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Author Topic: LAB COLOR  (Read 26506 times)
Wayne Fox
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« Reply #20 on: November 14, 2007, 10:48:53 PM »
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I understand and am quite used to people wanting to pontificate on a web forum, but what would be really nice is if someone would just actually answer my original question.
[a href=\"index.php?act=findpost&pid=152718\"][{POST_SNAPBACK}][/a]

I've read parts of his book and sat through a few of his demonstrations in Photoshop world.

At one time I used Lab as a noise reduction technique, but at this point I don't use Lab at all anymore. I guess I just don't run into problems where I"m looking for an answer and Lab seems to be one.
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TylerB
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« Reply #21 on: November 15, 2007, 12:00:56 AM »
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I still think some tool sets that have L,A,B controls, but work on the RGB file would be ideal for people who like to work with L,A,B numbers. Photoshop could covert on the fly between the tool L,A,B numbers and the RGB (or whatever) file. After all, it does it for the info pallatte seamlessly.
Not sure I'm explaining adequately, but makes sense to me. No space conversions needed.
Tyler
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bobrobert
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« Reply #22 on: November 15, 2007, 04:12:24 AM »
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It's L*, a*, b*...not LAB (it's ok to shorten to Lab but it ain't LAB).

See: Lab color space

Lab is fine for "certain" image corrections that can't be done in RGB or CMYK...but it ain't no magic bullet. Use it when and where appropriate. Also note that converting to Lab from RGB is _NOT_ lossless. There is a one time quantization error the first time you convert and Lab isn't very forgiving when working in 8 bit/channel.

And one wonders why ol' Dano loves Lab so much but calls Pro Photo RGB a "super-wide" color space and thinks it's dangerous.
[a href=\"index.php?act=findpost&pid=152630\"][{POST_SNAPBACK}][/a]

quote > On 16 bit/ channel images the quantization error is a non issue >unquote

Bruce Fraser in Image sharpening

I get the feeling that in this thread and others the dislike of Dan Margulis gets in the way of an objective discussion This a pity How long does it take to go to Lab and back A few seconds? I think that this is highlighted just to try and discredit him I am all for anyone that pushes the boundary because we all can learn from it Even the ones that don't admire him Me? I am sitting on the fence
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digitaldog
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« Reply #23 on: November 15, 2007, 07:51:54 AM »
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I also use the L chanel for contrast adjustments when I don't want to alter colours (could use luminance layer, but isn't adding a layer about the same amount of work as switching spaces?)

More work? You'd have to decide. Its certainly faster than going through two mode changes, causes no data loss and is in essence, a metadata like instruction that doesn't get applied to the underlying data until flattened or printed. Then you have the ability to apply layer masks. So its a heck of a lot more flexible. And in many cases, I'm referring to a blending mode (Fade) which doesn't even produce a layer if you don't want to go that route.

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I still think some tool sets that have L,A,B controls, but work on the RGB file would be ideal for people who like to work with L,A,B numbers.

IF you want to use Lab numbers (which I find totally non intuitive and vastly prefer LCH), the info palette will provide those numbers while you work in any color space you wish.
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Andrew Rodney
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Mark D Segal
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« Reply #24 on: November 15, 2007, 08:05:51 AM »
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I still think some tool sets that have L,A,B controls, but work on the RGB file would be ideal for people who like to work with L,A,B numbers. Photoshop could covert on the fly between the tool L,A,B numbers and the RGB (or whatever) file. After all, it does it for the info pallatte seamlessly.
Not sure I'm explaining adequately, but makes sense to me. No space conversions needed.
Tyler
[a href=\"index.php?act=findpost&pid=152974\"][{POST_SNAPBACK}][/a]

I'm not aware of which tools you have in mind, other than the info palette. Could you please tell us which tools can operate with L*a*b controls that do not require working in that colour space?

I do keep L*a*b as my secondary info read-out, because I find the information handy for measuring greys and colour casts.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
francois
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« Reply #25 on: November 15, 2007, 08:23:56 AM »
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I'm not aware of which tools you have in mind, other than the info palette. Could you please tell us which tools can operate with L*a*b controls that do not require working in that colour space?

I do keep L*a*b as my secondary info read-out, because I find the information handy for measuring greys and colour casts.
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Tyler was perhaps thinking to something like [a href=\"http://www.curvemeister.com/]Curvemeister[/url]?
« Last Edit: November 15, 2007, 08:24:21 AM by francois » Logged

Francois
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« Reply #26 on: November 15, 2007, 08:38:34 AM »
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I get the feeling that in this thread and others the dislike of Dan Margulis gets in the way of an objective discussion This a pity How long does it take to go to Lab and back A few seconds? I think that this is highlighted just to try and discredit him I am all for anyone that pushes the boundary because we all can learn from it Even the ones that don't admire him Me? I am sitting on the fence
[a href=\"index.php?act=findpost&pid=153002\"][{POST_SNAPBACK}][/a]

This discussion has nothing to do with that. People here are talking about the objective realities of the implications, potential and impacts of using one workspace relative to another. You're right - it only takes a jiffy to go back and forth between RGB and L*a*b, but if you read the material being discussed here, you will learn that there's a whole lot more to it than that. And if you read Dan Margulis's books carefully enough, you will also learn that even though he wrote a whole book about it, Dan does NOT recommend using L*a*b indiscriminately. One can legitimately argue about whether some of the problems he approaches with L*a*b cannot be more easily and effectively dealt with in other ways, and that is legitimate discussion without personalizing anything.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
TylerB
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« Reply #27 on: November 15, 2007, 12:54:02 PM »
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Quote from: MarkDS,Nov 15 2007, 09:05 AM
I'm not aware of which tools you have in mind, other than the info palette. Could you please tell us which tools can operate with L*a*b controls that do not require working in that colour space?

I never said I could write coherently.
I said I thought there was a need for such tools, and that they would not be difficult to implement, not that they yet exist.
Tyler
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TylerB
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« Reply #28 on: November 15, 2007, 12:58:14 PM »
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Tyler was perhaps thinking to something like Curvemeister?
[a href=\"index.php?act=findpost&pid=153050\"][{POST_SNAPBACK}][/a]


looks like the deal.
Frankly I'm happy with RGB, but so many people have told me they like LAB based editing...
I'll pass this on.
Tyler
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digitaldog
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« Reply #29 on: November 15, 2007, 01:00:28 PM »
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I said I thought there was a need for such tools, and that they would not be difficult to implement, not that they yet exist.
Tyler
[a href=\"index.php?act=findpost&pid=153124\"][{POST_SNAPBACK}][/a]

You want tools that you can't describe what you want them to do?

Just what problems are you having that you can't currently fix with the current tool set? And why are you doing this in Photoshop, at least globally instead of in the Raw converter or scanner driver?
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Andrew Rodney
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TylerB
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« Reply #30 on: November 15, 2007, 01:04:24 PM »
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You want tools that you can't describe what you want them to do?

Just what problems are you having that you can't currently fix with the current tool set? And why are you doing this in Photoshop, at least globally instead of in the Raw converter or scanner driver?
[a href=\"index.php?act=findpost&pid=153132\"][{POST_SNAPBACK}][/a]


forget I dropped by, either I can not write or others can't read, or both.
Tyler
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Mark D Segal
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« Reply #31 on: November 15, 2007, 01:19:33 PM »
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Quote from: TylerB,Nov 15 2007, 01:54 PM
Quote from: MarkDS,Nov 15 2007, 09:05 AM

I said I thought there was a need for such tools, and that they would not be difficult to implement, not that they yet exist.
Tyler
[a href=\"index.php?act=findpost&pid=153124\"][{POST_SNAPBACK}][/a]

OK, now that I re-read you, the expression "would be ideal" kind of  acknowledges that there are no such tools yet. We're now clear on that. As to the next point "would not be difficult to implement" - how do you know that? I sure don't, but I can't imagine the programming being easy unless I knew exactly what it is we are trying to program and then had the kind of understanding of the digital imaging mathematics and programming needed to pull it off. We do tend to take alot for granted because those guys in Adobe are real bright - but even they have their limits! (one would think).

Andrew's point is right-on the money as a serious a priori. Any one who wants new features in Photoshop needs to make a case, as Jeff Schewe has pointed out to us in the past - that the feature would provide real value added to the application and to a community of users. Given the existing feature sets in CR4.1 and CS3, that's a high bar. I don't take Andrew's comment as an invitation not to drop by, but more as a pause for reflection. LAB, CMYK, RGB are just colour spaces. There's nothing magic about any of them. They each have their strengths and limitations, as Dan Margulis himself has explained. There's no point people saying they want to work in L*a*b for the sake of working in L*a*b - you go there when it's the preferred thing to do for a problem at hand.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
JeffKohn
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« Reply #32 on: November 15, 2007, 03:29:35 PM »
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Look, I have no issues rendering global tone, color and saturation (among other things) from Raw to produce the color appearance I want to represent.
To me, saturation/vibrance is not something I want to work with globally, without some control over how it's applied. But if you're happy with a single global control, by all means keep using it.

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I don't need to use a blend if and jump through all kinds of hoops. Just because you have layers, blend modes and so forth, doesn't mean you have to go through a 38 step, convoluted process. You might, it may be 3 steps but as yet, I haven't found the need. I like to practice KISS.
You're making it sound so complicated, but it's not. I have a few actions I use as a starting point, so it's just a click or two, then I can fine-tune from there if I want. But I'm not a wedding/event/sports photograph who needs to process thousands of images a week, either. If I were, maybe I'd just stick with the controls in Lightroom. But I tend to put a little more time into my images and I'm perfectly content to do so. Lab is a very useful tool in my toolbox, and a few extra clicks to do the conversion is a complete non-issue from a workflow standpoint.

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There's no reason to sharpen the L channel either, another exercise in time loss and data loss. Just run the sharpening and fade luminosity. Is it 100% identical? No but it addresses the problem you're going after in Lab, color fringing. Its faster, it causes a lot less data loss AND you have the opacity slider to boot
I said point-blank in my first post that I wouldn't make the trip to Lab just for sharpening. But if I'm going to Lab anyway, I do my sharpening there. Data loss from Lab conversion is a non-issue for 16-bit images, and since I sharpen a duplicate layer I have the same opacity/masking/blend-if options as your luminosity blend mode in RGB.

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Lab has a role in image processing. But as I said, its recently become the big macho color space for doing anything and everything according to Dan. If he would spend just a little time looking at Raw rendering (instead of slamming it or trying to teach how to polish turds using Photoshop), his ideas might be easier to swallow. He sees everything from the perspective of a hammer in which every image correction (NOT rendering) is a nail.
I'm not a Dan disciple, I disgree with him on things like 16-bit, wide-gamut, etc. And I agree that a  lot of the stuff in later sections of his Lab book a bit silly and does seem to involve polishing turds. However I do find the techniques in the early chapters very useful.

It sure seems like your position on Lab is at least partly tied into your personal dislike of Dan.
« Last Edit: November 15, 2007, 03:31:49 PM by JeffKohn » Logged

digitaldog
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« Reply #33 on: November 15, 2007, 03:38:43 PM »
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It sure seems like your position on Lab is at least partly tied into your personal dislike of Dan.
[a href=\"index.php?act=findpost&pid=153164\"][{POST_SNAPBACK}][/a]

Perhaps. I'm more inclined to dislike unnecessary data loss and time lost producing results I can get without either. As I said, there is a role for some Lab processing as there are steps one can provide in CMYK that can't be done in RGB but they are few and far between. I prefer to do steps in the most appropriate color space and since all input devices produce RGB, I prefer to stay there as long as possible. That's why I think the Lab message is way oversold, the Raw rendering message undersold (it is kind of a new message anyway).
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Andrew Rodney
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JeffKohn
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« Reply #34 on: November 15, 2007, 05:57:40 PM »
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I'm more inclined to dislike unnecessary data loss...
For a 16-bit image, the data loss from a round-trip to Lab is so small as to be largely theoretical. Can you honestly tell me you think it's going to result in visible degradation of the image?

Just about anything you do in Photoshop is going to result in some data loss, but I'm more concerned with getting the image to look how I want, rather than whether I was able to preserve 99.3% versus 99.0% of the levels from the original raw conversion.

You're obviously a proponent of doing as much as possible in the raw convertor. To a certain extent I agree, and I think Dan's opinion on setting WB and overall tonality in the raw convertor are just a silly old dog refusing to learn new tricks. But some of the tools in ACR (clarity, vibrance, sharpening, NR) are still fairly crude compared to equilavalent techniques in Photoshop. To use a tool that produces inferior results just because it theoretically preserves more numerical data kind of misses the point IMHO.
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digitaldog
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« Reply #35 on: November 15, 2007, 06:02:43 PM »
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For a 16-bit image, the data loss from a round-trip to Lab is so small as to be largely theoretical. Can you honestly tell me you think it's going to result in visible degradation of the image?

In 16-bit, no. But it is a bigger file, it will take longer. But in high bit, not an issue.
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Andrew Rodney
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luong
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« Reply #36 on: November 15, 2007, 07:20:33 PM »
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Here is an interesting use of Lab suggested by photographic artist Chris Jordan, which cannot be done easily in RGB:
http://www.largeformatphotography.info/for...ead.php?t=19014
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tad
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« Reply #37 on: November 15, 2007, 10:13:08 PM »
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Let me sum up the previous posts:

1. The majority of those who responded do not use l*a*b* (hope the asterisks are correct)
2. Those who don't give time as a reason.
3. Those who do, hardly  explain why, when or, how.

This has been very informative.
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Wayne Fox
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« Reply #38 on: November 16, 2007, 05:13:39 PM »
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Let me sum up the previous posts:

2. Those who don't give time as a reason.

[a href=\"index.php?act=findpost&pid=153233\"][{POST_SNAPBACK}][/a]

Seems to me those that don't use Lab are -

1.  Afraid of data loss, especially with 8 bit files
2.  Believe you can do the same thing easier, as well, less destructively and with more flexibility during the RAW conversion or with normal photoshop tools.
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skid00skid00
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« Reply #39 on: November 16, 2007, 10:24:20 PM »
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I use LAB to white balance jpgs, and to do very strong chrominance noise reduction.
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