Clarity in darktable

Yes…!
I think that blend modes could be an interesting topic to investigate and discuss in the forum. Which blend mode to use with which modules in which situations? And which blend modes doesn’t go well with the filmic way of editing photos?

There are many blend modes, but I have only seen the following used in “normal situations”: multiply, screen, softlight and overlay. Blend modes are apparently seldom used in the darktable universe……

1 Like

I use blend modes all the time in a pixel editor (photoshop or affinity - haven’t used gimp yet). Never thought about using blend modes in a raw editor.

can you please explain this with some example pics as to when to use single instance with multiply blend mode and when to use the second instance with normal. specially when to to use which method

I am a bit confused.

:point_up:

Look at the road. Without local contrast there are few details:

Local contrast with multiply blend mode:

Picture is darker, and colors are better, but I want more contrast on the road.
Second instance, just to emphasize details a bit more:

This is simply a matter of taste, no tricks or anything particularly intelligent. :wink:

3 Likes

28 posts were split to a new topic: New Channel Mixer thread… how do you channel mix?

Thank you for the hint.

I have watched the video “fast workflow for pros/time-constrained photographers” as recommended.

2.5 hours of video can seem a little bit scaring if you are time-constrained…:grinning:! But since the video consists of a lot of examples of editing you can stop or pause anytime. I can absolutely recommend the video.

All the editing is being performed with a fixed setting of filmic! No filmic slider is adjusted in 2.5 hours! All the editing is done by using the exposure module (in automatic mode) and the color balance tool (and sometimes a few others: white balance, lowpass filter etc.). @anon41087856 is playing the darktable concert instrument for 2.5 hours, excellent and a lot of tricks to be learned.

I’m left with one question: in which situations should you adjust the filmic settings?

1 Like

When you want to tune your virtual film emulsion, especially for the balance between highlights and shadows.

Hi’ @anon41087856

I asked: I’m left with one question: in which situations should you adjust the filmic settings?

and your answer is:

……and this is not often required? If yes, I suggest that the user manual is modified so you up front are advised to turn on filmic using your settings and not touch it again unless you have special needs.

As of now, you have to read through page 108-114 and try to digest the information. In the end, you get a suggested simple workflow, but more complicated than the one presented in your video.

By the way: you can assign a shortcut to your excellent preset by presets>shortcuts>global>styles and then click on the style you want to assign a shortcut to…….:grinning:

Thank you for an excellent video and a fine preset, works really well……

1 Like

I am but a designer. Meaning I try to solve people’s problems.

Some people (like me) want a fine-grained control. They can tweak filmic ad nauseam, following the manual.

Some people want a semi-automatic way to process images. So they can use a preset, leave filmic as set, and bother about exposure.

Nothing is ever required. It’s all about matching intent and method.

AH, I knew it was possible somewhere :slight_smile: Thanks !

Yes, the channel mixer is a simple tool, at the foundation of image processing. It does exactly what the input color profile does : a matrix multiplication. As most simple operations, it is very powerful in terms of use. And yet, simple operation doesn’t mean simple to use. I don’t think you can escape some theory if you want to use it.

4 Likes

Disclaimer, before I start: I’ve messed with the dt filmic module just enough to know I need to go and watch @anon41087856’s videos… so, I do not have specific knowledge about how they work.

But, I do know the fundamental characteristics of a filmic curve, and to me that’s important to developing heuristics regarding its use. Essentially, it’s log-like, with a toe on the left end. You play with the toe to “crisp-up” the blacks, and you play with the shoulder and central linear line to mess with the overall tone distribution. In rawproc, my tone tool has a curve plot to show one what the selected tone operator and its parameters will do to the image, and I’ve found that to be of critical importance in applying it to particular images.

For instance, my test raw for rawproc is a scene with a specular highlight (locomotive headlamp), a mid-morning cumulus-cloudy sky mixed with locomotive steam and smoke, and a triple-headed train where the locomotives sport various shades of gray-to-black. When I scale the image to fit black-white where the headlight is blown (don’t yell at me @heckflosse, I’ll get around to figuring out librtprocess highlight recovery… :smiley:), it almost looks good as-is, linear. Indeed, when I put the basic filmic on it, the steam, smoke, and cloud definition gets lost in that rather lofty shoulder headed to white. Really, I’ve found that the best curve for this image is a custom curve with two control points: one on the exact center of the line, unmoved, and a lower one drug slightly below the neutral line to pull the shadows down a bit.

So, summed up, here’s what I think is important about any tone curve selection:

  1. know what linear looks like for the particular image, and,
  2. know the transform curve of whatever tone operator you apply to move from linear.

That’s it. log, log-gamma, reinhart, filmic, custom; same two fundamentals.

In the snowstorms around here, I had a few pictures outside the house. This is the first time I was missing some of Lightroom’s highlight controls :).

The problem was not getting the highlights within range or anything, filmic did it nicely. But to make the snow pop a bit more you need local contrast or something.

Local-contrast module didn’t seem to do it, or at least not enough from what I was searching for.

I ended up (after the normal white-balance, exposure, color calibration, filmic set) adding local-contrast, but in the bilateral mode. Turn the contrast all the way down, put the details quite high (too high for comfort) and adjust the coarseness this way till you think it right.

Then I add a parametric mask, enable the ‘mask-view’ mode and turn the L of the parametric section up till you only have the highlights selected. This way it only works on the highlights (snow) without affecting the rest of the image. Put the feather-radius and mask-blur up a bit so the mask has no sudden edges.

If the effect is too strong, turn the opacity of the mask down to control it in a smoother fashion.

With the contrast down I get no haloing whatsoever. At least not on the few pictures I took yesterday :).

1 Like

Yep, most tone curves are flat at the top, so high-key things like snow tend to suffer in contrast. The challenge is to make the tone curve slope at that point steeper, without goofing up adjacent areas’ contrast… That’s why I’m reverting to a control-point curve in some instances; no math to get in the way of that. :laughing:

@jorismak Try some dramatic shift in the contrast fulcrum in CB and play with contrast…sometimes you can hit it right and you can drive it in just the right place. Also subtract blend mode at a very low opacity say 5-15 % can have almost like a dehazing effect…I have not tried it on snow but on light outdoor pictures around water it bring a nice effect. I have gone as high as 25% but rarely and after that it will just get dark… I often apply it with just a strait tone curve or maybe a small tweak to the curve…

I set up a parametric mask as you describe and then apply a tone curve, pulling it down to increase contrast in the highlights. It works pretty well as long as I’m not too aggressive with it.

Actually, increasing the local contrast in new darktable is very simple. You have to make use of the blend modes. Especially good for this is multiply reverse blend mode.

Here is an example. This is the scene I just photographed from my window:

After white balance and exposure compensation it looks like this:

Actually already very nice, but the details in the snow are missing. These areas look very flat.

In filmic I compress the shadows and highlights a bit more to have more room in highlights. Since this reduces contrast, I reduce latitude and increase contrast in the “look” tab. This is what the photo looks like afterwards:

Now the photo is ready to increase the local contrast. For this I will use local contrast module with multiply reverse blend mode. First I choose the RGB (scene) option in the blending options tab:

LC4

Then I take multiply reverse as blend mode and in the module itself play with the sliders detail and midtone range and in blending options with blend fulcrum and opacity. This is how the result looks like:

The advantage of using these blend mode is that the increase of the local contrast is accompanied by a matching increase of the contrast itself - in that multiply reverse blend mode darkens the highlights to the extent that they are shifted in the direction of the midgray - which looks much more pleasant than the increase of the local contrast alone. This comes pretty close to what some call “clarity”.

If this makes the photo too dark, you can increase the blend fulcrum, which will overexpose the highlights…

…but you can get them back quickly with the help of tone equalizer:

Difference before - after is quite clear:

16 Likes

Thanks for this tip.
Two questions:

  1. do you move the local contrast module before filmic in order to work with linear rgb unbounded data?
  2. any way to reduce the color cast on the snow in the final image?

No. This is not necessary. Everything that comes before the filmic serves for me rather as preparation (the basis) for the perceptive adjustment that comes afterwards. This way I make sure that I have enough space to shape the photo the way I want it to be. Local contrast is part of this perceptual adjustment for me that comes after filmic.

In this case however - although the processing takes place in the perceptual stage - I have “misused” the blend mode that belong to the linear part of the processing, simply because it gives nice results.

There are a lot of ways you can do this in the darktable.

Interestingly, in this particular example, there are no color shifts. The scene was indeed like this. The front part of the trees and the deck chairs are illuminated by the reflection of the sunlight from the orange house wall in front of them and the snow in shadow area is illuminated by the blue sky.
It is this play of colors that makes the scene so interesting to me!

But to answer your question, here I can use two instances of the color calibration module for this - one for blue snow in shadow (with appropriate parametric mask) and one for orange snow (of course also with appropriate mask):

You can also use various other modules for this - color balance, color zone, color look up table and so on.

The simplest version would be to mask the snow and desaturate it, since it has no color itself.

3 Likes

Very good explanation.
I would like to comment that maybe you need to readjust "filmic or “tone equalizer” after local_contrast. I usually check that I didn’t burn some areas when I apply it.

I always try to arrive to filmic with low contrast in the scene (some margin in black and whites) and a bit lighter in the middle tones, because with local_contrast and multiply_reverse blending mode I darken a little bit the picture.

Yes, I sometimes even correct the exposure afterwards. That’s the nice thing about pixelpipe, that you can still adjust the values in modules nicely afterwards.

1 Like