     
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  17. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I try to stay in the Debian family as much as possible so most things are quite consistent. If you jump around too much...they are just different OS sharing the kernel. My experience with Microsoft things has always been a lot more nightmarish...
     
  18. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    Equalizer has a preset called clarity hidden in the micro menu in the module title bar. It is very strong but you can tune it with "mix" or blend opacity. Otherwise you can tune each curve, with a lot of patience (and save the result as a preset). Do not know dehaze enough for a real comparison.

    Another way to make a quick strong tone corrections is to work on the "base curve". I think it is a different kind of "tone curve", more low level, but sometimes it is easier to work here. If you mess things around too much just choose "olympus like alternate" preset to reset it.

     
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  19. grcolts

    grcolts Mu-43 Regular

    186
    Feb 1, 2010
    Texas
    Gary
    Thanks for posting your workflow of your family image! I have used DartTable for the Mac now for a year or so. Early editions of the program caused me many problems but now those problems have all but been eliminated and the program is a solid post-processing tool. The black & white module is simply wonderful to use.
     
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  20. pdk42

    pdk42 One of the "Eh?" team

    Jan 11, 2013
    Leamington Spa, UK
    Well, I fiddled and managed to get it working! Not entirely sure what I did - I think it was probably some Virtual Box video driver settings. Anyhow - working now. Seems a pretty nice tool with some features that LR doesn't have. Running in a VM, it's a big sluggish but it's good enough for me to play with.

    I'll work through some of the examples here. Thanks for the help all.