Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: tad on November 14, 2007, 12:02:19 am
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Just finished Photoshop LAB Color by Dan Margulis. I found it fascinating and was wondering if, when and why anyone employs LAB color in their workflow? I applied some of the methods to some of my landscape photos and was very impressed with the outcome.
If this belongs in the beginners forum I apologize.
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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 (http://en.wikipedia.org/wiki/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.
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Well, I use Lab all the time, practically on a daily basis, particularly on provided stock images, but on my own as well. I'd say about fifty percent of what I do goes through Lab at some point. The theory put forth by so many would suggest that converting to Lab is too destructive is just that, theory. After converting hundreds if not more images, the only ones that showed any type of visible degradation were those that were screwed up to begin with. There are so many other things to worry about than a few lost llevels. As far as why Dan uses Lab and doesn't particularly care for ProPhoto RGB, you'll have to read his book. The answers are all in there, very clearly at that. Lab Color has to be the single best book in digital imaging I've ever read. Dan pushes the envelope with the way he thinks more than any other imaging author and challenges the reader to do the same for him or her self.
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Jeez - I'm running for cover!!!
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or it can be written as CIELAB
it should always be CIE 1976(L*a*b*) or L*,a*,b*
but it not correct to shorten it to Lab
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For an alternative perspective on the 8 bit versus 16 bit debate, and Dan's position, this page (http://www.brucelindbloom.com/index.html?DanMargulis.html) on Bruce Lindbloom's site offers another view, which is worth reading even if you don't agree with it.
I think the bottom line is to use whatever workflow gives you the results that you (and your clients) want, even if the theory doesn't agree with what you're doing. OTOH, if you aren't happy with your results, be prepared to seek the knowledge of others.
FWIW, I use 16-bit ProPhoto RGB for RAW conversions, as well as subsequent editing in Photoshop. Currently, printing paths in Windows GDI are limited to 8 bits per channel, but this limit will probably be raised when the new Vista colour management gets exploited by printer driver writers. So at least I'm prepared for that.
One feature of colour management that I've discovered time & time again, over several years of learning about it, is that you can get to a point where you're happy with your workflow, and think you have a sufficient understanding of it, then along comes a new fact out of the blue that makes you realise that you don't understand it after all. Like using Adobe RGB as my PS workspace, then reading an article by Bruce Fraser a couple of years ago that reported (I'm writing from memory here as I can't find the article) that this particular space is poor at representing dark greens and browns. At this point I switched to ProPhoto RGB as well as 16 bits (because PS CS supported 16 bit layers etc.).
Regards,
Alan
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Hey TAD,
I can't resist a response on this one. Making a wish and getting an instant answer from God is what happened on this post. ...and SCHEWE came down and said...
I think Lab is great when you want to fiddle with with the Luminiance, the light and dark, in an image.
So I'm going to add a question, and maybe Schewe will answer me too.
When is it worth taking an image to Lab? Seriously.
wollom
(Tad did say he/she was a beginner, remember?)
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What is useful is to see what the LAB color model is based and really used for, how large a color space it is, what happens when you convert (ugh) 8-bit RGB to Lab and back, plus the time it takes and when you can avoid all these issues by using the lumonisty blending modes in Photoshop.
Lab certainly has a place in image processing. But its been way over blown. Its primarily become the poster child for one author who, as Jeff said, thinks its super cool but has no issues dismissing ProPhoto RGB as 'dangerous'. So what he says should often be taken with a grain of salt.
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FWIW, I use 16-bit ProPhoto RGB for RAW conversions, as well as subsequent editing in Photoshop. Currently, printing paths in Windows GDI are limited to 8 bits per channel, but this limit will probably be raised when the new Vista colour management gets exploited by printer driver writers. So at least I'm prepared for that.
A little OT but OS X 10.5 apparently has this functionality. Jeff, can we talk about what's coming from you know who, the printer company (and the need for application support for 16-bit printing)?
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I apologize profusely for my obvious ignorance and the incorrect use of "LAB" in my request for further knowledge in image processing. I can only hope for forgiveness and that the moderators allow me to remain an active participant on this forum.
In the future, if I am still allowed here, I will remain in the beginners section until my vocabulary and word usage is up to par with that of the more senior members.
Always grateful,
Tad
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The theory put forth by so many would suggest that converting to Lab is too destructive is just that, theory. After converting hundreds if not more images, the only ones that showed any type of visible degradation were those that were screwed up to begin with.
I would agree that all image correction involves data loss. One issue I have with Dan is that:
A. He dismisses this, especially high bit workflows when he (or we) never know when an image will break.
B. The output is rarely if ever defined. You can wonk on an 8-bit image going to a halftone dot till the cows come home and never see the effect (everything to Dan is this output) and really hose output to a fine ink jet or Contone printer.
C. It takes time to do the conversions on big files and often, you can produce the same effects visually in less time, with more post processing control using blending modes.
As for the data loss, its a fact, not a theory. Here's a test Richard Wagner did that I believe he tried or maybe actually got through the heavily moderated ACTL of Dan's:
OK, some preliminary results. All image conversions were done in PS
CS2. Where appropriate, conversions were made using RelCol and BPC,
with no dither. Image level counting was done using Levels 1.2,
©2001 Bruce J. Lindbloom, running under Classic 9.2 on Mac OS
10.4.7. The test file was the 8-bit 4096 x 4096 pixel image
containing all unique colors provided by Bruce Lindbloom via his web
site. http://www.brucelindbloom.com/index.html?RGB16Million.html (http://www.brucelindbloom.com/index.html?RGB16Million.html)
This is a good file to start with, as it does not contain JPEG
artifacts and it has not been previously subjected to profile
conversions that might bias the results.
Original Image:
File Name: RGB16Million.tif
Image Dimensions: 4096 x 4096 = 16,777,216 pixels
Color Type: RGB
File Format: TIFF
Bits/Channel: 8
Color Space: sRGB (assigned in PS CS2)
There are 16,777,216 unique colors in this image.
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Convert the above image to Lab:
There are 2,186,765 unique colors in this image.
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Convert the Lab image back to sRGB:
There are 2,186,295 unique colors in this image.
Note that this data matches very closely what is presented on Bruce
Lindbloom's site. I'm not sure why the slight difference - changes
in the CMM? Also, as he stated, "back and forth" trips to Lab do not
result in increased image degradation. It is primarily the first
trip to Lab that results in quantization loss. I have confirmed
this. (additional data not shown.)
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OK, how about Adobe to Lab? Better than sRGB, as I predicted in a
previous post.
There are 3,135,822 unique colors in this image.
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And ProPhoto to Lab - should be better yet - and it is. As expected,
moving from a wide-gamut color space to Lab results in less
quantization loss than moving from sRGB to Lab.
There are 6,236,954 unique colors in this image.
==========
In testing some of my own scanned wildlife images, the quantization
loss was frequently around 50% - 70% when converting from AdobeRGB to
Lab. For example, a 14-bit scan of a Kirtland's Warbler began with
18,617,959 unique colors; conversion to 8-bit resulted in 513,680
unique colors, and conversion of that image to Lab resulted in
279,760 unique colors.
Is any of this significant? In looking at the images, it doesn't
appear to be, although the same can be said for many other operations
that result in data loss. It is not clear what effect this may have
on an image if many operations follow. Avoiding the transition to
Lab avoids the data loss, although this obviously gives up the
advantages tof techniques unique to Lab.
--Rich Wagner
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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.
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Just finished Photoshop LAB Color by Dan Margulis. I found it fascinating and was wondering if, when and why anyone employs LAB color in their workflow?
I dont. Never. Because I get the results I want without it.
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I dont. Never. Because I get the results I want without it.
[a href=\"index.php?act=findpost&pid=152721\"][{POST_SNAPBACK}][/a]
Ditto. I do all the heavy lifting of tone and color rendering in a Raw converter. As such, I'd say 98% of all global work is done, I use Photoshop for local corrections and as yet, haven't seen any reason to convert to Lab for that. Hope that answer the OP question.
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When is it worth taking an image to Lab? Seriously.
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When you need to work on the color separately from the luminance or you need to adjust the contrast of the color separately from the luminosity. The ab channels (not unlike HSL or HSB) give a totally different impact when using Photoshop's tool set...
On the other hand, I would never really go into Lab for the purpose of working only on the luminosity as I've found the L channel so close to the luminance blend mode that it ain't worth the conversion to Lab.
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I'd like to hear some focused discussion on this as well.
Take the example of steepening the a/b curves (or is that a*/b*, or A, B or ...) to "enhance color" (sorry, that's probably not the "correct" term either). Say you even do this on a copy image that you selectively reveal, layered in your "original" 16bit ProPhoto file. What is a better way to accomplish this manipulation without going to... let me see... L*, a*, b*?
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I'd use Vibrance in Lightroom. This would be totally non destructive, instruction based rendering. I could make alterations to this (and iterations) without taking up more than a few k's of disk space.
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I'd use Vibrance in Lightroom. This would be totally non destructive, instruction based rendering. I could make alterations to this (and iterations) without taking up more than a few k's of disk space.
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Vibrance is not nearly as flexible. Working with the a/b curves you can steepen one more than the other, you can also use blend-if to limit the effect from colors that are already saturated. I do this to some extent for almost every landscape/nature image I postprocess, it's an invaluable tool in my workflow. I also sharpen the L channel while I'm there, although I wouldn't make the trip to Lab just for that.
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Vibrance is not nearly as flexible. Working with the a/b curves you can steepen one more than the other, you can also use blend-if to limit the effect from colors that are already saturated. I do this to some extent for almost every landscape/nature image I postprocess, it's an invaluable tool in my workflow. I also sharpen the L channel while I'm there, although I wouldn't make the trip to Lab just for that.
[a href=\"index.php?act=findpost&pid=152785\"][{POST_SNAPBACK}][/a]
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. 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.
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.
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.
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Before LR/CR4.1, I found it sometimes worthwhile converting an image to L*a*b for enhancing colour separation and saturation. It is also correct that the Blend IF sliders worked on the *a* and *b* channels in Layer Styles help very much to target and control the impacts. (But for luminance work, as observed above, one is just as well off using the RGB composite curve in Luminosity Blend Mode). At the same time, it must be said, this L*a*b is not an easy space to work with - takes alot of experience learning to control it and to predict what various curve moves will do, because it is anything but intuitive. It is also inconvenient making trips back and forth between colour spaces because Adjustment Layers cannot be preserved, so the workflow needs to be organized around trips to Lab in a way that avoids that inconvenience. (Here I'm ignoring the loss of information associated with colour space exchanges because that has already been well demonstrated and thoroughly discussed.) Hence all these very obvious and practical factors taken into account, if there are easier, non-destructive ways of achieving the same results without exchanging colour spaces, so much the better. LR and CR4.x have vastly increased this capability, not only because of the Vibrance and Clarity controls in the Basic Tab, but also because of the 24 independent targeted controls one has in the HSL Tab for eight colour groups of significant interest to photographers. To sum-up a short answer to the OP's question: do as much as the new (and old) tools allow in LR/CR4.x and CS3 before moving to L*a*b, and if you still find you need a particular effect just not otherwise achievable, go ahead and try L*a*b, but be mindful of the workflow implications.
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After reading the book I found Lab to be a very useful tool, I can do things that I cant seem to achieve in other colour spaces. These mainly involve modifying specific colours or help in making selections in an image. 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?) I understand it is just a part of the whole range of tools available in photoshop and as always there are a number of ways to do a lot of things, and which method is "preferred" is subjective or at least the subject of sometimes rigorous debate . I found some of the workflows in Dan's books very practical, its a pity he has to waste so much text space defending his methods, after all diversity is good! I am not a lightroom user so I am not sure how that would affect my opinions. I am looking forward to receiving RWCR CS3 so I can get up to speed on what Camera Raw has to offer. I think Dan's book is about utilising photoshop for image adjustments, not about what could be achieved in other programs like Lightroom. Its a very detailed book so I can't imagine coming to grief applying the methods if you understand the text, but it does take a while to get used to it.
David
I found it fascinating and was wondering if, when and why anyone employs LAB color in their
[a href=\"index.php?act=findpost&pid=152622\"][{POST_SNAPBACK}][/a]
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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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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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It's L*, a*, b*...not LAB (it's ok to shorten to Lab but it ain't LAB).
See: Lab color space (http://en.wikipedia.org/wiki/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.
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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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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.
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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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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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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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.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=153047\")
Tyler was perhaps thinking to something like [a href=\"http://www.curvemeister.com/]Curvemeister[/url]?
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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
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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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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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Tyler was perhaps thinking to something like Curvemeister (http://www.curvemeister.com/)?
[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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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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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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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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forget I dropped by, either I can not write or others can't read, or both.
Tyler
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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
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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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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.
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.
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.
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.
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It sure seems like your position on Lab is at least partly tied into your personal dislike of Dan.
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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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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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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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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 (http://www.largeformatphotography.info/forum/showthread.php?t=19014)
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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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Let me sum up the previous posts:
2. Those who don't give time as a reason.
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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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I use LAB to white balance jpgs, and to do very strong chrominance noise reduction.
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Scott Kelby, in The Photoshop Channels Book, says he uses Lab when he wants to add detail and vibrance to his images, especially landscapes. He adds that he uses it so much that he's created an action to apply it.
I use it for those reasons and especially when I want to make a local and color controlled change rather than a specific global adjustment.
I also use Lab channels often for creating masks.
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Scott Kelby, in The Photoshop Channels Book, says he uses Lab when he wants to add detail and vibrance to his images, especially landscapes. He adds that he uses it so much that he's created an action to apply it.
I use it for those reasons and especially when I want to make a local and color controlled change rather than a specific global adjustment.
I also use Lab channels often for creating masks.
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Yes, indeed Scott does - Chapter 5, "Creating Vibrant Color", and it is very easy. He acknowledges the source of the technique being Dan Margulis, and he does it on a duplicate image layer so he can adjust it or discard it as he wishes. This of course was published well before CR 4.x and Lightroom became available, where (I believe from using them) much of the same kind of effects can be achieved wihout having to implement the L*a*b conversion and without needing a duplicate image layer. In my PPE presentation I did show a "canyone-type" image where I compared steepening the *a* and *b* curves on the one hand versus using Vibrance in CR 4.1 on the other, and the difference between the two results was indistinguishable - I really lost track of which image was which. Now that is one image. Maybe after a great many such comparisons one could build a set of prototypical situations where one approach would be preferred to the other - but that already tells us how diversified the options have become for achieving similar objectives. While the L*a*b approach worked fine, nowadays, personally, I would prefer the up-stream approach whenever it does what I want.
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He acknowledges the source of the technique being Dan Margulis, and he does it on a duplicate image layer so he can adjust it or discard it as he wishes.
Gee, that's true; I believe he mentions Dan (in his acknowledgments) as being the "bottom line when it comes to color". (Sorry; but I sat quietly through most of this thread )
This of course was published well before CR 4.x and Lightroom became available, where (I believe from using them) much of the same kind of effects can be achieved wihout having to implement the L*a*b conversion and without needing a duplicate image layer.
Yes, and I use Vibrance fairly often--especially when I want to prepare images for the Web. When making prints, I am much more interested in subtleties, and concentrate on enhancing local areas for adjustment. This is the primary reason knowledge of Lab is important: even Andrew said there is a role for Lab in some processing. Vibrance does a good job: it does it globally, and it has fixed settings. Lab can be used to apply local adjustments, giving the user the option to control all aspects of the adjustment--whether color, degree of effect, or sharpness.
My underlying point, as you know Mark, is that if we are consistently herded away from understanding the effects of any technique Dan Margulis or anyone touts or even mentions, we will be the less for it.
On the other hand, and I rarely get the chance to mention it, pointing up the flaws or alternatives in such procedures is equally important. It's just that these points carry much less weight (indeed are often hidden altogether) when presented with obvious personal bias.
In my PPE presentation I did show a "canyone-type" image where I compared steepening the *a* and *b* curves on the one hand versus using Vibrance in CR 4.1 on the other, and the difference between the two results was indistinguishable - I really lost track of which image was which. Now that is one image. Maybe after a great many such comparisons one could build a set of prototypical situations where one approach would be preferred to the other - but that already tells us how diversified the options have become for achieving similar objectives. While the L*a*b approach worked fine, nowadays, personally, I would prefer the up-stream approach whenever it does what I want.
Well said, and happily noted, Mark. I completely agree.
after edit:
This of course was published well before CR 4.x and Lightroom became available, where (I believe from using them) much of the same kind of effects can be achieved wihout having to implement the L*a*b conversion and without needing a duplicate image layer.
After posting this I came upon some additional information about Kelby's workflow in which a poster said Kelby's new book Seven Points includes several chapters in which he uses Lab for his results. I only relay this so that those who haven't yet experimented with the Lab color space will know that it is not obsolete, though it may well be less necessary.
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When making prints, I am much more interested in subtleties, and concentrate on enhancing local areas for adjustment. This is the primary reason knowledge of Lab is important: .................. Vibrance does a good job: it does it globally, and it has fixed settings. Lab can be used to apply local adjustments, giving the user the option to control all aspects of the adjustment--whether color, degree of effect, or sharpness.
My underlying point, as you know Mark, is that if we are consistently herded away from understanding the effects of any technique Dan Margulis or anyone touts or even mentions, we will be the less for it.
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Gloria, forgetting all the names - Dan, Andrew, Scott, me, you, but just focusing on the tools themselves , let us recall that within CR4.x /LR, one is not confined to global adjustments of Saturation with the Vibrance tool (which itself is less global than it may appear) or the Saturation control, but there is also the HSL tab with eight colour groups each of which is amenable to three sets of controls: saturation, hue and luminance. The Adobe folks moved off the conventional RGBCMY grouping into a configuration which research and experimentation indicated to them would be more useful to photographers. This is innovative and I have read some positive feedback about it. I too find it works well. So with these added 24 controls, CR/LR is capable of much more targeted work than used to be the case only within the past year.
I don't think there's any issue of being herded away from techniques - it's just a discussion about alternatives and their pros and cons. No-one needs to take anyone's word for it - at least I don't and neither do you - everyone with serious interest in it should be encouraged to experiment with the options and come to their own conclusions.
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Gloria, forgetting all the names - Dan, Andrew, Scott, me, you, but just focusing on the tools themselves
Once more, you bring us back to the issue at hand, Mark
within CR4.x /LR, one is not confined to global adjustments of Saturation with the Vibrance tool (which itself is less global than it may appear) or the Saturation control, but there is also the HSL tab with eight colour groups each of which is amenable to three sets of controls: saturation, hue and luminance. The Adobe folks moved off the conventional RGBCMY grouping into a configuration which research and experimentation indicated to them would be more useful to photographers.
In my experience with these controls, they are wonderful and innovative and highly useful. The downside is that they can't be limited beyond their predetermined effects. By which I mean, for example, if you choose a color slider to work on, all of that color in your image will be effected. Much of the time, I want this. When I don't, I need to tweak in PS, and that happens a lot. I need other techniques at that point, and Lab offers much in that regard.
I am not saying that those sliders are not easy to use and highly effective, I'm just saying when they aren't giving me the result I want, where I want it, I need to turn to other techniques. And those other techniques are much harder to learn and understand, but the results enable me to make the subtle but extremely important changes to create an image I intend to print and hang.
I don't think there's any issue of being herded away from techniques - it's just a discussion about alternatives and their pros and cons. No-one needs to take anyone's word for it - at least I don't and neither do you - everyone with serious interest in it should be encouraged to experiment with the options and come to their own conclusions.
I don't think it's that simple, Mark. But it should be.
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Gloria, yes, basically what we don't have in CR/LR are conventional channel ops, blend modes, layer styles, masking, overlays, etc. And for sure, when one needs those tools it is necessary to work in PS. I don't think anyone suggests that CR/LR are replacements for PS. They were never meant in that way - rather they are complementary and will most likely remain so for quite a while regardless of the progress to come in raw conversion technology. What's happening, and I see this continuing, is that as programs such as CR/LR keep advancing and adding capability, they will make it incrementally less necessary to deploy advanced techniques in PS.
I see at the final statements in both of our previous posts there is the word "should". Well, what to say, "should" is "should", "eh"?
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was wondering if, when and why anyone employs LAB color in their workflow? I applied some of the methods to some of my landscape photos and was very impressed with the outcome.
I often use Lab, always for a single reason. This reason may be irrelevant for other users.
I often "enrich" the images with pseudo-HDR, i.e. developing two TIFF versions from the same raw file. I do this almost always for the sake of the sky.
This way I end up with at least two layers: the sky and the everything else. However, the tonality of the sky is often "wrong", i.e. not what I want in that setting. In other cases the tonality is good, but I am still experimenting with different lightnesses.
Changing the luminousity in RGB changes the color as well (there is no color integrity). Changing the color is a recipe for frustration. Therefor I switch to Lab space, adjust the lightness and color of the sky and convert it back to sRGB. I do this usually in an own document, for I don't want to convert the entire image back and forth with the associated losses.
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I often use Lab, always for a single reason. This reason may be irrelevant for other users.
I often "enrich" the images with pseudo-HDR, i.e. developing two TIFF versions from the same raw file. I do this almost always for the sake of the sky.
This way I end up with at least two layers: the sky and the everything else. However, the tonality of the sky is often "wrong", i.e. not what I want in that setting. In other cases the tonality is good, but I am still experimenting with different lightnesses.
Changing the luminousity in RGB changes the color as well (there is no color integrity). Changing the color is a recipe for frustration. Therefor I switch to Lab space, adjust the lightness and color of the sky and convert it back to sRGB. I do this usually in an own document, for I don't want to convert the entire image back and forth with the associated losses.
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I don't understand the workflow here. How do you isolate the sky on one of the layers? What's the real purpose of the Lab conversion? Do you start your workflow from a raw file? If so you can create two versions, one having the sky the way you like it, the other everything else the way you like it, render each into Photoshop and blend them using a mask perhaps with a gradient, without converting to Lab. You can change the luminosity of a layer without affecting its colour by clipping a Curves Adjustsment layer to it in Luminosity blend mode. Have you compared these options with the Lab approach? I think compared with trips to Lab these options may result in more non-destructive editing flexibility and smaller file size. But I emphasize this is a tentative suggestion because your workflow isn't entirely clear (to me).
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How do you isolate the sky on one of the layers?
This is the most difficult part, but it has no relevance in this question. It is sometimes painstaking, combining several methods, though there are cases, when it is quite simple.
What's the real purpose of the Lab conversion?
To be able to adjust the color and the lightness independently of each other. In RGB mode if you adjust the lightness, the color too changes.
Do you start your workflow from a raw file? If so you can create two versions, one having the sky the way you like it, the other everything else the way you like it, render each into Photoshop and blend them using a mask perhaps with a gradient, without converting to Lab
As I posted it, this is exactly what I am doing. However, it is difficult to judge the "ideal" lightness and tonality of the sky, while one does not see the other areas. Usually the sky is too bright with the "normal" lightness of the rest. When I reduce the lightness, the sky gets darker, usually more blue, but the rest becomes worthless, one does not see them "side by side".
Plus, color adjustment in ACR is by far not as clear as in Lab. In fact, it can be disastrous.
You can change the luminosity of a layer without affecting its colour by clipping a Curves Adjustsment layer to it in Luminosity blend mode
Yes, you can. That's "poor man's choise".
I think compared with trips to Lab these options may result in more non-destructive editing flexibility and smaller file size
There is nothing destructive in this setting (I don't lose any colors in the sky, at least I have never noticed that).
The file size has nothing to do with the subject, as I convert the sky back in RGB and insert it in the original image in most cases.
I did not want to elaborate on this, because it really depends on the actual circumstances, but sometimes I keep everything in Lab (I archive the file this way), and I convert it in RGB only when creating a specific version for Web or for printing.
Anyway, the file size is not a consideration. My files are usually between 100 and 800 megabytes, a few more or less megabytes don't make any difference.
Finally, a note: the selective color adjustments of PS CS3 are really appealling at first sight, but they can be devastating. They are no contest for Lab (I do use this feature often, but warily).
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Plus, color adjustment in ACR is by far not as clear as in Lab. In fact, it can be disastrous.
You need more practice <g>. In the right hands, the ACR adjustments can be a much finer controlled tool.
Yes, you can. That's "poor man's choise".
What makes it poor?
There is nothing destructive in this setting (I don't lose any colors in the sky, at least I have never noticed that).
It is destructive no way around it using Lab. At least do it in 16-bit.
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This is the most difficult part, but it has no relevance in this question. It is sometimes painstaking, combining several methods, though there are cases, when it is quite simple.
To be able to adjust the color and the lightness independently of each other. In RGB mode if you adjust the lightness, the color too changes.
As I posted it, this is exactly what I am doing. However, it is difficult to judge the "ideal" lightness and tonality of the sky, while one does not see the other areas. Usually the sky is too bright with the "normal" lightness of the rest. When I reduce the lightness, the sky gets darker, usually more blue, but the rest becomes worthless, one does not see them "side by side".
Plus, color adjustment in ACR is by far not as clear as in Lab. In fact, it can be disastrous.
Yes, you can. That's "poor man's choise".
There is nothing destructive in this setting (I don't lose any colors in the sky, at least I have never noticed that).
The file size has nothing to do with the subject, as I convert the sky back in RGB and insert it in the original image in most cases.
I did not want to elaborate on this, because it really depends on the actual circumstances, but sometimes I keep everything in Lab (I archive the file this way), and I convert it in RGB only when creating a specific version for Web or for printing.
Anyway, the file size is not a consideration. My files are usually between 100 and 800 megabytes, a few more or less megabytes don't make any difference.
Finally, a note: the selective color adjustments of PS CS3 are really appealling at first sight, but they can be devastating. They are no contest for Lab (I do use this feature often, but warily).
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Well, I have some news for you:
The way in which you capture the sky IS relevant to this discussion, because you can often do it using the colour groups in Camera raw and avoid all those difficult procedures you allude to above.
You are wrong about not being able to envision the final results by doing a luminosity blend of two separately developed raw captures. This is a very well-known technique which many photographers employ frequently and successfully. You do not need perfection at the raw development stage. All you need is two images that replicatre approximately the two luminosity scales you want in the final result, bring them into PS, layer them, layer mask them, at which point you see the whole thing together, give each its own clipped Curves Adjustment layer, and you are off to the races.
You are wrong about a Curve in RGB Luminosity Blenad Mode being a poor man's choice relative to using the L curve in L*a*b - in fact it is the other way around. You won't find this in Dan Margulis' Canyon Conundrum book, but the factual conundrum is that the L channel in Lab mode has only fair chroma consistency when shifting the L Curve while holding the *a* and the *b* constant. I've tried both and couldn't tell the difference - LaCie 321 display and Epson 4800 printer. So no - if I want *relatively* pure luminosity adjustments, AND colour adjustments, and I want to keep them separated, I stay in RGB and use two Curves Adjustment Layers - one for luminosity and the other for colour. One often sees this recommended as "best practice".
Selective Color Adjustment Layers are only devastating in the hands of people who devastate images with them. They are not if you use them properly. They are far more intuitive and manageable than manipulating the *a* and *b* curves of L*a*b. Of course they are different tools and may therefore be used to achieve different effects. One shouldn't pre-suppose they are necessarily substitutes. "Selective Color" is one of the more unsung heros in the Photoshop arsenal. Very interesting and useful things can be done with it.
As for file sizes - I agree with you - I work on files in the 100~300 range, typically, and a few MBs more or less is perhaps no big deal, but if you can deploy techniques that consistently economize on file saize without compromising image quality, all those little bits add-up to save storage and make saving, printing and retrieval just that bit more efficient.
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I hesitate to enter this one , not having yet read The Canyon Conundrum, so I will just make a couple of comments from experience. I avoid moving to and from L*a*b, partly because of losses (even in 16 bit) and partly because of some distortions in the translation process. I do use it in a duplicate image , taking the L information and placing it as a Luminosity blended layer in the original image layer stack. The purpose of this is to alter the luminosity rendering to something more approximating human brightness perception. This move is used in combination with other luminosity and colour edits.
The use of two curves layers, one for colour (HSL) and and one for tonal control , blended accordingly , is mandatory if you want any independant control of colour and tone.
I guess the book in question does this with the *a and *b channels . In the brief time I have played with them , this adjustment seems very touchy, and so far makes no sense in jumping out of RGB.
There still remains a problem with the RGB dual blending approach, which is an inability of the Luminosity and Color blending modes to work at sufficient levels of accuracy for exacting applications. That is , the strategy definitely helps, but color still drifts when tone is changed and vv. even on fixed points. I suspect this is similar for L*a*b space, bur have not checked it out.
There is a lot on this at www.freegamma.com which proposes, as a solution, the program (actually a very complex PS droplet) Lobster.
This was mentioned in another thread some time ago. At that time Lobster was only available for Mac, but it now seem a Win version is available.
Lobster creates large files but solves the problem . I have no interest in the product apart from knowing one of the developers and using it when appropriate. It works.
HTH
I'm going off to play with Selective Color!
Brian
www.pharoseditions.com.au
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..............
There still remains a problem with the RGB dual blending approach, which is an inability of the Luminosity and Color blending modes to work at sufficient levels of accuracy for exacting applications. That is , the strategy definitely helps, but color still drifts when tone is changed and vv. even on fixed points. I suspect this is similar for L*a*b space, bur have not checked it out.
There is a lot on this at www.freegamma.com which proposes, as a solution, the program (actually a very complex PS droplet) Lobster.
This was mentioned in another thread some time ago. At that time Lobster was only available for Mac, but it now seem a Win version is available.
Lobster creates large files but solves the problem . ...............
Brian
www.pharoseditions.com.au
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Brian,
Not having gone to "freegamma.com yet, which I shall, meanwhile could you elaborate a bit what you have in mind by "sufficient levels of accuracy" and relative to what kind of exacting applications? Also, do you understand how Lobster solves whatever this problem may be - I intend to visit their site too - last time I went there, it was Mac only which ruled me out so I lost interest.
Cheers,
Mark
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...but color still drifts when tone is changed...
Are you sure this is the case in PS? I remember Guillermo did some tests in Mark's 'Your Curves' thread in which he found that hue was preserved exactly in PS Luminosity blending mode, though saturation changed. Thus was not the case in CR, or of course PS normal blending mode. Guillermo's test (http://luminous-landscape.com/forum/index.php?showtopic=18413&st=20) --posts #28 and #39
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Are you sure this is the case in PS? I remember Guillermo did some tests in Mark's 'Your Curves' thread in which he found that hue was preserved exactly in PS Luminosity blending mode, though saturation changed. Thus was not the case in CR, or of course PS normal blending mode. Guillermo's test (http://luminous-landscape.com/forum/index.php?showtopic=18413&st=20) --posts #28 and #39
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Gloria, hue is preserved in CR, but not saturation.
Mark
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Gloria, hue is preserved in CR, but not saturation.
I was looking at Guillermo's results on that one, Mark. I certainly came away with the understanding that according to Guillermo's tests, hue was not exactly preserved (though it was close) in an CR curve adjustment:
Guillermo: ACR curves don't preserve Hue, and in addition to this don't work exactly as a PS Normal blending mode RGB curve. Only PS Luminance blending mode seems to preserve Hue, producing however an apparent saturation loss (or at least a feeling that this happens).
Regarding LR, the new one:
- Seems to preserve Hue much better than PS Normal, but still modifies Hue.
-Increases saturation nearly the same as PS Normal.
Sorry, I didn't realize he recapped his results on the final page of the Your Curves thread, but these are his results. Have you found/heard something to the contrary? Or do you figure the changes are too close to count?
Post # 188 (http://luminous-landscape.com/forum/index.php?showtopic=18413&st=180)
Gloria
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You need more practice. <g> In the right hands, the ACR adjustments can be a much finer controlled tool
LOL, that's good.
Pls make following experiment:
1. Create a graduated block in 16-bit Lab mode, with fixed color, for example a=30, b=60. Not gray and not an RGB primary. The graduation should run from L=100 to L=50 (for example).
2. Make a copy of it and convert it in RGB.
3. Apply some luminosity change to the Lab version, like brightness -50, whatever.
4. Do the same on the RGB version with blending mode luminosity, and merge the layers.
5. Convert the modified RGB in Lab, and compared them. If you convert the modified Lab in RGB, you see the difference, but in Lab mode you can quantify it.
It is destructive no way around it using Lab
No, it is not. More accurately, it depends. Check out the gamuts of the RGB spaces: they are very good just in the blue corner.
At least do it in 16-bit
Of course I do - not from the color space conversions, but starting with ACR, up to the point of generating the presentation version. That is part of the reasons my files are hundreds of megabytes large.
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Pls make following experiment:
1. Create a graduated block in 16-bit Lab mode, with fixed color, for example a=30, b=60. Not gray and not an RGB primary. The graduation should run from L=100 to L=50 (for example).
2. Make a copy of it and convert it in RGB.
3. Apply some luminosity change to the Lab version, like brightness -50, whatever.
4. Do the same on the RGB version with blending mode luminosity, and merge the layers.
5. Convert the modified RGB in Lab, and compared them. If you convert the modified Lab in RGB, you see the difference, but in Lab mode you can quantify it.
I have absolutely no idea what you're trying to propose here and the instructions are anything but clear. What layers am I blending on the RGB copy? Do you mean fade/Luminosity? And what does "but in Lab mode, you can quantify it" mean?
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Check out the gamuts of the RGB spaces: they are very good just in the blue corner.
Oh, I also don't understand what this sentence means.
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Well, I have some news for you:
The way in which you capture the sky IS relevant to this discussion, because you can often do it using the colour groups in Camera raw and avoid all those difficult procedures you allude to above.
Well, I have some news for you: real life is more complicated. I usually use a combination of several methods. It depends on the actual images and on the personal level of acceptance, how laborous the process is.
You are wrong about not being able to envision the final results by doing a luminosity blend of two separately developed raw captures. This is a very well-known technique which many photographers employ frequently and successfully
You did not understand what I was writing. Of course you can compare them, but not in ACR. The above way may be right with your workflow, but that is not how I am creating panoramas.
All you need is two images that replicatre approximately the two luminosity scales you want in the final result, bring them into PS, layer them, layer mask them, at which point you see the whole thing together, give each its own clipped Curves Adjustment layer, and you are off to the races
This is exactly what I do and what I described above. The difference is only that I often convert the sky in Lab for adjustment.
You are wrong about a Curve in RGB Luminosity Blenad Mode being a poor man's choice relative to using the L curve in L*a*b - in fact it is the other way around
You too could profit from the experiment I describe in my previous post.
Of course they are different tools and may therefore be used to achieve different effects. One shouldn't pre-suppose they are necessarily substitutes
You got at least this one right. I am using selective color adjustments in PS (the adjustments in ACR are of very limited use). However, when adjusting the sky, I prefer Lab. I do agree, that color adjustment in Lab may be a pain.
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I was looking at Guillermo's results on that one, Mark. I certainly came away with the understanding that according to Guillermo's tests, hue was not exactly preserved (though it was close) in an CR curve adjustment:
Guillermo:
Sorry, I didn't realize he recapped his results on the final page of the Your Curves thread, but these are his results. Have you found/heard something to the contrary? Or do you figure the changes are too close to count?
Post # 188 (http://luminous-landscape.com/forum/index.php?showtopic=18413&st=180)
Gloria
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Gloria - ya - what's to the contrary is that the writer of the code says what I reported. As well, most of my test results bear him out. I did have one outlier which no-one who saw it could figure out. But otherwise it behaved as advertised. I never really understood how Guillermo got the hue shifts he reported - would have taken a lot of back-and-forth to get to the bottom of that and I'm not sure I would have been the peson able to decipher exactly how he got what he got, so I didn't push it.
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Gloria - ya - what's to the contrary is that the writer of the code says what I reported. As well, most of my test results bear him out. I did have one outlier which no-one who saw it could figure out. But otherwise it behaved as advertised. I never really understood how Guillermo got the hue shifts he reported - would have taken a lot of back-and-forth to get to the bottom of that and I'm not sure I would have been the peson able to decipher exactly how he got what he got, so I didn't push it.
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Thanks Mark. This will go back on my sometimes, probably, most of the time, somewhat list of interesting PS effects.
Gloria
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Well, I have some news for you: real life is more complicated. I usually use a combination of several methods. It depends on the actual images and on the personal level of acceptance, how laborous the process is.
You did not understand what I was writing. Of course you can compare them, but not in ACR. The above way may be right with your workflow, but that is not how I am creating panoramas.
This is exactly what I do and what I described above. The difference is only that I often convert the sky in Lab for adjustment.
You too could profit from the experiment I describe in my previous post.
You got at least this one right. I am using selective color adjustments in PS (the adjustments in ACR are of very limited use). However, when adjusting the sky, I prefer Lab. I do agree, that color adjustment in Lab may be a pain.
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Grerat, we've had news for eachother - keeps discussion lively .
I agree - no one method of selecting a sky works all the time. I wasn't saying that. Just in my experience, more often than not working the blues in those HSL tabs of CR4.x can really go a long way to getting a very good end result. To that extent, it alleviates the workload and gymnastics in PS.
And I agree - one cannot compare image adjustments between two versions simultaneously in CR; I just don't think that's a big limitation, but as they say YMMV.
For some time I also reverted to Lab for certain kinds of enhancements and found it very effective. But it is a tricky space to work with, and I just find that new tools and techniques have substantially reduced its relative attractiveness - but I'd be the last one to say it's not useful some of the time. There will always be those situations............
In the procedure you recommended to Andrew, I could understand where you were going until item #5, and there you lost me. So I don't get the point of it. Something isn't explained quite right there - at least to my understanding. I'm assuming that whether we are talking panoramas or more usual photographs the issue at question here is not related to that, but rather to the relative effects of making luminosity tweals in RGB Luminosity versus LAB Luminosity - right?
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Thanks Mark. This will go back on my sometimes, probably, most of the time, somewhat list of interesting PS effects.
Gloria
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Yup - at this point that's where it's at with me too.
One can go on and on experimenting, but you know, with a properly profiled display and a good printer you can see where these curve adjustments are heading and there's umpteen ways at various stages of the creative process for dealing with unwanted side-effects, so it just isn't that big a deal - but that's me. I think once one gets into - say- advertising work, whatever one does the numbers often need to be spot on - but even in those cases based on what we've been told about the behaviour of those curves, it's not at all clear that L*a*b is necessarily the most efficient or effective route to colour accuracy.
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I'm assuming that whether we are talking panoramas or more usual photographs the issue at question here is not related to that, but rather to the relative effects of making luminosity tweals in RGB Luminosity versus LAB Luminosity - right?
Exactly. The point is, that color integrity is not maintained (can not be maintained) in RGB. This means, that if you change the luminosity, the color changes as well, except if all non-zero components have the same value. Grey, red, green, blue, yellow, cyan and magenta remain grey, red, etc.
There is no such problem in Lab. The other side of this is, that when converted back to RGB, the change of luminosity becomes non-linear. I don't find that a problem, particularly because any contrast enhancement changes the luminance proportions anyway, so the integrity of luminosity is a moot issue. Although this change does effect the contrast to some degree, I have never seen this as an issue, but I can imagine applications, where this might pose a problem. However, color integrity is IMO more often an issue.
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Brian,
Not having gone to "freegamma.com yet, which I shall, meanwhile could you elaborate a bit what you have in mind by "sufficient levels of accuracy" and relative to what kind of exacting applications? Also, do you understand how Lobster solves whatever this problem may be - I intend to visit their site too - last time I went there, it was Mac only which ruled me out so I lost interest.
Cheers,
Mark
About 3.5 years ago I had a job to reproduce some hundreds of pieces of artwork. These consisted of oil, acrylic, pencil, crayons and stuck on bits of siver and gold metal. I learned a lot about colour inconstancy as light sources changed (on Epson K2 inkset then) and the need to edit custom profiles. Even after sorting out aforementioned hassles I would adjust saturation and tone changed and VV. Blending modes helped a lot but when it came to getting those colours perceptually accurate , I was still chasing my tail. When Les Walkling showed me Lobster (no , I am not a born again salesman) I could not believe how you could crank curves up and down and only get the shift you wanted. The screen images remained "clean". At that time I tested the numbers and was getting the small (and in some cases large) shifts that Free Gamma claimed. The end of that story is I finally got those colours right with a new workflow that incorpoated the software. I may have told this story a long time ago , but the audience is larger now and the software is dual platform.
When required ,I use the Lobster approach. I don't use it all the time, as you have to flatten layers , which I prefer not to do , and the file size is large.
I was on CS at the time and have recently moved to CS3 .I have not re-done the tests, but will do so when I get a break. The tests, as suggested in the Lobster manuals, take a while and some concentration.
Cheers,
Brian
www.pharoseditions.com.au
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The point is, that color integrity is not maintained (can not be maintained) in RGB. This means, that if you change the luminosity, the color changes as well...
But if hue is maintained in ACR, wouldn't it be easier and just as effective for you to make adjustments there, or with the HSB sliders therein? That is, if your only reason to move to Lab is to maintain color integrity?. (Noise, haloes, and global application being other considerations in select images)
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Exactly. The point is, that color integrity is not maintained (can not be maintained) in RGB. This means, that if you change the luminosity, the color changes as well, except if all non-zero components have the same value. Grey, red, green, blue, yellow, cyan and magenta remain grey, red, etc.
There is no such problem in Lab. The other side of this is, that when converted back to RGB, the change of luminosity becomes non-linear. I don't find that a problem, particularly because any contrast enhancement changes the luminance proportions anyway, so the integrity of luminosity is a moot issue. Although this change does effect the contrast to some degree, I have never seen this as an issue, but I can imagine applications, where this might pose a problem. However, color integrity is IMO more often an issue.
[a href=\"index.php?act=findpost&pid=155413\"][{POST_SNAPBACK}][/a]
Hi Pano,
You are correct that shifting the RGB composite Curve in Normal Mode does not preserve "colours"'; more accurately it definitely does not preserve saturation - it was designed that way on purpose - and there can be slight hue shifts as well. I have tested this issue of hue shifts at least several times over the past few years when it surfaced in discussions on this website and others in various contexts. My results have always indicated that these hue shifts tend to be very slight, if any. This I found by retaining the RGB working space, but looking at the measurements "before" and "after" in RGB, L*a*b and HSB measurement systems. By the way, I have two articles on this website dealing in part with this subject (Do Curves Throw You a Curve, and the sequel).
Now, as to the merits of L*a*b for preserving "colour" - the FACT is - as I mentioned in a previous post here, "L" has only fair chroma consistency, so if you are after "colour integrity", the "L" channel in theory is not where you will be certain to obtain it. I completely agree with a point made above by Jeff Schewe that shifting to L*a*b for this purpose isn't worthwhile compared with using the RGB Curve in Luminosity Blend mode. On a print of a real-world photograph, you really do need to search long and hard for any significant difference of results between shifting the "L" Curve or shifting the RGB Curve in Luminosity Mode. And with a bit of skill you can often simulate an L*a*b result in Camera Raw so darn close you lose track of which image is which. Of course this would vary from image to image, but the basic point is there.
So going back to Tad's original question in Post #1 above, I think Dan Margulis demonstrated much interesting and useful stuff in the L*a*b book, but I personally find that for the overwhelming majority of images I work-up (roughly 200 per month) there's been no compelling need or advantage of converting to L*a*b, especially since Lightroom and CS3. But if incorporating L*a*b in a regular workflow suits your needs best, then of course that's fine too - what's so nice about Photoshop - multiple paths to similar destinations.
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Brian,
Not having gone to "freegamma.com yet, which I shall, meanwhile could you elaborate a bit what you have in mind by "sufficient levels of accuracy" and relative to what kind of exacting applications? Also, do you understand how Lobster solves whatever this problem may be - I intend to visit their site too - last time I went there, it was Mac only which ruled me out so I lost interest.
Cheers,
Mark
About 3.5 years ago I had a job to reproduce some hundreds of pieces of artwork. These consisted of oil, acrylic, pencil, crayons and stuck on bits of siver and gold metal. I learned a lot about colour inconstancy as light sources changed (on Epson K2 inkset then) and the need to edit custom profiles. Even after sorting out aforementioned hassles I would adjust saturation and tone changed and VV. Blending modes helped a lot but when it came to getting those colours perceptually accurate , I was still chasing my tail. When Les Walkling showed me Lobster (no , I am not a born again salesman) I could not believe how you could crank curves up and down and only get the shift you wanted. The screen images remained "clean". At that time I tested the numbers and was getting the small (and in some cases large) shifts that Free Gamma claimed. The end of that story is I finally got those colours right with a new workflow that incorpoated the software. I may have told this story a long time ago , but the audience is larger now and the software is dual platform.
When required ,I use the Lobster approach. I don't use it all the time, as you have to flatten layers , which I prefer not to do , and the file size is large.
I was on CS at the time and have recently moved to CS3 .I have not re-done the tests, but will do so when I get a break. The tests, as suggested in the Lobster manuals, take a while and some concentration.
Cheers,
Brian
www.pharoseditions.com.au
[a href=\"index.php?act=findpost&pid=155416\"][{POST_SNAPBACK}][/a]
Thanks for that explanation Brian. I see what kind of images you are talking about - that is indeed very challenging in two respects - getting the artwork to look like it should, and reproducing metallic colours without metallic inks. I did now visit the Lobster website again (I had actually seen it some time ago before there was a WINXP edition). It looks enticing in some respects, but the flattening and file size issues I must say dampen my enthusiasm. It looks like the kind of application one would use when nothing else works properly - and he is careful to keep repeating one should use it on a duplicate of the image. Talking about nothing else working properly, periodically Curvemeister is mentioned as being a useful application for making Curves adjustments in multiple modes. Have you ever worked with that application (I haven't, yet)?
Now that you are on CS3, an interesting thing to try may be to revert to one of those challenging artwork images - a raw file - duplicate it, reset all the conversion adjustments to zero and linear retaining "As Shot" white balance, and reprocess the image as far as you can using all the available tools in CR 4.1+. Then render into PS and do the remainder there, without Lobster, as best you can, and compare the outcome with your Lobster results. If you have the time and interest to do this, I'd be very interested in your observations about the comparative outcomes.
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periodically Curvemeister is mentioned as being a useful application for making Curves adjustments in multiple modes. Have you ever worked with that application (I haven't, yet)?
I use Curvemeister a lot, and find it very effective in making adjustments to skies (an example we have been using). One can create a mask derived from any channel to isolate the sky if needed (usually making further blending unnecessary), and then use a curve from within any color mode to make adjustments. I am finding great benefit from using curves from the HSB color mode on the skies (Lab curves are also available), and these curves all work independently from each other, and info can be read on specific targets while adjustments are being made.
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Lobster seems like a great tool for those who want to edit luminosity and color separately. I would think that it is used at the front end of a workflow before other layers are generated. So why is flattening an issue?
The site provides no real image examples before and after applying Lobster, making it difficult to see what the effects are. Google and I find no user reviews. Perhaps it is only appreciated by a few, but not very popular.
I did now visit the Lobster website again (I had actually seen it some time ago before there was a WINXP edition). It looks enticing in some respects, but the flattening and file size issues I must say dampen my enthusiasm. It looks like the kind of application one would use when nothing else works properly - and he is careful to keep repeating one should use it on a duplicate of the image.
[a href=\"index.php?act=findpost&pid=155455\"][{POST_SNAPBACK}][/a]
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Lobster seems like a great tool for those who want to edit luminosity and color separately. I would think that it is used at the front end of a workflow before other layers are generated. So why is flattening an issue?
.......................
[a href=\"index.php?act=findpost&pid=155736\"][{POST_SNAPBACK}][/a]
You can always flatten the luminosity and colour adjustments into the Background layer, but then you lose the principal advantages of working with Adjustment Layers for amending these edits should you wish to re-purpose the file or make changes that you later decide are necessary. The only changes I bake into the file after leaving Camera Raw are crops, perspective adjustments, noise reduction and capture sharpening. The rest is on layers, and as much as allowed on Adjustment Layers.
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You are correct that shifting the RGB composite Curve in Normal Mode does not preserve "colours"'; more accurately it definitely does not preserve saturation - it was designed that way on purpose
Only a small technical remark (otherwise I think the subject has been discussed more than enough): not maintaining the color integrity is not per design, it is the nature of RGB, it could not be otherwise.
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Only a small technical remark (otherwise I think the subject has been discussed more than enough): not maintaining the color integrity is not per design, it is the nature of RGB, it could not be otherwise.
[a href=\"index.php?act=findpost&pid=155862\"][{POST_SNAPBACK}][/a]
Actually no, if you read Mark's article here, you'll that it is indeed by design.
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I had been using LAB quite extensively until I purchased CS3. I've found that I am able to utilize the tools in ACR now to achieve similar effects (tone curve, vibrance, clarity, and HSL tabs) and no longer make the trip to LAB as often. There are still a few areas where I still find it useful (creating layer masks and new L channels from a single RGB channel) but it is no longer the integral part of my workflow that it once was.
The Canyon Conundrum still occupies a place of honor in my bathroom, but I have just purchased Real World ACR and am eagerly awaiting its arrival.
P.S. Thank you to the forum members who have participated in this and other discussions on LAB... you have helped me gain a much better understanding of its proponents, merits and issues.
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again
what you have to understand is that when you view an image its in sRGB ( or if you have a CRT or an LCD or PLASMA) maybe in ABOBE1972
your picture is en coded in a space you cant see!
not the editing space!
don't do visual editing on as RGB monitor
the monitor is and is struggling to be to "negative'
its no where near.
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I've tried out editing in Lab space white balancing the blue cast out of sunset lit limestone rock while not affecting the blue in other elements in the scene such as flowers. Far more intuitive and smoother than using selective color in RGB.
However, one issue I found from my own experience working in this space is that it tended to skew my color perception through the adaptive process when I took too long editing in this space. With each edit along the a/b curves tended to ever so slightly change the hue of nearby colors on the color wheel within the image without me noticing.
When I took a break to allow my eyes to adjust a bit, something just looked off about the image looking at it with a fresh eye.
I've seen results similar to this effect on the web in the past of images edited in this space most seeming to have a very neutral carbon black undercolor sheen starting from shadows tapering off into the mids. It's kind of like the desaturated effect that comes about applying a blur on color blend layer to get rid of purple fringing. An overall inconsistancy in hue and saturation levels permiates through different areas of the image giving it an odd look.
And the Dan inspired tutorials I've come across on the web tend to be quite long winded and too much work for what little results that were gained.
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I've tried out editing in Lab space white balancing the blue cast out of sunset lit limestone rock while not affecting the blue in other elements in the scene such as flowers. Far more intuitive and smoother than using selective color in RGB.
For something like that, I'd do two developments of the RAW file, the first white balanced for the limestone, the second white balanced for the rest of the scene, layer one over the other, and paint the layer mask to blend to taste. Much easier than selective color tweaks that generally have unexpected consequences in unrelated areas of the image.
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Jonathan,
This was a scan from a Kodak UC 400 negative of as scene that seemed to have a much wider gamut than my Epson 4870 and negative could deliver.
The fine tweaks on the 16bit tiffs I could do in Lab were unbelievable. It was like editing the color lookup table of the image itself which can get really hairy if you don't know what you're doing. And apparantly I didn't.
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Here's the image. The more I go back to it the more I have say to myself what the hell was I thinking?
You'll see from the top Epson Auto Exposure version what I had to deal with compared to the results of Lab at the bottom which looks more to what I imagined it from memory. The flowers were that exact color and limestone was warmish because of how low the sun was set. It still looks off. It doesn't look how I remember the scene.
The flowers were intense and eyepopping and I couldn't get that look editing in RGB, though I tried, from what the Epson and the Kodak negative delivered.[attachment=4135:attachment]
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I've tried out editing in Lab space white balancing the blue cast out of sunset lit limestone rock while not affecting the blue in other elements in the scene such as flowers. Far more intuitive and smoother than using selective color in RGB.
.............................
An overall inconsistancy in hue and saturation levels permiates through different areas of the image giving it an odd look.
...........................
[a href=\"index.php?act=findpost&pid=158216\"][{POST_SNAPBACK}][/a]
I'm having some trouble understanding what's happening here. If limestone is lit by the setting sun, one would not normally expect it to have a blue cast. If anything, the stone should be rather yellow/orange. This raises a question about the quality of colour balance in the scan itself. I've scanned tons of colour negs (in fact written two articles about it on this website) and there is no question in my mind that if you don't get the colour balance nearly right at the scan stage, it is difficult to rescue it in Photoshop, regardless of the colour space used.
Anyhow, returning to the blue in the rocks - you want to neutralize that without also neutralizing the blue in the flowers, but then toward the end of the story you report getting inconsistency in hue and saturation through different areas of the image. That comment raises a question about whether you achieved your objective of using Lab curves to eliminate blue from the rock while preserving blue in the flowers. If you succeeded in doing so without using a layer mask, I'd be curious to know how you shaped the *b* curve to achieve it. One possible approach I could see to this challenge is that if the shades of blue between the flowers and the limestone are different enough, you could, in Layer Styles", isolate the impact of the curve movement to the blue tone on the rock by adjusting the "Blend If" sliders for the *b* curve. Anyhow, however you did it - do tell.
I agree with you that playing with *a* and *b* curves in Lab puts colours on steroids and control is *not easy*, especially when it comes to using them for rebalancing colour. They are much easier to use for saturating colour while retaining the same colour balance, but rebalancing in a way that gives you the "correct" result accross the tonal range for both the *a* and *b* axes is very challenging.
Now, reverting to Jonathan's suggestion made assuming you were adjusting a digital capture, his idea can also be applied to a scanned negative, either by producing two scans with different colour balance settings and layering them, assuming the scanner is dead-on consistent pixelm by pixel from one scan to the next, or by creating a duplicated image layer which you would mask in one way or another, and clip Curves in RGB space to each of the background and the duplicate for the colour balancing, isolated to the effect intended for each layer. I suggest this, because Selective Color, which you mention, is not the first place I would go for altering the colour balance of an image. I would start with the individual R, G, and B Curves.
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Here's the image. The more I go back to it the more I have say to myself what the hell was I thinking?
You'll see from the top Epson Auto Exposure version what I had to deal with compared to the results of Lab at the bottom which looks more to what I imagined it from memory. The flowers were that exact color and limestone was warmish because of how low the sun was set. It still looks off. It doesn't look how I remember the scene.
The flowers were intense and eyepopping and I couldn't get that look editing in RGB, though I tried, from what the Epson and the Kodak negative delivered
[a href=\"index.php?act=findpost&pid=158247\"][{POST_SNAPBACK}][/a]
Sorry - while you were posting I was writing and I saw this after I posted! I see we agree the Limestone should have been warmish - only makes sense, doesn't it ; then you say the flowers are now "exact", but the scene doesn't look like how you remembered it. It's hard to discuss without knowing more information. It looks to me as if your Lab edit was quite successful, and I see that there is a substantial tonal difference in the blues between the flowers and the rock which would facilitate the use of Lab. In this case, Lab has allowed you to isolate the blues. It looks to me as if you didn't touch the *a* curve, because the reds and greens look relatively unchanged except for a slight increase in yellow, which comes from adjusting the *b* curve. It also looks as if you desaturated the blue somewhat, because the detail in the flowers has improved. It would be good to hear more about how you implemented the Lab edits, and could you explain in what ways the scene still does not look right to you?
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Now, reverting to Jonathan's suggestion made assuming you were adjusting a digital capture, his idea can also be applied to a scanned negative, either by producing two scans with different colour balance settings and layering them, assuming the scanner is dead-on consistent pixelm by pixel from one scan to the next, or by creating a duplicated image layer which you would mask in one way or another,
Can't you open non-RAW files in ACR in CS3, and do WB adjustments that way? If so, you could layer the same scan twice with different WB adjustments, and avoid the registration issues you get from layering multiple scans..
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MarkDS,
Just got your last post. I believe we crossed post.
I've posted a rough version of my Lab curve edits because I did this about a year ago and cleaned house and tossed them. I spent a great deal of time teaching myself how to fix an image like this in Lab-a tweakers paradise. It was my first and a real eye opener and a lot of fun as well.
What looks off about the image to me is a sense of lack of realism mainly due to inconsistant hues. I was shooting for the "you are their" feel which digicams seem do with little effort. I was trying to make a bad scan look as real as what I saw as much as possible.
To be a little more picky I don't like the cyanish green hot spots in the shadows of the flower's leaves compared to the orangish green in the brightly lit portion which I do like.
Getting the limestone to look the right warmish hue as if lit by the sun while at the same time making the shadows texture look right didn't come off like I wanted. The shadows still look too blue. Also adaptation started kicking my butt WB-ing this limestone so the scene looked as if it was lit by an evenly colored lightsource. And I constantly had to zoom in on the area I was tweaking to tame these off hue hotspots that crop up and can't detect in a busy scene like this.
I like how it came out it just I didn't reach the level of realism I was shooting for.
In fact after the Lab edits I went back into Epson scan and tried to emulate the same Lab results shown here and got a lot closer than Epson Auto Exposure. However, it was like whittling Mount Rushmore at actual size, but I saved the edits and applied them to the rest of frames on the strip of negative and all the rest of the images just popped. It was as if the blue flower image acted as a calibration target. I barely had to do any edits on the rest of the images except for an occasional WB tweak. [attachment=4136:attachment]
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Can't you open non-RAW files in ACR in CS3, and do WB adjustments that way? If so, you could layer the same scan twice with different WB adjustments, and avoid the registration issues you get from layering multiple scans..
[a href=\"index.php?act=findpost&pid=158261\"][{POST_SNAPBACK}][/a]
Jonathan - yes indeed! EXCELLENT!
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MarkDS,
[attachment=4136:attachment]
[a href=\"index.php?act=findpost&pid=158268\"][{POST_SNAPBACK}][/a]
Thanks for creating that attachment. I see what you were doing. That kind of curving is really hard to control - I think you pulled it off well considering the challenge. Where it runs into trouble is what happens to various colours along the curve at the points you did NOT select. You're right - as you move off center, you migrate from grey to increasing saturation of some hue, that hue being represented by whatever balance of values between green/magenta or blue/yellow the curve happens to be at from point to point and along the continuum between the points. And because each pixel is usually a combination of values from each curve, as you tweak one you may find it necessary to go back and re-tweak the other. Except for very simple things, it can really be tedious and finicky. I like Jonathan's idea. Added to which, in Camera Raw you have the HSL tab with 24 additional levers - influencing the H, L, and S of 8 colour groups. Much more intuitive than Lab. It may not be as precisely targetable, but it also won't drive you crazy stretching it to the limits of what it can do properly before you need additional work in Photoshop, which by then should not be heavy-lifting.
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Agree MarkDS,
That was a rough curve. I actually did have to lock down the entire curve of both a/b channels with a series of closely spaced tweak points. And you're right it was a daunting procedure with rewards that paid off.
I tried using selective hue/saturation in RGB but it required a lot of -/+ clicking with the eyedropper for each color which ended up amplifying film grain and scanner noise with an increase in saturation for each color selected so much so that I had to keep going back and forth with the eyedropper tool selecting and deselecting. It was just too crude and inprecise way of editing.
Lab was smooth much like sculpting each color as long as you kept certain portions of the a/b curve adjusted in flattened sections where the next selection point for each new section would isolate a certain color like a surgeon's knife. This required zoomed view of course.
It wasn't a quick edit, but a long session of tweaks that allowed me to learn quite a bit about the advantages and limits of working in Lab. Most of the limitations were with my own eyes getting used to look of the tweaks.
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Not too sure if this has been posted previously, but it seems to be a similar technique to what you are trying to achieve with the above flower image.
http://www.largeformatphotography.info/for...ead.php?t=19014 (http://www.largeformatphotography.info/forum/showthread.php?t=19014)
I have set these up and saved them as presets, which can then be used in actions. The de saturation from this curve is still a bit strong, but then you can easily lower the opacity of the effect to suit.
.
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again
what you have to understand is that when you view an image its in sRGB ( or if you have a CRT or an LCD or PLASMA) maybe in ABOBE1972
your picture is en coded in a space you cant see!
not the editing space!
don't do visual editing on as RGB monitor
the monitor is and is struggling to be to "negative'
its no where near.
[a href=\"index.php?act=findpost&pid=158055\"][{POST_SNAPBACK}][/a]
Ah , so that's where I've been going wrong alll this time. I've been using a monitor to edit my images!
Damn, I must stop doing that and go back to a more Zen like way of editing. One where's there are no numbers or colour spaces.
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Lightbox,
Thanks for posting the link to that thread. I remember reading it when it was originally posted. Chris Jordan's tips were pretty close to what I ended up doing but at a much slower pace.
Did you happen to check his site out. Surprised to find out that's the very same Chris Jordan from the PBS and Colbert Report interviews I recently saw on TV.
My brush with fame.
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Did anybody check out this weeks photoshop tv? Scott kelby does a lab mode conversion and back but says it's not distructive? This thread suggests otherwise. Wayne
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Did anybody check out this weeks photoshop tv? Scott kelby does a lab mode conversion and back but says it's not distructive? This thread suggests otherwise. Wayne
[a href=\"index.php?act=findpost&pid=158885\"][{POST_SNAPBACK}][/a]
It is by no means agreed in the industry that Lab conversions are not *destructive*. With a web search and you will find the evidence. Most of the destruction is said to happen with the first conversion forth and back. Thereafter, it is suggested, successive conversions of the same image are much less incrementally destructive. The real question is to what extent does the destruction matter - how much difference can you see in a print between an image that has been in and out of Lab versus the same one that has not? I've tried it with some images a couple of years ago and frankly I couldn't detect which was which, BUT at the same time the impact of Lab conversion has been demonstrated. Again, a search through this discussion forum and elsewhere on the internet will reveal that this is hazardous territory for *blanket statements* - it's *shades of grey* - or shall we say - the *L* Channel
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Lightbox,
Thanks for posting the link to that thread. I remember reading it when it was originally posted. Chris Jordan's tips were pretty close to what I ended up doing but at a much slower pace.
Did you happen to check his site out. Surprised to find out that's the very same Chris Jordan from the PBS and Colbert Report interviews I recently saw on TV.
My brush with fame.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=158856\")
[a href=\"http://www.brucelindbloom.com/index.html?ColorCheckerRGB.html]Bruce Lindbloom[/url] has a demo with an 8 bit sRGB TIFF containing all possible colors. He converted it to Lab and found that only 13% of the colors were preserved, a substantial loss. In converting it back to sRGB, there was little further loss. With 16 bits there would be less of a loss, and 16 bits/channel is usually recommended for Lab.
Bruce's site does not allow direct links, so click on the Info tab and then go down the page to An RGB Image Containing All Possible Colors
I know Scott Kelby is a popular author. I bought his Photoshop CS2 Book for Digital Photographers and was not impressed. Rather than substance, he spends a lot of time covering flashy tricks for special effects that I would never use, and I seldom refer to his book. Martin Evening's book on the same subject is more to my liking, even though I do not do fashion photography.
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It is by no means agreed in the industry that Lab conversions are not *destructive*
[a href=\"index.php?act=findpost&pid=158901\"][{POST_SNAPBACK}][/a]
I don't know what Scott means by not destructive. If he means there's no data loss in the conversion, well that's clearly way off base. And the reference to Lindbloom's site is worth a visit for anyone wondering about this (someone send a link to Scott). Depending on the original color space, a nice number of levels get tossed away. I wouldn’t call that non destructive but I haven't seen the video in question nor know the context of the comment (visually destructive on screen? On some output device? After X number of further edits to the data? From 8-bit or 16-bit).
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Heres a link to the video (it only there till Monday) I just wondered if anybody had seen it and what they though. Wayne
link (http://www.photoshopusertv.com/)
By the way my comment wasn't ment to be critical of this thread, theres a wealth of expertise on this forum.
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Heres a link to the video (it only there till Monday) I just wondered if anybody had seen it and what they though. Wayne
link (http://www.photoshopusertv.com/)
[a href=\"index.php?act=findpost&pid=158932\"][{POST_SNAPBACK}][/a]
He's working in an 8-bit file (you can see this from the menu when he moves to Lab).
He says "It doesn't harm the image, Its a non destructive move..."
(Its at 5:40 within the video time line).
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He's working in an 8-bit file (you can see this from the menu when he moves to Lab).
He says "It doesn't harm the image, Its a non destructive move..."
(Its at 5:40 within the video time line).
[a href=\"index.php?act=findpost&pid=158945\"][{POST_SNAPBACK}][/a]
Sounds like Dan Margulis . Readers who looked at Bruce Lindbloom's analysis might also want to read his Margulis 16 bit challenge.
Bill
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He's working in an 8-bit file (you can see this from the menu when he moves to Lab).
He says "It doesn't harm the image, Its a non destructive move..."
(Its at 5:40 within the video time line).
[a href=\"index.php?act=findpost&pid=158945\"][{POST_SNAPBACK}][/a]
Andrew, is this for info purposes only or was there a point you intended to make abouti t?
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Sounds like Dan Margulis . Readers who looked at Bruce Lindbloom's analysis might also want to read his Margulis 16 bit challenge.
Bill
[a href=\"index.php?act=findpost&pid=158952\"][{POST_SNAPBACK}][/a]
Bill, I suspect that Scott is relying on Dan's position here, and perhaps his own observations of not seeing actual destruction moving files back and forth. I have not see from Dan Margulis any technical underpinning for his position on this matter. Perhaps it is also observation-based and if he didn't see destruction ipso facto there is no destruction - but we know from Bruce Lindbloom that is technically not correct.
I think Bruce Lindbloom demonstrates quite conclusively that the procedure is destructive, but as I said above, the real issue is how much destruction does one see on paper. This probably depends on how the image is purposed (small print, big print, paper type, sum total of edits etc.). As soon as I hear an edit is as potentially destructive as Bruce says it is, and if there are alternative less destructive ways of achieving the same results or close enough to, it's a no-brainer what one should (not) do.
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Andrew, is this for info purposes only or was there a point you intended to make abouti t?
[a href=\"index.php?act=findpost&pid=159013\"][{POST_SNAPBACK}][/a]
Just stating what I heard him say (and that I don't agree with).
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Just stating what I heard him say (and that I don't agree with).
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Ahah - the part in brackets was missing. Now *I hear you*.
Mark
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What's ironic, if that's the right term, is he is just making the Lab move to build a luminosity layer set to Screen (which makes the image in Lab look butt ugly). He could have duplicated the original image, converted to Lab, built the layer and shift dragged it onto the original RGB document. Is maybe one more step (well its about the same, you don't need to convert back to RGB). Its interesting to see the difference in color kick in when you convert from Lab back to RGB. If you try both techniques, the net results, especially based on what he's trying to do (paint in highlights) look about the same but with the duplicate technique, the original image doesn't have to be converted to Lab. All the stuff you paint into this image from the moved layer of course did undergo the Lab damage.
Then I found another potential issue. The original document I opened was in ColorMatch RGB, my working space is set for ProPhoto RGB. If you do the RGB to Lab and back, you end up (in this case) in ProPhoto RGB, not the original color space (ColorMatch RGB). That's not an issue when you just drag the Lab created layer back to the original RGB document.