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Author Topic: Lab color values in LR5  (Read 4068 times)
Tim Lookingbill
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« Reply #20 on: June 29, 2013, 08:30:17 PM »
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ACR had all necessary Lab math in it long ago

Except the previewed edits are driven by ACR's color engine, not Lab's. What goes on under the hood mathematically is for the code warriors to be concerned about, not photographers.

All I know is charcoal neutral or dead looking shadows, dreary cool and warm tertiary colors next to sappy saturated key fills are not a desirable look as I've seen in other Raw converters that use Lab as a color engine.
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Schewe
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« Reply #21 on: June 29, 2013, 09:19:45 PM »
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So Jeff, do you suppose ACR hands this off to Photoshop to convert?

Nope...but since Thomas wrote ACE I would expect both ACR and Photoshop to produce the same results with color transforms...in fact, I would be surprised if there were different results!

The thing I was hoping for (which hasn't happened "yet) is the ability to import DNG files directly into Illustrator and InDesign. You can do that now by setting the Workflow Options setting to CMYK and then open as a raw Smart Object into a TIFF or PSD CMYK document and then place that in InDesign (I've tested this and it works). You can go back to the Smart Object and modify the ACR settings and update them into InDesign. So, the ability to output in any color space is, intriguing...but bleeding edge. None of which is on the table for Lightroom...
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Vladimirovich
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« Reply #22 on: June 30, 2013, 01:09:13 AM »
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Except the previewed edits are driven by ACR's color engine, not Lab's.

and what is "Lab's" color engine, if you don't mind ?


What goes on under the hood mathematically is for the code warriors to be concerned about, not photographers.

as I've seen in other Raw converters that use Lab as a color engine.

such as ?

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Tim Lookingbill
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« Reply #23 on: June 30, 2013, 12:47:49 PM »
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and what is "Lab's" color engine, if you don't mind ?


What goes on under the hood mathematically is for the code warriors to be concerned about, not photographers.

such as ?



Here ya' go. A comparison demonstrating the two color engines on the same Raw PEF file below. I applied the same color temp settings and attempted to get each rendering to match as much as possible.


Note the lack of color (Charcoal neutral) in the shadows of of the leaves and the differences in actual dark colored leaves. I can use Adobe Standard color profile to get a similar effect but even still there's more depth because that profile still injects some kind of color even though it has a neutralizing effect throughout the color tables of the image.

This has a lot to do with psycho-optical effects similar to psycho-accoustics involved with human perception. This is typical color grading I see in a lot of Dan Margulies' final Lab processes posted in forums by those that process images in Lab. Those charcoal shadows tend to make inkjets render shadows with a lot of black ink which looks like crap next to vibrant colors on a print.

Just a note:

I prefer not to mention the Raw converter used for the Lab engine version because I respect the guy's efforts in creating a Raw converter with so many other features and preview renderings mainly having to do with sharpening and noise reduction appearance. He also keeps up religiously with updates and getting back with emails. I just like ACR's workflow simplicity and previews better.
« Last Edit: June 30, 2013, 12:53:36 PM by Tim Lookingbill » Logged
Vladimirovich
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« Reply #24 on: July 01, 2013, 09:00:04 AM »
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I prefer not to mention the Raw converter used for the Lab engine version because I respect the guy's efforts in creating a Raw converter with so many other features and preview renderings mainly having to do with sharpening and noise reduction appearance. He also keeps up religiously with updates and getting back with emails. I just like ACR's workflow simplicity and previews better.

if you can't name a software then you shall probably refrain from using that as an argument and you shall refrain from generalizing on top of that... in addition what you comparison demonstrates exactly ? some unknown conversion (parameters wise) using unknown software ? there was one PhD here who compared iphone (?) jpg w/ results of the raw conversion from MFDB trying to prove some point...
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Tim Lookingbill
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« Reply #25 on: July 01, 2013, 01:30:59 PM »
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if you can't name a software then you shall probably refrain from using that as an argument and you shall refrain from generalizing on top of that... in addition what you comparison demonstrates exactly ? some unknown conversion (parameters wise) using unknown software ? there was one PhD here who compared iphone (?) jpg w/ results of the raw conversion from MFDB trying to prove some point...


It's Iridient Developer and I was told by the developer he uses Lab as its color engine. This look is not confined to just this Raw converter but in Lab edits generally speaking as I indicated above.

Now, I'll go on to tell you why I'm right about editing in Lab.

The crux of the matter with Lab was mentioned several times here at LuLa about how well its saturation edits behave "better" than applying in an RGB space, the behavior of which stems from the fact Lab applies saturation by degrees according to how close a color is to absolute gray=(R=G=B/0=a*,0=b*). That's a problem with regards to the adaptive nature of human perception and how we view a scene in accordance with the actual definition of the function of a saturation boost.

What is happening when saturation is being increased?

It's not defined by science as "Make my picture look pretty" slider. Its function is to mimic the spectral reflectance characteristics of full spectrum light on any given object lit by it that we "FEEL" (from memory) is missing in the image. Shadows as defined by lab and a spectro technically exhibit less spectral reflectance and are closer to gray thus should get less saturation.

But we humans don't look just at shadows when we view an entire scene. I have looked just at shadows and some are quite neutral, some are bluish, some are greenish, etc. But they change color in relation to when I view the entire scene because the surrounding other spectral reflectance driven colors induce the adaptive effect.

Also saturation levels especially bumped up high also induce the adaptive effect into seeing less saturation scanning individual areas of an image. Lab does not calculate for this effect under the hood. It was built defining color one color at a time just like a machine (spectro) defines color which is how a machine can only understand color BY THE NUMBERS, just like a digital sensor defines color by measuring voltage variation of charged pixel cells to define gray luminance for each RGGB combination.

Lab only cares about the numbers when increasing saturation when the data is farthest away from gray not taking into account how a human sees the entire scene which is greatly influenced by adaption by both saturation levels and overall color in the scene.

Like I indicated with the Color Checker Chart when a human zeros in on just one color patch the adaptive effect kicks in and changes the color appearance by comparison to looking at the entire chart as a whole object viewing all the patches at once.

Shadows can be many colors some R=G=B and some not. Some may look neutral but read R>G>B and vice versa. Lab doesn't care what you see. If it's gray by the numbers it doesn't increase saturation. If it is colored it will increase saturation whether it needs it or not. See the example below and manipulation of the appearance of shadows in relation to its numbers.

Which one looks neutral? Which one will increase in saturation equally in relation with the rest of the image if applied either in Lab or in an RGB space?

« Last Edit: July 01, 2013, 01:36:40 PM by Tim Lookingbill » Logged
BartvanderWolf
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« Reply #26 on: July 01, 2013, 01:41:41 PM »
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The crux of the matter with Lab was mentioned several times here at LuLa about how well its saturation edits behave "better" than applying in an RGB space, the behavior of which stems from the fact Lab applies saturation by degrees according to how close a color is to absolute gray=(R=G=B/0=a*,0=b*). That's a problem with regards to the adaptive nature of human perception and how we view a scene in accordance with the actual definition of the function of a saturation boost.

Hi Tim,

Lab was never designed as an editing space, but more as a colorspace that allowed to judge neutral colors. For Editing, something like CIECAM 2002 is much better, and RawTherapee offers just that as one of the Tonemapping functions. It is very effective for believable saturation and contrast adjustments and it can be adjusted for different viewing (brightness) conditions.

Cheers,
Bart
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Vladimirovich
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« Reply #27 on: July 01, 2013, 02:12:40 PM »
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It's Iridient Developer and I was told by the developer he uses Lab as its color engine.



you mix using a specific color space for postdemosaick postprocessing and how a specific software is implementing for example "saturation"... why do you think Adobe's profiles have hue twists ( http://dcptool.sourceforge.net/Hue%20Twists.html ) ?
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Vladimirovich
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« Reply #28 on: July 01, 2013, 02:17:10 PM »
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For Editing, something like CIECAM 2002 is much better, and RawTherapee offers just that as one of the Tonemapping functions.
but it is not an internal working colorspace there - it is just a space used for a specific tool... it is unlike RPP using upLab internally post demosaick, while exposing Lab readouts in its UI and exporting image in Lab (as an option, in addition to RGB colorspaces or RGB w/o a "colorspace")... RPP is said to use Munsell inside for its next release.
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Tim Lookingbill
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« Reply #29 on: July 01, 2013, 04:03:22 PM »
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you mix using a specific color space for postdemosaick postprocessing and how a specific software is implementing for example "saturation"... why do you think Adobe's profiles have hue twists ( http://dcptool.sourceforge.net/Hue%20Twists.html ) ?

Yeah, I already know about hue twists in Adobe profiles.

What's that got to do with what I said about editing in Lab? Or did you understand about that Gray=White Balance=doesn't get saturated?

Perceived neutrals in an RGB color space are detached from color temp appearance when applying saturation as it should be according to human perception which in nature there's really no such thing as R=G=B/a*=0,b*=0 as well as it having any connection to an illuminant. But Lab stays strictly by the numbers anyway.

We define neutral by only one illuminant=D50 in Lab. Do you know how many hues there are to white and gray in nature?

Don't know how to make it any clearer to you.

BTW when I brought up this subject to Brian Griffith, the developer of Iridient Developer, he agreed with me and said it was the reason he included RGB curves as a way to correct for it. ACR includes Split Tone but I only use that for color effects OR...wait for it...HUE TWISTS! OMG!
« Last Edit: July 01, 2013, 04:13:25 PM by Tim Lookingbill » Logged
Vladimirovich
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« Reply #30 on: July 01, 2013, 04:13:21 PM »
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Yeah, I already know about hue twists in Adobe profiles.
so what do you think they need that ?
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Tim Lookingbill
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« Reply #31 on: July 01, 2013, 04:20:20 PM »
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so what do you think they need that ?

I guess you'ld have to ask them.

But my guess based strictly on observing Golden Hour lit highlights that are orange-ish with a regular custom DNG profile but turn a dull reddish brown yellow hue switching to Adobe Standard may have something to do with clipping. At least that's what happens when I switch to Adobe Standard profile and I don't know if that one includes a hue twist.

This hue twist thing hasn't really affected any of my images or at least I don't notice it when it happens. If I get funky hue twists to highlights I just use Split Tone or the HSL hue slider or Color Temp slider. Geez! So many tools to fix one little thing. Why would the Adobe engineers do such a thing? It's scandalous I tell you!
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digitaldog
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« Reply #32 on: July 01, 2013, 04:20:40 PM »
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so what do you think they need that ?

Doesn't present a problem for many of us. What's that got to do with Tim's comments on Lab?
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Andrew Rodney
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Tim Lookingbill
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« Reply #33 on: July 01, 2013, 04:42:59 PM »
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Hi Tim,

Lab was never designed as an editing space, but more as a colorspace that allowed to judge neutral colors. For Editing, something like CIECAM 2002 is much better, and RawTherapee offers just that as one of the Tonemapping functions. It is very effective for believable saturation and contrast adjustments and it can be adjusted for different viewing (brightness) conditions.

Cheers,
Bart

Thanks for the suggestion, Bart, but I'm quite happy with the way things are working with my current ProPhotoRGB workflow with ACR and now Lightroom 4 when I get the chance to dive into learning that app and sort out its catalog/library messing around with my existing xmp edited files in Bridge.

Vlad,

Is this the hue twist you're referring to that I described about Adobe Standard profile?
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Vladimirovich
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« Reply #34 on: July 01, 2013, 04:54:55 PM »
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Doesn't present a problem for many of us. What's that got to do with Tim's comments on Lab?
because he was effectively stating that great RGB engine does not need external crutches, his Lab issues apparently does not present a problem for many of others...
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Tim Lookingbill
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« Reply #35 on: July 01, 2013, 05:06:59 PM »
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Quote
...his Lab issues apparently does not present a problem for many of others...

Problems with color perception are quite subjective, aren't they?

In art there's no accounting for taste as I saw first hand at portraits of pale complected children with rosy cheeks shot outdoors and processed in Lab space. The highlights of their skin looked normal but the modeled shadows transitioning to the side of their face away from the light looked like they were dusted or airbrushed in charcoal.

That's what I see in a lot of finished images in forums that discuss the wonders of processing in Lab space. Every darn one of the contributors said the Lab processed images look so much better than when they were processed in RGB.

That sounds like a religion to me. But again, there's no accounting for taste.
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Vladimirovich
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« Reply #36 on: July 01, 2013, 05:16:03 PM »
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That's what I see in a lot of finished images in forums that discuss the wonders of processing in Lab space. Every darn one of the contributors said the Lab processed images look so much better than when they were processed in RGB.

That sounds like a religion to me. But again, there's no accounting for taste.

I don't say that, I say I saw many images that I wish were mine from LR, ACR, Iridient, SilkyPix, RPP, DPP, CaptureNX, you name it (even OOC JPG, when sufficiently downsized for visual consumption)... and I saw the same share of "bad" images from the same converters...
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Tim Lookingbill
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« Reply #37 on: July 01, 2013, 06:02:48 PM »
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I don't say that, I say I saw many images that I wish were mine from LR, ACR, Iridient, SilkyPix, RPP, DPP, CaptureNX, you name it (even OOC JPG, when sufficiently downsized for visual consumption)... and I saw the same share of "bad" images from the same converters...

But how could you attribute the color space edited in as the influence on why you wished those images were yours without a comparison?

Each image is going to present some kind of non-normalcy from the outset or else why would they need editing. What I'm saying is edits in Lab to get the image to look normal always have that non-normalcy I just describe above.

And what non-normalcy could you spot that constitutes "bad" images. Any visual descriptions?
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Tim Lookingbill
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« Reply #38 on: July 01, 2013, 06:16:52 PM »
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Do you know where I just love the way the Lab color model works?

When I eyeball calibrated my first HDtv.

After I neutralize and apply a warmer white balance to my B&W movies after first setting the Saturation slider to zero all the way so all channels are in B&W, I can increase the Saturation slider to a level that makes color content look great but doesn't increase the saturation of the warmer white balance of my B&W movies.

B&W movies don't exist in nature so they aren't part of the human color perception model, but it sure works for calibrating a machine. That's when I love the way Lab works...on a machine.
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