How to realistically brighten shadows in GIMP - Mantiuk and Retinex in G'MIC

There are an infinite number of ways to brighten an image. I was testing something and happened to find that this series of steps works quite well:

Image used:


(actually I used a version with chromatic aberration, while this one has CA correction enabled so it will have better details)

  1. Open an image, this is a 16-bit TIFF:
  2. Tone-map it:
  3. Make the tones realistic using curves:
  4. Run the Retinex filter with output onto a new layer:
  5. The result is over the top.

    Reminder of what it looked like before:

    Blend in the Retinex’d layer with moderation:
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:+1: I have done this before. I wouldn’t call this realistic but it is good enough and worth sharing.

… I can’ but wait for Vladislav to appear at any moment…
BTW are those real candles?

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Yes. Everything there is hand made and hand painted.

Thank you for a nice tutorial @Morgan_Hardwood!

I also played with Tone-mapping and found an even faster way by blending Fatal et al. 2002 and Reinhard 2005 operator with soft light blend mode:

Open an image and duplicate layer:

Apply Fatal et al. 2002 on top layer:

Apply Reinhard 2005 on bottom layer:

Blend top layer with “soft light” blend mode:

Finally, make some slight corrections with the curve:

I must say, GIMP developers are doing an excellent job to make this tool really awesome!

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@s7habo I like your result more. Thanks for sharing your version.

Wow, nice idea.
I wonder how the noise is when boosting such a dark image using this method?
You probably denoised it strongly beforehand?

@McCap My impression is that the input images are already HDR or otherwise prepared (e.g., denoised) for brightening.

I also tried my hand at this. Fantastic how much one can recover. I also noticed that the camera used was Pentax K10D. That makes this even more amazing. The camera is more than 10 years old and uses a 10MP CCD sensor. If this kind of resolution we can get out of it, who needs a new one?!!


I used a bit of Tone Enhance module of G’MIC Qt and then levels and curves and in the end sharpened a bit.

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Vladislav the Poker.

The TIFF is produced from merging 5 brackets spaced 2EV apart using HDRMerge into a DNG, then I just opened that DNG in RawTherapee, applied neutral (+ CA correction in the TIFF file I uploaded, but the JPG images use a version without CA correction therefore the CA around the lamps etc) and saved it as a 16-bit TIFF. I shot this using my old Pentax K10D which is very noisy by today’s standards, and I did not enable noise reduction in RT, and despite this there is virtually no noise.

The point of this was just to show one way of brightening shadows in a very realistic way using GIMP. I did not have to use GIMP at all to do that, I could have stayed in RawTherapee (and in fact I did for the version I sent to the client). Every shadow-brightening method tries to do the same thing, but is different… “same-same but different”.

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I shot a virtual tour of the house back in 2015 using the K10D and a Samyang 8mm:
http://londonlight.org/zp/Real-Estate/House-of-Karin/

The photos were processed using RawTherapee 4.2.1:

I haven’t touched the website since ~2015 so there might be a funny smell…

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WOW really impressive and colourful, must have been a lot of work… ja ja ja those royal cats in the bed are pure elixir of relax mood =) You can tell people living there have put a ton of their time and love in the space

Personally, the problem I have with HDR is that there are so many possibilities, too many… I love ( slide like) restrictitions. And use it a lot 'cause seldom I photograph through large dynamic discrepancies but I’ll admit that not always I’m happy about the ( easiness of the) processing and results. Just so that there are no misunderstandings, this has nothing to do with any method shared here, which are super interesting; though I tend to use lum masks and “blendifs”. I guess that soon enough it would be the “norm” but I still come from the now nostalgic film era… The below is ( colour differences aside) the limit of brightness for me… to keep it “real”

 
@Wyatt_Miller … the HDR impaler

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I find it very difficult! I mean getting “some result” is easy (the above are just “some result”), but if you’re shooting something like this where the client knows the exact hue of all used paints and you have to shoot it in mixed lighting (late evening light, candles, CFT) and make sure that the end result has the right hue and chromaticity everywhere, that’s a different story.

I’ll upload the image I sent to the client next time I come across it on my backup HDD, where the hues and chromaticities do match reality.

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@chroma_ghost The problem that I have with luminance masks and blendifs is that they sometimes produce rather grainy images with some sharp tone transitions. Maybe it has to do with my lack of skill… In any case, your example isn’t as clean as the tone mapping combos, though the light is more believable.

@afre I can tell you’ve got the boxing gloves on…
I prefer it manly, also 'cause of speed, if you’re trying to slice a lemon with a machete (my case), you’d appretiate the steel gloves, furtherturtle masks can be sharp or blured, dithering may depend on method used and colour of aura, blendifs like dark beverages and huge blonde wigs, my render example has grain added and an second thought extra boost in exposure because the chicken called, cut the crap and lets have a beer!!! :beers:

Sorry @chroma_ghost. Meant to say that it is more challenging to use masking than global manipulation. In that room, tea or cider might be a more suitable beverage :wink:.

Where can i find this tone mapping option if I want to replicate these exact steps? Thanks!

In GIMP-2.9.6, Colors > Tone Mapping > Mantiuk, and Retinex in G’MIC was IIRC also in the Colors section.

I use Gimp 2.9.7 and I can’t find these tonemapping filters (except Retuned in G’MIC).