Sure,
Thanks Houz for referencing that. I read this article, and it is really helpful for processing HDR EXR files. If I’m not mistaken, EXRs contain masks, unlike exposure fused DNG file. However, of course, regardless of the differences, after I failed to save the colors while bringing up the contrast effcetively with the Tone Curve, my initial guess was to try the Global Tonemap (genuinely HDR tool), but it produced poor results taking all the histogram chart to the right, with the adjustments having no significant effect. Then I tried the Tone Mapping module which gave, to my taste, better results, thouigh still it failed to keep the colors.
I might be doing something wrong or lack knowledge of proper modules application, but, while there is a vacuum in this topic, please forgive any of my faults should you find them.
Also, thanks for the DT Blog updates, there is also a good article on using the Lab curves Mastering color with Lab tone curves | darktable
that brings a light onto adjustments within the Lab colorspace
Apples and oranges. Conventional HDR does what DT’s HDR does, it just does it using demosaiced source images.
The lovely photo shows a low dynamic range scene. The histogram proves it. One gains nothing by putting it in a high dynamic range container. The dynamic range you got out is the same one you put in. With such a low dynamic range scene, you might as well save yourself time by using only the brightest of the three images.
One is made from the “HDR”, the other is made from only the brightest of the three:
The only thing making a HDR in this case accomplishes is that it kills the horse who wouldn’t stand still.
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Nice, can I see your modules history for the DNG?
I tweaked around with the masks and reduced the haze to more pleasing level while retaining the colors
Here’s how I did it http://i.imgur.com/jYdQIS3.png
So, what workflow procedure would you recommend? It is more interesting to figure out right sequence of modules than just getting this very image processed. I used this sample image just as an example of contrast and color issues one might face working with DT modules
And, of course, thanks for the advice on HDR procesing essentials 
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Processing photos costs me enormous mental effort because I’m faced with countless possibilities and I’m incapable of choosing just one 
I love it, but it’s also exhausting.
I download files straight to /tmp (RAM), so when I closed my RT laptop I also lost the download and the sidecar file. When I’m back on that laptop I’ll see if it’s in the cache; if it is then I can share it with you. The absolutely only parameter difference between the “HDR” and the normal image is that I had to adjust the exposure in one to match the other.
The haze. I used to fight such things, now I just go with the flow. Maybe one could get rid of it in post-proc (Retinex in RawTherapee and luminosity masks in GIMP come to mind), maybe it could be even done to look realistic, but it was there, it gives the photo its look, so embrace it.
…Though now I am tempted to try removing it, just for kicks 
Dealing with real high dynamic range scenes is not simple. Endless possibilities. Sometimes curves alone work great, sometimes they’re not enough. Sometimes tone-mapping works, sometimes not. Sometimes you have to dodge and burn and use luminosity masks. There is no one-size-fits-all. Maybe with another 30 years of experience I’ll be able to offer some advice, but not now.
Well, yes and no. EXR files can contain a lot of things, like masks, depth data, other color channels, reflectance data, … However, most often EXR is just used as a HDR capable container when used for stacked image sequences so none of those extra features are used.
Sure, combating haze is very selective thing to do in photography. I bet the haze would can never be eliminated with a tool that operates in one click. What I see from posts of commercial software users about about recent De-Haze plugins, they are not happy as the tool either overkills or underperforms. So, as one can see, it is unworthy to evaluate all cases algorithm.
Likewise, solely the Tonal Mapping does not do the job. It kills colors while brings the contrast up.
For HDR stacks development and mostly artifacts that, usually, follow them, such as low contrast in shadows or highlights due to wrong exposure or faulty exposure selection, I believe it is viable to find a solution. It would be great to evaluate a sequence of actions to take control of trimming down the unwanted tonal range without crushing the colors.
Here’s what I managed to attain with the Levels+Masks VS the best I could with the Tone Mapping.
The left bright side is the Levels+Masks adjustment VS the right dull and washed out Tone Mapping result. Look at the colors, can you see the difference ? Wouldn’t be great to figure out a better workflow ?
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P.S. Hence with the Levels+Masks way I yet made no contrast tweaks, just slided the margins to the histogram.
Sorry to resurrect an old thread but I’ve just found the Haze module in my darktable 2.3.0 ~git647, not sure how long its been there! Just been playing around with it at normal settings. Its quite impressive, especially on reflections and sky. Going to look for some landscape shots to try it out (I don’t normally shoot landscapes). Well done darktable!
I realize this is a darktable topic, but on the subject of haze I’ve added a G’MIC filter to make the brightness even across an image. That can make it easier to work with contrast afterwards - it’s like a partial de-haze. If you have G’MIC it’s under testing → garagecoder → “normalize brightness”.
The premise is simple: apply a local area tone curve to push the local average towards the image average (or a desired average). No doubt there are many better algorithms out there but at least it’s reasonably fast.
The above is from your last jpg posted, default settings.
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@garagecoder, what do you think about your “Tone enhance” filter to dehaze? I think it is also a nice dehaze filter.
Yes, I’ve noticed “tone enhance” can be used that way - although probably more for the detail/sharpening part. Getting the brightness correct with it can be tricky and I suppose not a lot different from manual tone curves. It makes use of bilateral filter which can be a bit slow, not that I think it’s a bad filter
One advantage of the above is it could be easily implemented in other image software that has a guassian type blur - not that I expect it to be any better than what’s already available! It’s just an experiment made in a few minutes before work
@garagecoder, your new filter is very useful as it is. Thank you. This filter can also be used for color correction with rgb, lrgb, cmy and cmyk. (as with retinex-filter) I tested this. Sometimes with great results. In some cases it deals even with colored haze. It depends on the right color space, also a bigger area is sometimes needed. But I understand you didn’t ad this functionality, because it is not straightforward and gives, with the wrong color space, very bad results. But maybe it is an idea to play with for other (new) filters? I see you did already something with balancing in your other nice new filter “Auto balance”. Also thanks for this filter.
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The calculation is:
X represents the set of input image pixels, N the new output
L is the Lehmer mean of the image (p is used to adjust brightness, default 0 i.e. harmonic mean)
G is a gaussian kernel centred around each pixel
A is the resulting per pixel map used to apply the tone curve (i.e. the final step N)
The input range is assumed to be 0 < i < 1 because of division by zero (I just add a small value) and if normalizing at the end it doesn’t matter too much.
Not the best explanation I know but perhaps it’s of use to somebody!
Edit: yikes, forgot to actually use the h term… updated
Hi there, these are my tried and true steps for HDR Darktable, after combining the CR2 RAW images into DNG.
I am primarily processing Real Estate images, and have found HDR to be too cartoony, until I developed these steps IN THIS SPECIFIC ORDER. Now they pop.
Kane’s Darktable HDR Workflow
- First go to original, start there to remove all automatic modules
- Apply Chromatic Aberrations
- Set White Balance (using spot) if you can, otherwise do later
- Set Base Curve to Canon EOS preset or Canon EOS like alternative (thats specific to me)
- Raise Exposure, likely lower darkness. Will need to readjust later
- Global Tonemap – play with sliders to lighten, raise detail to 90-100%
- May add another instance and use uniform softlight blend, reduce opacity for color
- Local Contrast – play with detail slider and contrast (also try opaque softlight)
- Tone Curve – raise middle a tad, reduce clipping on right
- also separate instance – increase green (drop “a”), increase blue sky (drop “b”)
- Shadows and Highlights, mostly default, check radius, compression, check gaussian vs. bilateral
- Highpass and Lowpass, I have presets, usually uniform softlight, adjust sliders, opacity if needed
- Lowpass saturation is set to zero
- Now fine tune, etc., crop, velvia, graduated density for sky, etc.
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The order really shouldn’t matter. That being said, do you have some example? I am always curious to see the actual results. 
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