Evaluate the new sigmoid tone mapper just merged into master ...


  1. Neither of your sigmoid renders removes its flatness compared to filmic. Try flipping between the two in the lightbox or browser tabs. There is a “grey haze” or “less clarity” in sigmoid compared to filmic. Quotations for the loose/imprecise terms.
  2. Attempts to boost details afterward still doesn’t address #1.
  3. The closest analogy I can think of is the difference between on vs off RT capture sharpening, though this isn’t a sharpening problem.

I did the flick, in lightbox and between 100% zoom tabs. The difference I see is contrast. Filmic defaults has a more agressive toe resulting more contrast near black/less detail in shadows. Are you seeing something else?

I would agree I think… basically both can be made to be similar in many edits. I find as you say if we are talking just the defaults that filmic will be darker and more contrasted in the shadows with less detail revealed in the darkest parts and sigmoid is the opposite when it comes to the highlights as it tends to compress more … to get close to flimic it has been my experience that you have to crank up the skew and then tweak contrast. Those observations are comparing at the same exposure, for the shadows you can use more exposure with filmic and offset that aspect of filmic’s dark shadows .

SIgmoid can often be more colorful/saturated out of the gate esp if we are talking v6 filmic…with v5 this is easy to match and control I find. I use the dehaze preset of D&S and it is amazing but the odd time can be a bit too much introducing too much grain/noise but this is less often the case with sigmoid with its softer highlights so its a good match…

We do need to be careful as well with all these comparisons as filmic has choices for the shoulders that impact this quite a bit… I actually use hard for highlight unless they are severe already and safe for the shadows many times… I think the sigmoid look would be more like filmic with both of these set to safe… I think the default in v5 introduced safe as the default and now it is back to hard which is more like older versions of filmic… I think any way…

@nosle Not what I am talking about. Your observation, if true, is easier to deal with than mine.

@priort Sorry, what is D&S? Not a dt user. :space_invader: Dehaze is one strategy but as you note it causes artifacts (and colour shifts).

Diffuse and Sharpen and its called dehaze…to me its just an excellent sharpening preset

EDIT… I do use the haze removal module quite often as well

but I blend in lightness…

Oh, that one, the one which I cannot use due to low resources. :stuck_out_tongue: Yes, an excellent module based on what I know about its algorithm and work put into it.

That certainly helps but still doesn’t solve the problem entirely, messing with colour ratios. The former is a better solution.

Lets face it pixels are pushed all over the place with each module and slider added. For sure efforts should be made to avoid unwanted side effects. If I have a hazy image that needs more contrast or saturation then I will apply the dehaze filter… if it gives a nice pleasing result or a visual improvement I will use it…no way I am going to edit thinking about rgb ratio’s. I know the math is there and I know there are things that can introduce potential issues but even one of the most math anal guys, ie Aurelien says over and over in many video’s… just use your eyes… in the end I am not creating reproduction renders and I am not going out of my way to distort things but I never think twice about rgb ratios when using dehaze. I will use the default, if I like it keep it and if not I try my presets blended in lightness to see if I get the contrast bump with less change in saturation… if neither works I have a varitey of local contrast presets, a couple of tone curve presets in subtract mode and some D&S presets that I will try to hit the sweet spot… In the end for me its a pleasing blend of contrast and color that dictate what I will do and not rgb ratio’s… The good thing is that there are tools to help manage that sort of thing for those that might be or need to be that precise…

Some more image evaluations, this time with module settings. Sigmoid continues to impress. I need to get my color checker out and do some more quantitative comparisons but for now qualitative will have to do. There are times where it feels like I spend an inordinate amount of time bouncing from Filmic to Color Balance RGB to Tone Equalizer on those edits as once I change one setting I have to tweak another, Sigmoid seems simpler in that regard. I’ve also done some comparisons with Filmic v5 and Filmic v6. These are also Nikon NEF files instead of Fuji RAF files like from the post above. I find I like the way Sigmoid handles reds and more gracefully goes to white with blown out backgrounds with less tweaking than Filmic needs.



Filmic v5:


Filmic v6:


Another comparison, this one I think I like the v6 edit the best but none of them are what I’d call bad.



Filmic v5:


Filmic v6:



Thanks for sharing…

I find for me the reason I am using v5 is for the look I can get with no for preservation, some amount of latitude and mid tone sat with v5 as the added control or benefit to using it instead of v6 and of course it doesn’t have the gamut clamping so I think its not surprising at least at first glance that there is not a lot to choose between those in these particular examples since you kept the settings pretty similar for the two…

Is the girl masked… the border between background and her outline is quite different … I was wondering if that was down to the tone mappers or a slight difference in processing or exposure?? You can see it on for example her hair or arm when you toggle through the images…

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Good catch! No masking, just fly away hairs on a blown out background. In Filmic I trimmed in the white exposure point along with some Tone Equalizer to have them disappear. If you bring the skew in Sigmoid over more to the right and tweak Tone Equalizer a bit the ghost effect disappears. Still learning Sigmoid workflow. If I were shipping these out again (these images are several years old) I’d remove those with the GIMP or Krita. What’s funny is they aren’t near as visible in darktable with the RAW just on the resized output JPG. Intentionally blown out backgrounds seem to be a struggle point for a few tone mappers.

Screenshot from 2022-11-19 18-56-39


Could you share the portrait image (or any other intentionally “blown out image”) here or with me? It’s a good case for when the design of converging to white doesn’t perfectly align with the intention of the artist! I would like to do some tests to see if I can make a recommendation for this thread and later the manual.


Now yes: Sunset over Vierwaldstättersee

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Yes here is the RAW. Keep in mind my issues may be newness to Sigmoid and moving too quickly or not reading documentation thoroughly.

I need to dust off my math from my grad school days and get back into this but it’s been a decade or more.

Licensed under CC BY-NC-SA

_LGH0100.NEF (39.2 MB)

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It is a shame that the 2 concepts do not sit under the same ‘hat’. They both have differing strengths and I find myself messing about with each in order to feel comfortable with the end result. … bit of an unfortunate waste of time, I am never really sure which solution is going to best fit the image needs.
Maybe some of filmic’s options should migrate into sigmoid!

Personally, I’m quite happy having two separate options - filmic already had too many options in it, IMO. (not complaining, just thinking aloud!)
I suppose it wouldn’t hurt sigmoid to have slightly more control in some way, thinking highlight gradation especially, but I’m not sure whether that is something that could be incorporated into it’s function in a sensible way.
I’m quite happy anyway :grinning:

BTW, in relation to the discussion further up this thread about highlight ‘clarity’ for want of a better word, I thought the image in the thread: Any way to recover the sky and highlights in this shot? - #15 by 123sg was quite a good example.

I think you can match them most times… filmic just can have a bit more tweaking but then that gives it a few more options… the strength I think of sigmoid is that for many I think a fixed setting will serve as a good basic tone mapper without fiddling and people will finish the image with other modules… In many cases I think AP felt this should be the way to use filmic but because it had extra sliders people feel the need to keep tweaking… When you go through many play raw files its amazing the number of nice edits and people have not even bothered to adjust the white and black points from the defaults… I think speed and simplicity will be the real strength of the sigmoid module and cluttering or complicating it in any way could potentially remove that feature.


@123sg There was a discussion on ways @jandren could approach the module a third of the way in the original thread. At the time, there was much “hesitancy” on sigmoid, so he decided to make it a simple proof-of-concept module. I (and others) cheered him on: here we are now. :slight_smile:

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Thanks for the info Alan. I’m not sure if I read that bit… but in any case I’m really happy with how it turned out. :clap: :tada: I hope my post above didn’t sound critical - it certainly wasn’t my intention :slightly_smiling_face: Well done to all involved!

@Jandren … curious how you would set sigmoid settings for this image… pull back contrast and add as needed by other means??

Hello, thanks for the very nice module, been using it since yesterday and had some nice results with nice lights popping.

I was revisiting this old picture i first developed with filmic, and i noticed that using sigmoid defaults, the sky was very desaturated. Then using “rgb ratio” color processing the blue came back. I don’t know if thats an intended behavior, I’m ok with this, but i also havent easily found an explanation of the difference between “per channel” and “rgb ratio” (on the github merge page there are pages refering to this but it’s more on the technical side). I wanted to understand a bit more directly how to use those two color processing modes, or if its just “experience and trial and error”. But maybe it’ll be in the docs. Sorry if this question has already been adressed or is common knowledge but haven’t found easily information.

(all below are fast simple edits)

Sigmoid, 1.500 / -0.63 / per channel / 100%

Sigmoid, 1.500 / -0.63 / rgb ratio

Simple filmic edit

I’ve had this behavior also (but bit less) on another image where the sky was less blue.

Here is the raw file if its of any use (CC0 copyright)
20220527-0026.nef (22.1 MB)