We’ll work on both types of image in this chapter, starting with the elimination of color casts, which requires that we identify certain colors as being wrong from the outset. That can be difficult, unless we are favored by the presence of a known color, ordinarily something neutral—like snow or ice. Prepare to get cold. What Should Be Gray? The brooding Trinity monastery at Sergiev Posad, 50 miles from Moscow, is the Russian Orthodox Church’s equivalent of the Vatican. Reverend Sergius of Radonezh, who founded it in about 1340, played an important role in the consolidation of Russian power. Its historical importance is so immense that even the officially atheistic Bolshevik party named it a national landmark in 1920, and Stalin left it alone during his reign. Figure 4.1A also illustrates another impor- tant attribute of Russian history: winters that are notoriously hostile not just to invading armies, but to photographers. The image is so lacking in velocity that we have to think of LAB to liven matters up. If we use the same curves seen so far, however, the thing will become even more unbearably blue-green than it already is. All previous images have been easy because they were neutrally correct. Translated into lay English, that means that any areas that are supposed to be white, gray, or black are reasonably close to being just that. Retranslated for denizens of the LAB world, it means that these white areas measure reason- ably close to 0 A 0 B , which is how LAB defines neutrality. Figure 4.1A is so obviously messed up that it tempts us to start swinging before the pitch arrives. Proper pro- cedure is to take a few practice cuts, by measuring several points. This is particularly so when trying to assess neutrality; not every point we look at will be 0 A 0 B . Some may appear neutral but should properly be blue, others red, and so forth. But our suspicions will be confirmed if all the points in nominally gray areas turn out to have cold values—negative numbers in the A and B . That’s how it turns out. The lightest signif- icant point of the image is at the center of the snow nearest to us. I found this out by using the Image: Adjustments>Threshold command described in the box below. The average of several points in that light area is 79 L (10) A (5) B . The darkest significant point is under the bridge at left. Its average reading is 27 L (6) A (15) B . Interpretation: the endpoints should be more like 97 L and 6 L . So, the highlight is much too dark and the shadow much too light, and the image is very flat. Colorwise, the AB readings show a green cast in the highlights, since in the lightest area the magenta-green A channel is consid- erably more negative than the yellow-blue B . In the shadow, the cast is apparently more of a blue-green. It’s All About the Center Point 61 The White Point and the Threshold Before applying curves, we need to find the lightest and darkest points in the image. In Figure 4.1B, it’s clear not only that the snow is the lightest part, but also that its lightest area is in the center of the image. Yet when working with something as flat as Figure 4.1A, it’s often hard to pick out the light point. Many people like to find light and dark points by using the Image: Adjustments>Threshold command. This command changes the image into two colors only, black and white. A slider controls where the break takes place: everything lighter than the slider point becomes white and everything darker black. To find the darkest points of an image, therefore, open the Threshold command and, with Preview checked, move the slider to the left until almost all the image is white. If there’s any difficulty recalling what areas the dark parts now represent, click OK and then toggle back and forth between the original and the Thresholded image with Command–Z (Mac, Ctrl–Z PC ). Reverse the procedure to find the lightest part of the image. Chapter 4. It’s All About The Center Point Page 3 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. There must be some limited sunshine right above the tower in the center of the walls, be- cause the sky seems to be darker and bluer at the edges of the image than it is at the center. On the right side, it reads 67 L (10) A (10) B ; at center, it’s a lighter 75 L (8) A (9) B . Other objects of interest: the wall itself averages 65 L (7) A (7) B , and the golden dome of the 1770-vintage clock tower checks in at 55 L (6) A 4 B . Like Russian politics, these numbers can be hard to analyze, but the general trend is clear: the picture is too blue and too green simultaneously, but the green factor is worse. Is that what you would have guessed just by looking at Figure 4.1A? Moreover, not just the detail, but the color is hopelessly flat. Notice that all the mea- surements fall between (6) A and (10) A , a range of only five points. The B channel has a 15-point range, but that’s understandable in context. The sky must be at least slightly blue, because its B value is more negative than the snow’s. The golden dome logically has to have a big yellow component, so we expect a big positive B value. The A , on the other hand, should have a narrower range, because there’s nothing in the image that seems to have a particularly green or particularly magenta bias. But one way or another, both A and B need drastically increased contrast, and they both need to move toward warm colors, meaning toward more positive numbers. The trick is figuring out how far to go. This opponent-color business is hard. Something that’s less green in LAB is simultaneously more magenta. The walls are less green than the snow at the outset, but they both have negative A values. Both being green seems improbable, but we have to pick an alternative. Walls neutral and snow slightly green? Walls slightly magenta and snow neutral? Or walls quite magenta and snow slightly magenta? The answer—and mine is, the walls should be slightly magenta and the snow neither magenta nor green—will govern how we handle the key to any successful AB curving: the center point. Every AB curve done so far in this book has kept it constant: we rotated the curve counterclockwise, making sure that it continued to pass through the center of the grid. That’s what we wanted, because until now all neutral colors have been approxi- mately correct. We therefore wanted values of 0 A 0 B —which are what’s at the center point— to remain constant. But that isn’t what we want now. Anything that’s 0 A 0 B in Figure 4.1A must be warmer, and should therefore be positive in both channels. We know this, because we know that objects that should be approximately 0 A 0 B , like snow, are in fact nega- tive in both channels. And so, the curves can’t go through the center point. Instead, they need to pass to the 62 Chapter 4 Figure 4.2 The curves used to produce Figure 4.1B. Note that the A and B curves both pass to the right of the center point, forcing the image toward warmer colors. Left, the Info palette shows numbers for crit- ical areas of the image before and after the application of the curves. Chapter 4. It’s All About The Center Point Page 4 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. right, in the direction of warmer colors, away from green and toward magenta, away from blue and toward yellow. The only questions are how far to the right, and how steep. Figure 4.2’s curves leave the snow slightly on the cool side—typical values of (2) A (2) B . That’s not intentional; I just couldn’t get them all the way to 0 A 0 B while retaining the straight-line shape. With images this weak and grainy, we can’t expect to achieve perfec- tion the first time, in LAB or elsewhere. So, if the format of this chapter didn’t require me to stop here, I would take the image into RGB or CMYK and do further work. It is, however, hard to imagine how we could have gotten even close to where we are now without using LAB . There’s almost no color variation in Figure 4.1A, but the ultra- steep B curve of Figure 4.2 has provided quite a bit. The golden dome has gone from 55 L (6) A 4 B , nearly neutral, to a healthy 60 L 5 A 21 B , which is on the orange side of yellow, not the green side. More impressive, look halfway down the bell tower. It’s framed by two of the onion-shaped domes of the 16th-century Assumption Cathedral behind it. Those start out bluer than the sky, at 47 L (6) A (23) B . One would think that, with the whole picture moving sharply away from blue, they would lose color. They would, too, if this correction were done in any other colorspace. Precisely the opposite occurred here. They’re now a regally blue 48 L 6 A (48) B . Summing up: the contrast-enhancing move in the L curve was introduced in Chap- ter 1, as was the general idea of steepening the A and B curves while keeping them in straight-line form. The notion of using differ- ent angles for each of the AB curves derives from Chapter 3, and pushing them away from the center is the novelty. To verify that we can hit this change of pace again if we need to, we will leave the winter of the world’s largest country to get even chillier in the world’s second largest. Its Fleece Was Green as Snow Québec winters get every bit as nasty as the Russian variety, and so, apparently, do the shooting conditions, which would doubtless be blamed either on acid rain from the province’s southern neighbor or discrimina- tory policies on the part of its western one. Figure 4.3A isn’t as bad as the Sergiev Posad image, but it still needs a big color boost. This time, the cast isn’t bluish green, but rather greenish yellow. The typical values are 88 L (4) A 13 B in the foreground snow; 91 L (3) A 14 B in the large icy tree at right center; 83 L (7) A 9 B about halfway up the sky, which gets slightly bluer higher up. These positive numbers in the B channel confirm the huge yellow cast. After all, the sky is now, ridiculously, more yellow than it is blue. It needs a negative value in the B . Also, as all the A numbers are negative, everything has a green tinge. Before figuring out how to deal with what may be charitably called the color of the image, we get to take a cut at the contrast issue, which is a fat one right down the mid- dle of the plate. The left side of the rock is basically one big reflection, which retouchers call a catchlight or specular highlight. Since such areas contain no detail at all, instead of going with a normal highlight of 97 L or so, we blow it out completely. The lower left corner of the curve moves to the right, until the Info palette reads a pure white, 100 L . Then, since the foreground trees and the sky are both light objects, we increase the slope of the curve in the light (quartertone) area to increase the contrast between them as much as possible. Back to the color. We need to move away from green and toward magenta, so the A curve must pass to the right of the center point, as it did in Figure 4.2. In the last image’s B , however, we were trying to push away from blue and toward yellow, and this time we need to do the opposite. So, the B It’s All About the Center Point 63 Chapter 4. It’s All About The Center Point Page 5 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. Figure 4.3 This winter scene lacks color generally but also contains a yellow-green cast. The corrected version creates a bluer sky and greener trees, and burns out the catchlight in the rock. A B Chapter 4. It’s All About The Center Point Page 6 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. curve now needs to pass to the left of the center point. Both AB curves have to get much steeper if there’s to be any color in this image at all. Ex- actly how steep, and which of the two should be steeper, largely depends on how blue you want the sky to be. There’s no right answer, but my curves are shown in Figure 4.4. 0 A 0 B Isn’t the Holy Grail Trying to force absolute neutrality into areas that are only relatively neutral is a tactic that strikes out many color corrections. The icy tree, for example, is one of the things you might think should be set to 0 A 0 B . So might the foreground snow. However, they can’t both be. They don’t measure the same color in Figure 4.3A, so they certainly aren’t going to be the same after we’ve applied curves that are designed to enhance color variation. If we make the tree 0 A 0 B , the snow will be on the blue-green side of gray, because its AB values are both lower than the tree’s. But if the snow is set to 0 A 0 B , the tree will be on the red side of gray. It’s also permissible to have neither one be neutral. Green is a really ugly color for snow, and anyway it makes sense to me that the icy parts of the tree could be slightly red, if the bark behind them is partially visible. So, I think we need to push the A away from green and toward magenta, and that we shouldn’t stop until the snow reads 0 A . I’m not sure that we need be so doctrinaire with the B . New York children are taught to beware of yellow snow, but probably their mothers are thinking of something at least as yellow as Figure 4.3A. I wouldn’t want that in an image, either. Slightly yellow, now that’s a possibility. When I first tried correcting this image, I went for perfectly neutral, 0 A 0 B snow. Doing that made me think the picture looked too blue, so I backed off. Instead of 88 L (4) A 13 B , it’s 91 L 0 A 6 B : not green at all, but a little less than half as yellow as it once was. I suspect that the presence of a slightly red object as large as the icy tree forces our eyes into seeing the snow as more blue than Photoshop’s Info palette believes. Of course, if you want the snow absolutely white, you could just move the B curve far- ther to the left. Similarly, if you disagree with my decision to make the A curve steeper than the B (I was trying to make the background trees greener, and didn’t want a super-blue sky), you could reverse it. More interestingly, if you wanted to handle blues and yellows as separate items, rather than as equal partners in a single B enhance- ment, you could do that, too. It’s one of the great at- tractions of LAB — but it requires a bit more complex- ity. In every image we’ve done so far, the “curves” in the A and B channels have actually been It’s All About the Center Point 65 Figure 4.4 The curves used to produce Figure 4.3B. This time, the B curve passes to the left of the center point, to move away from blue and toward yellow. Left, the Info palette during the application of the curves. Chapter 4. It’s All About The Center Point Page 7 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. straight lines, albeit at odd angles. They don’t have to be, provided we remember that it’s all about the center point. A Walk in the Park Heading almost due south from Québec lands us in a place with nearly as much sig- nificance in American history as Sergiev Posad has in Russian. Boston Common remains as beautiful an urban park- land as it was in Revolu- tionary days. To keep it that way, we’re likely to want to increase color intensity, particularly in the greens and blues. We won’t be able to do a whole lot with the L channel. Unlike the last two originals, Figure 4.5A has a full range: the whites are white and the blacks are black. We may want to lighten the image slightly to give more range to the horse and rider, which are relatively dark, but that’s about it. Before steepening the AB curves, we need to think about the center point. The huge color casts of Figures 4.1A and Figure 4.5 Applying the normal steepening curves to the AB channels of the top image causes the horse to become quite red. A B Chapter 4. It’s All About The Center Point Page 8 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. 4.3A are absent, but there’s nothing obviously gray that we should be examining to see whether there’s a cast at all. Instead, there are a slew of things that should be in the neighborhood of gray—but not necessarily completely missing all color. Remembering that a perfect gray is 0 A 0 B , that negative numbers represent green and blue, and positive ones magenta and yellow, let’s check numbers. We needn’t bother with the L values, which are irrelevant to whether something is gray. Also, we avoid looking at things that are nearly white or black, because they can’t get very far off 0 A 0 B . We don’t know for a fact that any of the following items actually should be gray, but they all need to be close, and perhaps we can detect a pattern. Here goes. Blaze on the horse’s forehead: (3) A 0 B . Walkway just inside the open gate:(2) A 2 B . Column just outside the fence: (2) A 2 B . Trooper’s hat: (1) A 4 B . His shirt: 0 A 1 B . Street: (3) A (4) B . Plastic garbage bag at lower right: (6) A (16) B . Blanket underneath the saddle: 3 A (7) B . We can start by for- getting the last two items. They may look gray, but they can’t be, particularly the bag. With everything else so close to zero, those big B–negative numbers indicate that the objects must be navy blue. Everything else is negative in the A , mean- ing it’s all slightly biased toward green. I seriously doubt that it should be that way, and would therefore move the A curve very slightly to the right of the center point, away from green and toward magenta. The B readings seem more plausible. I’ll buy that the street is supposed to be a bluish gray; everything else is either neutral or slightly yellow. So, we leave the center point alone, and produce Figure 4.5B. The background looks better, but all I have to say is, that’s a godawful stupid-looking horse. Horses are supposed to be brown, not orange. In Figure 4.5A, he averaged 51 L 25 A 39 B —substantially yellowish red, yet not absurdly so. That got changed to 54 L 46 A 56 B , totally out of hand. What’s needed is something like Figure 4.6, which intensifies the cool colors—note how the grass is greener and the sky bluer than in It’s All About the Center Point 67 Figure 4.6 The AB curves of Figure 4.5 are modified by adding a center point to each and forcing the top half to be steeper than the bottom. This enhances cool colors while holding warm colors roughly constant. Chapter 4. It’s All About The Center Point Page 9 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. Figure 4.5A—while not permitting drastic changes in the warm ones. To achieve it requires making real AB curves—not just angled straight lines. Each curve has a top (cool) and bottom (warm) half, but to exploit them separately we need to take care with the center point. So far, we’ve never actually clicked a point into the center of the curve grid, because there was no point in doing so: straight lines are easy to maneuver through any arbitrary center point we might choose. But now, that approach has to change. At least in the A , the bottom half of the curve needs to be flatter than the top, so that the magenta component doesn’t get punched up as much as the green. The A curve of Figure 4.6 looks very foreign to anyone accomplished with curves in RGB , CMYK , or grayscale. In those colorspaces, one would never do anything like what’s hap- pening in the lower left corner. Otherwise, anything that used to be a pure white would become darker, annihilating contrast. In the A channel (and the B likewise), we yawn at such considerations. This curve shape merely means that 127 A , which is about as frequently seen in the real world as a bat- ting average above 1.000, will become some- thing like 110 A , which is no more common than a seven-run homer. You don’t have to worry about these areas of the curve, because they’re far out of the gamut of anything you’ll ever output to, and even if they weren’t, they cover brilliant reds and yellows, of which there are none in this particular photograph. The only areas of real concern in the bottom half of the curve fall in the first two gridlines beneath the center. Each gridline is worth roughly 25 points in the A or B . So, the point one gridline down from the center point covers the horse, which started at 25 A . Since that point doesn’t change from its original position, the magenta-as- opposed-to-green component of the horse won’t change either. The B curve in Figure 4.6 is a variation on the same theme. There’s a point in the middle to prevent anything that was 0 B from chang- ing to something else. The top of the curve is very steep, to accentuate the blues. The point two gridlines below the center covers the horse, preventing it from getting more yellow. As to why the bottom quarter of the curve hooks to the right, as opposed to the A curve, which hooks to the left, that question can be left to the philosophers. Nothing in this pic- ture is more yellow-as-opposed-to-blue than the horse is. Therefore, provided that there’s an equine locking point, it won’t matter whether the lower left point is found higher up, more to the right, or on the moon. A Horse Is a Horse, of Course, of Course The move in this Boston Common scene— adjust the center point, adjust each half of the curve—is so fundamental to working in LAB that I’ll end this section with a hanging curve ball: an image that’s handled in almost exactly the same way. Figure 4.7A is a better original than Figure 4.5A was, but otherwise is a horse of the same color, minus the horse, of course, of course. Trying for more intense blues and greens is a noble objective that has been achieved in Figure 4.7B, at the horrific cost of blinding the viewer with ridiculous reds. Now that we’ve seen the wrong way to do it, it’s up to you to do it the right way. There’s no need to show it here, because the raw image is on the CD .It would be handled in much the same manner as Figure 4.6. That is, the AB curves would be divided in half, and the cool colors emphasized while the warm ones would stay close to their original values. I’ll make some quick observations about how to do it, and terminate this part of the chapter 68 Chapter 4 Figure 4.7 (opposite) It may seem tempting to try to enhance the greens and blues in the top version, but using standard straight-line AB curves creates radio- active reds (below). Chapter 4. It’s All About The Center Point Page 10 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. A B Chapter 4. It’s All About The Center Point Page 11 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. with a move that produces an even worse result than Figure 4.7B, if possible. The brightest part of the house is 99 L 0 A 0 B . Straight above the third red column is a cloud whose lightest area averages 98 L (8) A (6) B . The column itself checks in at 80 L 29 A 13 B . The deepest shadow, in the greenery to the left of the house, averages 5 L (3) A 0 B . Interpretation: the house values sound right, but we don’t really know. The clouds are greenish-blue, which seems highly doubtful. The columns are whatever they are. Knowing their values is helpful only insofar as we prevent them from becoming intensely red by planting appropriate holding points on the AB curves. And the shadow, slightly green, seems appropriate for the middle of a grove of trees. Getting the right balance is an exercise left to you. You should probably leave the L Figure 4.8 A “correction” of Figure 4.7A that goes overboard in reducing the impact of the reds. Below, the AB curves that created Figure 4.7B. Left, the weirdly humped A curve that was substituted to produce the image above. The L channel is untouched in all three versions. Chapter 4. It’s All About The Center Point Page 12 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: Peachpit Press Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Print Publication Date: 2005/08/08 User number: 910766 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited. [...]... shoot for perfect endpoints, whether using drum scanner, Camera Raw, or LAB If not, however, you should be more conservative Particularly, in Camera Raw, adjusting the Exposure setting lets you Figure 4.9 The four primary and four secondary colors in the LAB channel structure Chapter 4 It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Prepared... channels, particularly in CMYK In LAB, the operative word is not frequently but always To limit yourself to a single channel, the keyboard shortcut is (and before going on, please read the box on the opposite page) Command plus the number that corresponds to the channel In LAB, Command–1 would select only the L , Command–2 the A , and Chapter 5 Sharpen the L, Blur the AB Photoshop Lab Color: The Canyon Conundrum:... original was Photoshop 6 (2000) introduced the Cona lot flatter than this one, and thus might vert to Profile command, which I’ve been need more aggressive correction recommending but which we could surely Photoshop CS2 Launches a Winner live without Far more significant was the introduction in Photoshop CS (2003) of the Retouching and correction technique doesn’t change much over the years Photoshop. .. to eliminate it in RGB or CMYK often causes a loss of detail Below, a new blue channel that was created by converting the file to LAB, applying the Dust & Scratches filter to the B channel, and then reconverting the file to RGB Chapter 5 Sharpen the L, Blur the AB Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com... moment, we’ll stick with basic principles Blurring to reduce noise works so much better in LAB that it’s worth converting out of RGB to do it I am not convinced that it’s worth converting to LAB if you plan to do nothing but sharpening there; but if you are already there and plan to sharpen the image overall, LAB is where you should do it Selecting a Single Channel Sharpening and/or blurring are sometimes... sophisticated crowbar, Photoshop s Camera Raw Camera Raw, introduced during the reign of Photoshop 7 and now significantly improved, requires a raw capture—not a JPEG—from certain brands of digital camera It is strikingly analogous to the old-fashioned way of doing things: Camera Raw is the drum scanner, you are the operator In a strange way, both are analogous to curving in LAB And the same piece of... channel The noise would provoke some image technicians to launch one of Photoshop s many blurring filters, any of which may tone down the damage and all of which will harm contrast if applied to any channel in RGB or CMYK The space-age method of eliminating the colored noise is to convert Chapter 5 Sharpen the L, Blur the AB Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Prepared... entire book This isn’t the one My Professional Photoshop series offers a more in-depth explanation Lots of variations exist, such as separating the darkening and lightening actions of the filter onto separate layers, sharpening through a mask, or Filter: Sharpen>Smart Sharpen (Photoshop CS2 or later only), which permits a bit of both All such methods work in LAB, often better than in other colorspaces... know that? I’ve never met this woman, so I don’t know her hair color Nevertheless, even if the color of this original is all wrong, the hair is too dark for Chapter 4 It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher:... otherwise violates the Safari Terms of Service is strictly prohibited Chapter 4 It’s All About The Center Point Page 20 Return to Table of Contents A B Chapter 4 It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Prepared for Sudharaka Dhammasena, Safari ID: sudharaka@ceybank.com Powerful Colorspace By DAN MARGULIS ISBN: 0321356780 Publisher: . four secondary colors in the LAB channel structure. Chapter 4. It’s All About The Center Point Page 15 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon. Center Point Page 3 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN. Center Point Page 4 Return to Table of Contents Chapter 4. It’s All About The Center Point Photoshop Lab Color: The Canyon Conundrum: And Other Adventures in The Most Powerful Colorspace By DAN