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Author Topic: Lab color values in LR5  (Read 4568 times)
bns
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« on: June 29, 2013, 02:50:09 AM »
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A nice feature in LR5 is the possibility to 'measure' colors also in Lab values. For me that works more intuitively then RGB values while making color adjustments. It is a pitty however that while softproofing only RGB values are available. Or am I missing something?

Boudewijn Swanenburg
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PeterAit
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« Reply #1 on: June 29, 2013, 06:42:09 AM »
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I agree that LAB color should be on the list for LR6. Dan Margulis's book on LAB color in Photoshop had some useful techniques that I have not been able to replicate in LR.
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Peter
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john beardsworth
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« Reply #2 on: June 29, 2013, 07:31:14 AM »
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LAB color readout is in Lr5 - right click the histogram in Develop. I must say, I hope that's the end of it.

John
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bns
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« Reply #3 on: June 29, 2013, 10:14:21 AM »
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LAB color readout is in Lr5 - right click the histogram in Develop.....

Yes, but once one enables the softproofing mode, one is back to RGB values.
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Jim Kasson
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« Reply #4 on: June 29, 2013, 10:36:11 AM »
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I agree that LAB color should be on the list for LR6. Dan Margulis's book on LAB color in Photoshop had some useful techniques that I have not been able to replicate in LR.

If you're talking about changing the working space to Lab and exposing Lab editing to the user, it would be a complete change in philosophy for Lr, which tries to make the actual, under the covers, working space something the user doesn't have to think about.

Or maybe you mean something else. When you talk about Dan's book, it makes me think you want to edit Lab values. I guess you could do that and keep the linear ProPhotoRGB working space, but the trend in Lr controls is towards more visual editing and more proprietary algorithms.

Jim
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digitaldog
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« Reply #5 on: June 29, 2013, 03:12:54 PM »
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Yes, but once one enables the softproofing mode, one is back to RGB values.

Why on earth would you need Lab values in soft proof mode? You have it without when editing the master image which will go (where?). In Soft Proof you have on screen simulation AND actual output RGB values. Having Lab values isn't necessary or useful. Having the actual output values are.

To much of a love feast with Lab values, they can be useful to a degree, but not here.
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Andrew Rodney
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Tim Lookingbill
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« Reply #6 on: June 29, 2013, 03:23:36 PM »
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Ever look at a "Paint By Numbers" painting?

Every damn one of them looks like crap!

Why on earth would you want to edit according to the numbers? Do you know that LAB is not a uniformly perceptual color model meaning on some colors you can be off by 5 points in either channels and hardly see a substantial change while others can look grossly off by just 1-2 points.

Do an online search on "Color Constancy" and see where else going by the numbers can screw things up visually.

You have a color managed preview that was brilliantly engineered into the software and hardware so we wouldn't have to rely on exact numbers.

I'ld suggest you rely on that since you paid good money for it.
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bns
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« Reply #7 on: June 29, 2013, 03:31:20 PM »
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I thought that by being able to compare Lab values both before and after the softproof preview would make it easier to distinguish between required adjustments in hue or saturation or lightness.

Might of course be wishful thinking on my part. Thanks for the advice to believe my eyes rather then my brain.
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digitaldog
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« Reply #8 on: June 29, 2013, 03:38:51 PM »
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Might of course be wishful thinking on my part. Thanks for the advice to believe my eyes rather then my brain.

Don't feel bad, Lab has been way over sold. It was never designed for what the Lab proponents try to force it to do. Especially when they are told to convert into and out of Lab to 'fix' something they could do in RGB in the first place. It is a useful color model. It's real, real useful for defining color differences numerically. It is truly device independent but then RGB working space's are close enough and that's what is being used within LR. IF you are more comfortable viewing Lab values on the master image fine, but you can do that with an RGB working space values as well. When soft proofing, you are presumably done doing the heavy lifting and you now want to see a simulation of the output based on paper, ink, and contrast ratio and the effect of the rendering intent on the image in context. The numbers, RGB or Lab are not really useful, the idea of a soft proof is to allow you to see the output simulation before you make a print and if you wish, conduct very subtle corrections based on that view.

A good 90% if not all corrections from the god awful images illustrated in Dan's book, fixed using Lab could be fixed in RGB or better, just doing a better, less sloppy job of photography and raw processing (assuming any of those awful images were raw to begin with).
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PeterAit
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« Reply #9 on: June 29, 2013, 04:01:23 PM »
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LAB color readout is in Lr5 - right click the histogram in Develop. I must say, I hope that's the end of it.

John

Reading LAB values is of little use to most people. Manipulating them can be very useful. That's what I would like to have.
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Peter
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Tim Lookingbill
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« Reply #10 on: June 29, 2013, 04:18:09 PM »
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I thought that by being able to compare Lab values both before and after the softproof preview would make it easier to distinguish between required adjustments in hue or saturation or lightness.

The computer needs the numbers because it's a dumb machine and needs to be told what is meant by color for every pixel on the screen. Its algorithms make adjustments to each pixel in relation to each other as a continuous tone image (photo) NOT INDIVIDUALLY which is what I meant by the "Paint By Numbers" analogy.

It maps each individual pixel so it mixes together to form a realistic image which involves complex color adjustments under the hood to trick your eyes into seeing the image as a whole and as intended. If you zero in on one color in the image you now change the perception relationship which influences your eyes to adapt. For example if you zero in on just the red patch of the Color Checker chart it will change color. It does for me.

That chart was meant to be used as a standard measure using Lab coordinates for a computer to understand and adjust the color tables to create a camera profile. Direct examination of the chart can have Lab numbers substantially off where a human won't see a difference. It's just a guide for our eyes but a road map for the computer.

Graphic designers who create swaths of single color graphics in their page layouts to be viewed individually utilize Lab numbers just like a paint mixer at Home Depot uses to mix house paint to match existing paint. It's understood that single color is to be viewed without any other continuous tone elements such as a photo to change the perception of that one color.

Are you printing a graphic that must match a Pantone number CMYK can't reproduce? Then you need the Lab number equivalent to get the closest match possible. Photos are a completely different animal.
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Tim Lookingbill
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« Reply #11 on: June 29, 2013, 04:35:43 PM »
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And Dan's Lab edit processes take into account his "prepress color reproduction" experiences over the years of recognizing which image will work best using complicated Lab workflows. I cut my digital imaging teeth on his complicated channel mixing and Lab edit techniques back in '98 when I was teaching myself this new technology seeing there were no schools back then.

Yes you can get dazzling results using his processes but he's working from a mindset his students haven't been able to develop because as humans we first look...respond...change with edits as long as we know what that tool does to that certain part of an image.

The more complicated it becomes between "look and change" the slower the results. The slower the results, the faster the eyes adapt. The faster the eyes adapt the more the image has been changed to an outcome that hadn't had time to enter the mind at the outset because the user didn't understand what the tools were doing. That one process won't necessarily work on every image which will eventually make the user a slave at the computer because they've become enthralled with the process and not the results.

That's why folks fall in love with the process Dan puts forth but fail to properly see the image as others are seeing which often looks off.

You have to edit quicker than your eyes can adapt and change your perception of the image.

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digitaldog
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« Reply #12 on: June 29, 2013, 05:40:33 PM »
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Reading LAB values is of little use to most people. Manipulating them can be very useful. That's what I would like to have.

Will never happen in ACR/LR. It's an RGB engine.
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Andrew Rodney
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Schewe
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« Reply #13 on: June 29, 2013, 05:56:12 PM »
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Will never happen in ACR/LR. It's an RGB engine.

Well, ACR 8.1 allows you to set Lab as the working space–Thomas even invented an Lab histogram...course, the processing adjustments aren't in Lab :~) But you can open a raw image directly into Photoshop as an Lab color space.
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Tim Lookingbill
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« Reply #14 on: June 29, 2013, 06:01:25 PM »
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Well, ACR 8.1 allows you to set Lab as the working space–Thomas even invented an Lab histogram...course, the processing adjustments aren't in Lab :~) But you can open a raw image directly into Photoshop as an Lab color space.

Are you privy to the reasons why the engineers included Lab color space in ACR 8.1?
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Schewe
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« Reply #15 on: June 29, 2013, 06:22:32 PM »
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Are you privy to the reasons why the engineers included Lab color space in ACR 8.1?

Yes...Thomas decided that ACR should be able to process into any color space including Lab and CMYK and provide readouts and a soft proof of the output space–note ACR doesn't have a before/after capability (yet). Lightroom however, will still be limited to processing into RGB only color spaces.
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digitaldog
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« Reply #16 on: June 29, 2013, 06:47:02 PM »
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Well, ACR 8.1 allows you to set Lab as the working space–Thomas even invented an Lab histogram...course, the processing adjustments aren't in Lab :~) But you can open a raw image directly into Photoshop as an Lab color space.

During testing, when I saw this, I converted a few hundred color patches using ACR and the same in Photoshop, ran em though ColorThink and the results were absolutely identical, dE 0 for every patch. So Jeff, do you suppose ACR hands this off to Photoshop to convert?
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Andrew Rodney
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BartvanderWolf
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« Reply #17 on: June 29, 2013, 07:03:22 PM »
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Will never happen in ACR/LR. It's an RGB engine.

Thank goodness for that! Modern output modalities are also mostly RGB driven, and Lab is not absolutely perceptually uniform and it introduces color shifts during conversion.

Cheers,
Bart
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Vladimirovich
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« Reply #18 on: June 29, 2013, 07:15:28 PM »
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Are you privy to the reasons why the engineers included Lab color space in ACR 8.1?
they included it in ACR long time ago (using excursions to LAB for various purposes, wrote Eric Chan on May 24, 2011 in ColorSync mailing list = "ACR does use L*a*b* for some internal color difference estimates, e.g., for auto-calculated masks")... just ACR 8.1 now allows more than 4 output color spaces (including LAB).
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Vladimirovich
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« Reply #19 on: June 29, 2013, 07:17:04 PM »
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So Jeff, do you suppose ACR hands this off to Photoshop to convert?
ACR had all necessary Lab math in it long ago
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