Setting black point rather than black clipping

[wsolum]

I'm finding that I can't completely optimize my images in LR.  I have to go to PS in order to truly set the black point.  In Lightroom you can push the clipping point up but it's not the same as finding a point in an image that should be black and adjusting the R, G, B black points independently in order to get colors to snap into place.

I figure the only way to truly do it is with the calibration section, and I've got several calibrations I've done using a macbeth card but they don't work on every image.

Is there a way to adjust the black point channels?  Does anyone else have a problem with this?

Wayne

[sergio]

You have curves in LR which is are precise to use. I use the shadow slider with the black clipping indicator on and then I readjust the shadow level with the small slider on the curve itself. What can be an issue is that the default level of 5 of BLACKS in the BASIC panel is too high. Simply bring it to 0 or 1 and then readjust your black point as indicated above. It works for me. The only tricky part for me was that the densitometer readout values in LR are presented in % and after years of using level values in PS (0-255) it can take some time to adjust.

[wsolum]

You have curves in LR which is are precise to use. I use the shadow slider with the black clipping indicator on and then I readjust the shadow level with the small slider on the curve itself. What can be an issue is that the default level of 5 of BLACKS in the BASIC panel is too high. Simply bring it to 0 or 1 and then readjust your black point as indicated above. It works for me. The only tricky part for me was that the densitometer readout values in LR are presented in % and after years of using level values in PS (0-255) it can take some time to adjust.
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No, this is not the same thing.  When adjusting those sliders you are not altering the relationship between RGB channels at the left end of the histogram and balancing them to black, you are merely clipping the channels in their current relationship to each other.

I'm speaking of something similar to the WB dropper which takes your click point and adjusts the RGB channels so they meet at that point (all three values equal).  This doesn't neutralize the RGB relationship at the left and right ends of the histogram, just at the tonal point you chose.

What I'm doing is making an image look as best as I can in LR using calibration settings and tonal adjustments.  It looks good but there's still a slight cast in the shadows (usually red).  If I want to perfect the image, I have to take it into PS, open levels, find where the shadows start to clip and then move the RGB channel sliders separately to get the clipped area to be true black (or closer depending on the image).  This gives the image the final POP that it needs.

[digitaldog]

Is there a way to adjust the black point channels?  Does anyone else have a problem with this?

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There are not black channels until you render the image.

There's really no reason to want to clip RGB to black when you've got White Balance (where half of all the data lies anyway). Plus if you "clip" black to R=G=B, you might likely hose the color balance neutrality elsewhere. On a 12 bit capture, best case you're dealing with 64 levels in that last stop in a linear encoded color space (6-stops capture).

[wsolum]

There are not black channels until you render the image.

There's really no reason to want to clip RGB to black when you've got White Balance (where half of all the data lies anyway). Plus if you "clip" black to R=G=B, you might likely hose the color balance neutrality elsewhere. On a 12 bit capture, best case you're dealing with 64 levels in that last stop in a linear encoded color space (6-stops capture).
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Okay, my wording may be wrong.  I don't want to adjust the "black channel"  (CMYK?) but fix the mudiness in the shadows by balancing rgb at the low end -- I'm talking a tweak of 2% or less in one or two channels.  But nevertheless, I gather there's no way outside of the calibration settings or using PS to correct this.

The problem arises when I don't shoot a gray card or change light or camera position without re-shooting one.  That's when I have to guess at WB and I invariably screw it up.

[timhurst]

Okay, my wording may be wrong.  I don't want to adjust the "black channel"  (CMYK?) but fix the mudiness in the shadows by balancing rgb at the low end -- I'm talking a tweak of 2% or less in one or two channels.  But nevertheless, I gather there's no way outside of the calibration settings or using PS to correct this.

The problem arises when I don't shoot a gray card or change light or camera position without re-shooting one.  That's when I have to guess at WB and I invariably screw it up.
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[digitaldog]

Okay, my wording may be wrong.  I don't want to adjust the "black channel"  (CMYK?) but fix the mudiness in the shadows by balancing rgb at the low end -- I'm talking a tweak of 2% or less in one or two channels.  But nevertheless, I gather there's no way outside of the calibration settings or using PS to correct this.

The problem arises when I don't shoot a gray card or change light or camera position without re-shooting one.  That's when I have to guess at WB and I invariably screw it up.
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No, I understand the point and wasn't referring to CMYK in any way.

IF you're shooting Raw, toss the gray card and get a white card (or better, the Macbeth color checker) so you can WB on the 2nd white. Again, you're dealing with linear encoded data. Half of ALL the data you're working with is in the first stop of highlight. If your goal is to do what we'd normally do in a gamma corrected image (gray balance using a gray card, let alone mess with the black pixel clipping), use WB. But this is different from black clipping where you decide where 0/0/0 should be from what was previously a higher value (1/3/2). Note too, all the noise is down there and if you're not careful, you'll be working with levels that don't accurately represent black. Clipping correctly helps in noise removal (assuming you don't mind clipping some possible tonal data you had hopped to see).

[eleanorbrown]

I'm finding this discussion very interesting as it is something that I don't entirely understand---re: white balance and black point along with white point too.  I have wondered if I should adjust the individual RGB sliders individually so they stop just before clipping at both white and black points??.  however this seems to change the whole color tone of the image (for instance when shooting at twilight when the light is very blue (should I leave the highlight sliders "as is" or individually adjust so it changes the color of the light in the highlights.  I may not be making any sense here because this is something I don't entirely "get".  I work in lightroom with phase one files so I have lots of bits to work with.  Is there any source on the internet that will explain all this in minute detail?  Thanks! Eleanor

No, I understand the point and wasn't referring to CMYK in any way.

IF you're shooting Raw, toss the gray card and get a white card (or better, the Macbeth color checker) so you can WB on the 2nd white. Again, you're dealing with linear encoded data. Half of ALL the data you're working with is in the first stop of highlight. If your goal is to do what we'd normally do in a gamma corrected image (gray balance using a gray card, let alone mess with the black pixel clipping), use WB. But this is different from black clipping where you decide where 0/0/0 should be from what was previously a higher value (1/3/2). Note too, all the noise is down there and if you're not careful, you'll be working with levels that don't accurately represent black. Clipping correctly helps in noise removal (assuming you don't mind clipping some possible tonal data you had hopped to see).
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[digitaldog]

I'm finding this discussion very interesting as it is something that I don't entirely understand---re: white balance and black point along with white point too.  I have wondered if I should adjust the individual RGB sliders individually so they stop just before clipping at both white and black points??. 

Individually? No.

Clipping highlight and shadow is real simple in both LR, CR and Photoshop visually using the clipping overlay. For example, open an image in Photoshop, invoke Levels and move either black or white sliders while holding down the alt/option key. You'll see when individual color channels clip (they appear as colored pixels) OR all three channels clip (they appear pure black or white). We have this in Curves, and in tonal corrections in LR and CR using the same modifier keys. Its every easy to clip anywhere you wish by viewing the overlay.

[eleanorbrown]

I do this in Photoshop in curves, but when i start clipping I eliminate shadow detail so I usually stop the black slider just before clipping or maybe just clipping the first color to clip, just a little bit (with minimal clipping).  Is this what you are talking about?  If I start clipping to black in the clipping warning, my image looks dark and very very harsh usually.

So is what you're saying I should do all my color balancing using the WB tool and not bother altering the color balance by individually moving the black and white point sliders?  I also use a white card in the field for color balancing if I remember to bring it with me.   eleanor

Individually? No.

Clipping highlight and shadow is real simple in both LR, CR and Photoshop visually using the clipping overlay. For example, open an image in Photoshop, invoke Levels and move either black or white sliders while holding down the alt/option key. You'll see when individual color channels clip (they appear as colored pixels) OR all three channels clip (they appear pure black or white). We have this in Curves, and in tonal corrections in LR and CR using the same modifier keys. Its every easy to clip anywhere you wish by viewing the overlay.
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[digitaldog]

So is what you're saying I should do all my color balancing using the WB tool and not bother altering the color balance by individually moving the black and white point sliders?
[a href=\"index.php?act=findpost&pid=169750\"][{POST_SNAPBACK}][/a]

Generally speaking yes. But the bottom line is, producing a desired color appearance. I often set WB in Lightroom, then tweak temp or tint to taste.

[ariaaudio]

... For example, open an image in Photoshop, invoke Levels and move either black or white sliders while holding down the alt/option key. You'll see when individual color channels clip (they appear as colored pixels) OR all three channels clip (they appear pure black or white)...

Hey, learn something new every day. In PS I can adjust the individual clipping points for each of R, G, and B down in the shadows. This got rid of a slight color cast right before dead black. But ...

We have this in Curves, and in tonal corrections in LR and CR using the same modifier keys. ...

... I can't figure out how to do it in LR. The histogram in the Develop module seems dedicated to RGB -- is there a way to isolate the R, G, and B channels?

[digitaldog]

Hey, learn something new every day. In PS I can adjust the individual clipping points for each of R, G, and B down in the shadows. This got rid of a slight color cast right before dead black. But ...
... I can't figure out how to do it in LR. The histogram in the Develop module seems dedicated to RGB -- is there a way to isolate the R, G, and B channels?
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In LR you do this with Exposure and Black sliders.

A similar and useful kind of overlay is found using the same key commands in sharpening.

[ariaaudio]

In LR you do this with Exposure and Black sliders.

A similar and useful kind of overlay is found using the same key commands in sharpening.
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No doubt about it, holding ALT (Windows) when playing with LR's Exposure and Black sliders displays the clipped bits very clearly -- that's a great trick. But can you individually/separately adjust the clipping points of R, G, and/or B, or are all three channels locked together?

[digitaldog]

But can you individually/separately adjust the clipping points of R, G, and/or B, or are all three channels locked together?
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I'm not sure what you're trying to do. They are "locked". You mean you want to control each individually as a curve like you could do in Photoshop?

[ariaaudio]

I'm not sure what you're trying to do. They are "locked". You mean you want to control each individually as a curve like you could do in Photoshop?

In PS you can specify the R, G, and B channels in the Levels (or Curves) dropdown. On my test image it helped me get rid of a color cast in deep shadow where R and B had gone to 0 but G was still stubbornly holding onto a percent or two. The image was from a stage shot with stage lighting which had more darn colors from more darn directions than I can count and I was able to adjust, or equalize, the clipping points of the three color channels individually.
 
I was hoping the same trick -- independent channel clipping -- was available in LR w/o exporting to PS. But if they're locked, they're locked.

[digitaldog]

Black clipping is black clipping (all the values clip to R0/G0/B0. Values above might not but then where do you want to draw the line (everything short of an image of a gray card can't be R=B=G). I think you're worrying about something you shouldn't.

With Raw, you want to be white balancing anyway (due to how the data maps in a linear color space). White balance, set black clipping if you wish.

[ariaaudio]

I think you're worrying about something you shouldn't.

Wouldn't be the first time. . . .