Following some discussion with [Todd Prior] about an image I posted earlier (on Facebook) I decided to have another look at the Tone Equaliser to further understand why I dislike this module. I have watched Youtube videos by Bruce Williams and Rico Richardson and read the relevant pages in the official manual. Furthermore, I have read Ansel Adam’s book about the zone system. so I have a broad understanding of the zone system. The problem that I repeatedly encounter when trying to use this module is the ‘global’ adjustments it makes to an image. To give a specific and repeated (in my experience) example: I have an image with a nice sky with lots of texture and detail. The remainder of the image is contrasty and lacks detail so an ideal candidate for the TE module you would think. In my hands the module does improve the image but inevitably (it seems) destroys the sky. It ends up bland and losing detail and texture. ‘No problem’ I think, ‘I will create a mask to isolate the sky from the module’.
I guess that as the crux of this module is that it works by creating a mask of the image to delineate the luminosity zones across the image of greater or lesser granularity and then to assign these zones to adjustable yet interconnected points on a tone curve, there is some quite valid technical reason why it appears (to me) to be impossible to divide the image using a drawn mask so that the sky is isolated from the effects of the module.
So frustrated by this limitation, I have two options: Create two edits of the image to treat the sky differently than the remainder of the image and then blend them in (say) Gimp. Or don’t use the TE module and use several instances of the exposure module with masks to more precisely dodge and burn the various areas of the image. Whilst apparently more labour intensive than the TE module, I get more consistent and repeatable results from the latter method.
Probably, I have misunderstood some fundamental step in adjusting the exposure or contrast compensation even though I am aware of the orange clipping zones. In any case, I occasionally use the module with the simple tone curve preset. That itself is interesting because after selecting this preset and inspecting masking tab it sometimes shows a clipped mask.
I have added the TE module to my customised collection of favourite modules but I return to it less and less so I am resigned to removing it.
As a footnote, in all the videos I have watched where this module has been used, the result has always be underwhelming so although I am thankful for the many great aspects of darktable and now use it almost exclusively for editing my images, the TE module is (IMO) the least useful, intuitive or impressive.
Just a thought, have you tried decreasing both the smoothing diameter and the edge refinement in the masking tab? I have found this can bring back some local contrast but can risk more halos so it is a balance.
Also tweaking the exposure and contrast so that your zones end up covering the tonal values that you want can have a big effect.
Also try to avoid large slopes downwards in regions of lightness where you want there to be contrast.
Perhaps you know all these already, and I am not addressing your problems but doing these things helps me…
Thanks for your suggestions. I have tried many things but end up with artifacts, halos etc so I always end up reverting to exposure module instances.
Please post some problematic images and annotate what you want to do with TE and also post the masking settings from the module.
I would say that @s7habo has the best and most comprehensive series on the tone eq. He even has at least on or two videos where he specifically addresses the preservation of details… If you have not seen these I think it is the best information out there in video on the tone eq…
Share a couple of edits Berny…perhaps ones you struggled with and see what tips you get…playing with the mask filtering and quant can also give a very different result…it can be a matter of stumbling on it until you get something to work…Initially I used one tone eq module and spread the mask evenly …now if I use it I know I will use 2 3 or even 4 and not try to do too much in one…and I often shift the mask and don’t care about clipping on the end I am not trying to control in that instance…
I have watched many of Boris’s videos and I have seen at least one where he used a drawn mask with the TE module but I can not emulate it when I try. My mask just does not seem to isolate any part of the image.
That’s an interesting approach. I had not thought of using several instances. Maybe because I assumed each new instance would negate previous instances.
And you can move them in the pipeline to preserve what you have done or move other modules…but really using multiple instances and only targeting a small aspect at a time works much better IMO…also using one mode to lighten and one to darken…ie preserve details vs not to…
Episodes 54 and 57 are pretty good for TE info…
I spent some time last night trying a few different things with the TE module and eventually managed to get it to work in combination with a drawn and parametric mask so that should help. However, I did find that the mask often spontaneously switches off and the whole image is then adjusted. This happened when I created a mask then switched to a preset. I had to recreate the drawn & parametric mask. The drawn mask had been stored in mask manager but had lost feathering setting and detail threshold. Now that I’m aware of this, I keep an eye on the mask section and make a note of these values so that I can easily restore them. Incidentally, I have noticed the same behaviour in the diffuse or sharpen module.
Programs don’t have free will
Yes, mask settings are part of the preset. Very useful in some situations (e.g. pulling down highlights with exposure module).
If you often want to apply or change presets with a mask already created, you can use a copy of the exposure module, create your mask there, and use the “raster mask” function to reuse that mask in other modules later in the pipeline.
The exposure module is a nice one for this, as it’s fairly early in the pipeline, and has a neutral setting, so won’t change the image (it will server only to define the mask). It even works with several masks : you can select which earlier module provides the raster mask, provided that that module is active.
#rvieto That’s a very good ‘hack’ which I have used myself but had forgotten about. Thanks for the reminder.