Extreme light-dark differences - ART vs RawTherapee [solved]

In which order does it make sense to use the tools?
I assume

  1. Dynamic Range Compression
  2. Exposure
  3. Tone Equalizer and Tone Curves.

How did you do it, Alberto @agriggio ?

And, of course, it would also be interesting to see how you would have developed the picture to your taste.

The order is not relevant, it’s according to personal preference. I usually start from a preset with a default tone curve that I rarely touch, and use other tools to manage the dynamic range. But YMMV really…

Wonderful: I have now understood a lot.
Now I’ve done my own development, not with dynamic range compression but with log tone mapping, and I’ve come to roughly the same result as Alberto.
Even with just the Tone Equalizer and the Tone Curves I get very far.

So far I haven’t had a good setting in the tool: Local Contrast, if I use your setting curve,
then this image will be about as crisp as I had made it with RT.


Also, the order is really not important.
Now I see that it is not witchcraft to make good developments, but the masterpiece is obviously ART itself.

Hello sguyader,
Your tip is not quite as convenient as I had hoped - but very helpful. After all, you only have what you have earned yourself.

Alberto’s wiki on bitbucket are a great, but not so easy to understand if I’m missing too many basics.

My question about Log Tone Mapping:
When to use this tool? Only to compensate for high contrasts? Or does it also make sense for normal photos?

ART Reference Manual says: Gain (Ev) - Amount of exposure compensation to apply before the tone mapping. Do you know what this means?

These 6 sliders cause the image to become lighter or darker. Hence my question: Where to start?

Or, so that you don’t have to rewrite everything: Is there a comprehensible manual for this?

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I watched exactly this video this afternoon. You mentioned it. I listened to everything. It didn’t improve my understanding of the tool.
Of course, the language barrier plays a big part in this. The translation into English is very poor in places because the Frenchman speaks very quickly. Also, my English is not good enough to understand everything.

It would help me a lot if I knew when to use this “log tone mapping”. Is it only there to raise the shadows and lower the highlights, as Alberto describes in the manual?

Is this tool only used when the contrasts are too high to soften them?

I think the best way to do this is through diligent and systematic trial and error.

Hence my question: Which slider is used to start the correction? And which one is then used to make adjustments?

It can depend on what you want to do with the image… for sure its a tool to manage dnr… but just as a parallel example the default workflows in DT use either the sigmoid or filmic tone mapper. I don’t like them applied before I see the image and I often don’t use them. If I don’t need to manage DNR in a way that they are necessary I get by with the tone eq (DT version) and a few other modules as when you use one of these tools to compress tonality you can kill a lot of the details… sigmoid in DT does a wonderful job on midtones and color but decimates the details in the highlights so if your image has those important details you have to add it back… so why kill it and then fix it or restore it if you dont’ need to … other times there is no option. Without some tone mapping the image DNR is a problem… So long story short I would use it when you feel your image needs tone mapping and if not I suspect the standard curve in ART plus tone eq (ART) tweak will be all you need… Others might have totally different ways to attack things… there is no massive right or wrong here as far as I am concerned… if you craft the desired look with a tool then use it when and where you see fit…

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If you want a recipe, for most images you can get by with just the brightness slider (the top one), and you can leave everything else at its default value.

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If you mean a single, start to finish complete “book” on ART the answer is – as far as I’ve found – unfortunately no. That was part of my motivation in trying to compile the ART Reference.*

There are resources, although it’ll take a bit of time and effort to put it all together in your mind. I’m definitely still working on it.

  • Read all the documents / articles linked on the ART wiki.

  • Search the ART forum for posts from Alberto. He quite often includes in his posts little nuggets of explanation on specific features. The forum isn’t so large that it’s impossible to “read it all” given a little time.

  • Read RawPedia (which I assume you have :slight_smile:). But in my case I found that fairly often some detail in RawPedia helped my understanding of ART, even when the corresponding ART feature was a bit different.

* For the record, although I put the ART Reference together I didn’t “write” it as such. More accurately I compiled and collected it from other sources as much as possible. I wrote little tidbits here and there but tried to make my “contributions” mostly state the obvious.


Hello priort, what you say helps me a lot.

The nice thing about the Tone Equalizer is that the sliders do exactly what you expect them to do. The same applies to the curves, of course. I am very familiar with this and have no stress.

As I understand you, I only have to worry about Log Tone Mapping when the contrasts are difficult to control. That reassures me a lot.

you can kill a lot of the details

That is a very important hint for me. I have now been able to observe it myself.
I have now achieved at least as good a dynamic balance with the Tone Equalizer, but with full definition and detail in the highlights - in other words, a much better result.
This makes me very happy, because I have loved ART from the very beginning, because of the Tone Equalizer, which is so excellent and self-explanatory.
I don’t want to say anything negative about the Log Tone Mapping, just this much: you don’t necessarily have to use it all the time.
Thank you all for your help.

Hello Iphilpot,
Of course I know your ART Reference Manual - it is very valuable for getting to know ART.
You’ve also briefly described Log Tone Mapping there with lots of technical terms.
As soon as I understand that you only use this tool when the contrasts are difficult to control, I’m at peace. My mistake was that I thought it was a miracle tool that should always be used successfully.

Can you describe the difference between Target gray point and Gain? They make very similar changes in brightness.

Honestly I can’t. Alberto provided that part. :slight_smile:

I think but I stand corrected that using gain is like the EV boost you give to filmic. It is something that is being applied to the image before the tone mapping and I think the target gray is part of the tone mapping and sets the desired target value you want to map to. Still nuance and likely not helpful but I think similar to filmic in DT with exposure and middle gray sliders… perhaps the rationale is similar as well… and I forget the nuance to why its preferable to use exposure in DT… I think it has to do with the way the modules interact with filmic around the middle gray value and so it is better to set it with exposure and not to add some value dramatically different than 18% in middle gray… this may not be the case at all in ART esp given that @agriggio above suggest to move a different slider than the gain slider in a generic application of the module… so maybe I am wrong…

My investigations revealed:
Target gray point (brightness)
Reduce: the brightness, but not the clipping.
Increase: Brightens the shadows in particular, increases clipping only minimally.
Presumably affects the midtones and shadows in particular.

Gain (Ev):
Reduces the brightness and clipping.
Increases the brightness and clipping.
Probably affects all tonal values evenly.
Behaves very similarly to Exposure compensation.

This is where my comments came from…