June 23, 2018, 04:42:23 AM

Author Topic: Setting black and white points. Very divergent results.  (Read 1002 times)

llre

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Setting black and white points. Very divergent results.
« on: May 21, 2018, 05:00:41 PM »
Starting from zero...

First, I used the "ALT" method. I ended up with +33 white and -12 black.
Next, I tried "auto". I got +33 white and +38 black.
Why the large difference with blacks? Is this my problem: my images are of 19th century documents on a black background. The camera  and/or ACR are being "tricked" somehow?
Just wondering about this.
thanks
Robert

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Setting black and white points. Very divergent results.
« on: May 21, 2018, 05:00:41 PM »

LDS

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Re: Setting black and white points. Very divergent results.
« Reply #1 on: May 24, 2018, 04:18:55 AM »
What version of ACR? The "Auto" mode is know for not being effective in many situations, it is probably based on average images - in Lightroom the latest versions can use machine learning - often called AI - to individuate better settings, but I don't know if it's available in ACR. "Auto" will also change other settings.

Your situation I guess needs manual settings - you need to decide how "black" the background should look - you know what material it is and how it was lighted, albeit with proper lightning, if possible, later adjustments could be limited.

Mikehit

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Re: Setting black and white points. Very divergent results.
« Reply #2 on: May 24, 2018, 05:18:20 AM »
With an image like I am envisaging, I would expect the 'Auto' to be adjusting pretty much everything - exposure, shadows, blacks etc - with the intention of bringing detail into the shadows (which you may not want) and once you raise shadows, dropping the black point will re-introduce lost contrast.

stevelee

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Re: Setting black and white points. Very divergent results.
« Reply #3 on: May 24, 2018, 10:57:33 AM »
In my experience, ACR’s auto exposure setting usually ramps up the white and almost maxes out the highlight recovery (slider to the left) and often just about maxes the shadows exposure. The results can look natural, or more often downright cartoonish. I try it sometimes as an aid to deciding what I want to do. It is easy enough to go back to Default.

For black and whit adjustments I mostly go by the histogram. I usually have the box clicked on the black side and occasionally on the white. If color is way off, I will usually do the temperature and hue setting first and will probably come back to adjust after exposure settings change the look.

I will start with tweaks of the exposure and contrast if either looks obviously off. Then I do the back and white sliders and almost always recover some highlights and boost shadows a bit. But shadows can do more to brighten insignificant details to the distraction from the subject, so I’m careful about that.

For me, the most “objective” white and black point settings come from the auto in Photoshop’s Levels command.

LDS

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Re: Setting black and white points. Very divergent results.
« Reply #4 on: May 24, 2018, 04:02:25 PM »
For me, the most “objective” white and black point settings come from the auto in Photoshop’s Levels command.

ACR/LR basic panel sliders work in a more complex way than Photoshop Levels, and they are often interrelated (BTW, the "white point" depends on the white balance as well) and may not be fully intuitive.

For example, according to Marting Evening ("Lightroom 5 Book: The Complete Guide for Photographers"), "With Process 2012, the Blacks range is adaptive, and auto-calculated based on image content". Evening also says the Blacks and Whites sliders should be used to fine-tune the image after setting Exposure/Contrast/Highlights/Shadows - they are not really the equivalent of Photoshop Levels.

stevelee

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Re: Setting black and white points. Very divergent results.
« Reply #5 on: May 24, 2018, 05:15:38 PM »
For me, the most “objective” white and black point settings come from the auto in Photoshop’s Levels command.

ACR/LR basic panel sliders work in a more complex way than Photoshop Levels, and they are often interrelated (BTW, the "white point" depends on the white balance as well) and may not be fully intuitive.

For example, according to Marting Evening ("Lightroom 5 Book: The Complete Guide for Photographers"), "With Process 2012, the Blacks range is adaptive, and auto-calculated based on image content". Evening also says the Blacks and Whites sliders should be used to fine-tune the image after setting Exposure/Contrast/Highlights/Shadows - they are not really the equivalent of Photoshop Levels.

Yes, that was sort of the implication of my final comment. These complex relationships are both blessings and curses in ACR/LR. I will usually set the exposure-related sliders before I do the white balance, and then maybe go back and forth a couple of times as they alter each other. If the color balance is too weird, though, I'll start there to save many iterations between them from starting with exposure. A bit of Clarity helps a lot of pictures. That can interact with several of the other settings. Sometimes I start with it and then readjust after everything else is done.

I've found Evening's books very helpful over the years (after I get over remembering the old Sam and Janet knock-knock joke). The Highlights adjustment always needs more work after you move Whites. I've read that the best way to approach these sliders is from the top down. But that might relate more to earlier versions of the controls (when they had different names).

LDS

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Re: Setting black and white points. Very divergent results.
« Reply #6 on: May 28, 2018, 05:56:01 AM »
I've found Evening's books very helpful over the years (after I get over remembering the old Sam and Janet knock-knock joke). The Highlights adjustment always needs more work after you move Whites. I've read that the best way to approach these sliders is from the top down. But that might relate more to earlier versions of the controls (when they had different names).

Evening's books often explain what's behind each slider. That's important because the way many slider work may be quite subtle, i.e. they may change algorithm past a given threshold, or add new behaviours. Programmers made a lot of work to "simplify" some tasks that in PS would require several steps using different tools.

IMHO ACR/LR lacks a good help system, and Adobe often doesn't explain well enough how LR works. Sometimes you can just experiment, but sometimes knowing what's happening behind the slider helps to achieve what you're looking for.

The suggested workflow is still using the sliders top-to-bottom because of their interactions, but it's just "suggested" - if you know what you're doing, you can use a different approach that suits best your images and your style.

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Re: Setting black and white points. Very divergent results.
« Reply #6 on: May 28, 2018, 05:56:01 AM »

stevelee

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Re: Setting black and white points. Very divergent results.
« Reply #7 on: May 28, 2018, 11:10:49 AM »
"Don't look at the man behind the curtain," Adobe seems to imply.

The late Bruce Fraser and Jeff Schewe had some really helpful books that dealt with the old version of the sliders. Fraser's work lies behind some of Adobe's algorithms, I gather. Schewe has more recent books that I find useful, if no longer a revelation.

I felt like I had more of a grasp of the old controls. The newer ones are more magical, in good and bad senses of that. So, yes, I feel more like I know what I am doing with Levels in Photoshop, for example, than with the more sophisticated ACR sliders. That doesn't mean the latter are less useful; often quite the contrary.

It probably fits Adobe's business model to have whole cottage industries rise up to help us with their software, whether they planned this or stumbled into it.

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Re: Setting black and white points. Very divergent results.
« Reply #7 on: May 28, 2018, 11:10:49 AM »