It is my understand that light room is full of said pet tricks and “magic.”
prioritize ... *over* .... 
or, dare I say,
options and capabilities *are* simplicity and ease of use. 
Clutter to you is treasure to me. — @afre 
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Hallo afre,
thanks for the quick answer. But I still don’t quite understand when and why the black level control is used. I liked to use it to increase the depth of an image so that the black doesn’t just appear dark grey. Probably that was wrong. My question: When and why do you use this control Black?
micha
It wasn’t a complaint. It was just an observation. I appreciate all that you do.
I’ve used it in the past to crush shadows to make a lighter foreground stand out. I use a curve to do this sort of thing now, keeps some definition in the lowered shadows.
Hi!
You would check this discussion for the “get curves plugin”
https://discuss.pixls.us/t/get-the-curves-difference-between-2-images-like-get-curves-plugin-does/7626
This curve is the equivalent of +50 brightness slider in rawtherapee
This curve is the equivalent of -16384 black level (for some reason the saturation here doesn’t match)
This curve is the equivalent of a +1 EV exposure (check that button to apply the curve in linear gamma)
??? The black level is an offset, how could it be a curve ?
I recommend finding a low-contrast picture and load it with the Neutral profile. Then, play with slders and see the effect on the histogram. My conclusions are:
- “Exposure” simply shifts the entire histogram without modifying its shape, unless it clips.
- “Black” moves the darkest point without modifying the brightest point. The histogram gets stretched (which implies increased contrast).
- “Lightness” shifts the histogram like “exposure”, except that it doesn’t let it clip, and it gets “bunched up” (reduces contrast) when you are near the boundaries.
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I seldom adjust black levels. In most cases, raw processors set them at reasonable levels. If not, consider submitting a bug report for your particular camera. Read more about black level here.
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Hello,
I have only changed the black value so far because it was recommended in Exposure - RawPedia. = “Black Use this to set the black point. See the left side …”
You mean, you don’t have to adjust this value at all?
micha
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Ah, thanks for clarifying. This is a different black setting, related to tone compression. I was talking about raw black levels since that is what one usually refers to as black levels.
Hello,
sorry, the misunderstanding comes from the translations. I mean the slider in Exposure → Black.
When does it make sense to adjust this slider: Black?
micha
Here’s an example of an image where I crushed the shadows to 0,0,0 by setting a black point:
(I think I’ve posted this previously, but can’t find it)
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@micha Learn by doing. That is what I do anyway. There are plenty of #processing:playraw files for you to test this on. Try using it with Shadow compression.
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Hello,
I thank you for all the hints that help me better understand RT. I also practice this learning by doing and I am progressing slowly.
Nevertheless, I would like to understand what the Exposure - Black control really does and when it makes sense to use it. Is there a clear answer?
micha
There are seldom clear answers, since raw development has an artistic component and there are several ways to achieve a particular result.
Having said that, and to complement what I said above: If you want to set the “blackness” (or “grayness”) of the darkest point in the image, but you want to leave the bright parts alone, and don’t mind an increase in contrast: use the Black slider.
I don’t use it very much, because I find it hard to control how much contrast is added. I prefer to add contrast using curves, because then I am more in control of the result.
Clarity can be found in the math behind it. All of these operations that affect the tone of an image are what most know as “transfer functions”, where for every input (say, X), there’s a distinct output (say, Y). “Black” is sometimes called “setting the black point”, where all values below the setpoint are just made to be zero, and positive tone values don’t start until > blacksetpoint. After the setpoint, the tones are transferred with a slope function between the black setpoint and white, so the complete function is:
Y = max( (X - setpoint) * slope), 0)
If you’re familiar with curve tools, doing a blackpoint in that might make more intuitive sense. To do so, open or apply a curve, then drag the bottom-left point, the one at 0,0, to the right along the bottom. The X where you drag it to is the blacksetpoint. Any value below that just becomes 0, any value above that is translated per the straight line that slopes up from the setpoint to the top-right. I’d post a screenshot of one, but I’m not where I can make one right now…
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Hallo Glenn Butcher,
Yes, it would be nice to see such a screenshot. I’m looking forward to it. Thanks in advance
micha
hello mbs,
thank you very much. Sorry it took me so long to understand. Also translating into my language (German) with DeepL does not always promote my understanding immediately. May I summarize briefly: So the control black is not really useful and also not necessary, it is better to work with the curves. I like to use the parametric curves in Lab mode. Is that ok?
I really like hearing that the raw development also has an artistic component, so it doesn’t work according to just one strict rule.
Thank you for your help.
micha
I recently used the black slider to ‘crush’ some blacks in black and white images where I was going for a harder tone. Although in this case I happened to starting from jpegs and not raws. Here is the series (sorry I can’t remember which ones required use of the black slider).
https://www.dpreview.com/forums/thread/4398963