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Color Conversion Central
As I mentioned near the outset of this chapter, Color Settings is the command that puts Photoshop's color conversion functions in play. It at once defines the color space parameters and makes the color conversions happen. This section explains the specific options as they're grouped in the Color Settings dialog box. I also make suggestions for what I consider to be the optimal settings, in case you're interested in a little advice.
Description
This portion of the dialog box comes last, but it's also the most important. It tells you what every one of the Color Settings options does. Just hover the cursor over an option to see a detailed description. To see how an option in a pop-up menu works, select the option and then hover your cursor over it. With help like this, what do you need me for?
No seriously, what do you need me for? I think I'll take the rest of the chapter off. Well, I guess I could mention that if you save your own color settings, you can enter a description that shows up here in the Description section when you load your settings. There, I suddenly feel important again.
Working spaces
Because every color model except Lab varies according to the hardware — the screen or the printer — Photoshop has to tweak the color space to meet your specific needs. There's no such thing as a single, true CMYK color model, for example. Instead, there are lots of printer-specific CMYK color models. These color models inside color models are called working spaces. You define the default working spaces that Photoshop uses when opening unprofiled images, creating new ones, or converting mismatched images using the four Working Spaces pop-up menus:
RGB: The RGB environment defines what you see on screen. Rather than limiting yourself to the circumscribed range of colors that your particular brand of monitor can display — known as the monitor's gamut — you can work in a larger, richer color environment, filled with theoretical color options that will serve your image well when projected on other monitors and output from commercial presses. Unless you work strictly on the Web and never create artwork for print, I suggest you select Adobe RGB (1998). If you're working with images destined for After Effects, Adobe recommends that you choose the Monitor RGB working space. Notice that your monitor space also appears in the pop-up menu — this shows that your monitor was correctly tagged with Adobe Gamma or the Display Calibrator Assistant.
| Tip | If you're a Web artist and you want to preview how an image will look on a different kind of monitor, choose the color space from the View Proof Setup menu after closing the Color Settings dialog box. For example, choose View Proof Setup Windows RGB to see how the image looks on a typical PC monitor. Choose Macintosh RGB for a typical Mac monitor or Monitor RGB to turn off the RGB working space and see the image as it appears without conversion. Then use Ctrl+Y (Win) or z -Y (Mac) to turn the preview on and off. All these commands work identically regardless of which working space you select, so you might as well use Adobe RGB, the choice most likely to put you in sync with other professionals. |
CMYK: Use this option to specify the kind of printer you intend to use to print your final CMYK document. This option defines how Photoshop converts an image to the CMYK color space when you choose Image Mode CMYK Color. It also governs the performance of the CMYK preview (View Proof Setup Custom CMYK Setup" later in this chapter.
Grayscale: This command defines how Photoshop displays a grayscale image (created using Image Mode Grayscale). You can adjust the gray values in the image to account for a typical Macintosh or PC display (Gray Gamma 1.8 or Gray Gamma 2.2, respectively). Or preview the image according to how it will print, complete with any of several Dot Gain values. (Dot gain is the factor by which halftone dots grow when absorbed into paper, as I discuss in the upcoming "Custom CMYK Setup" section.) My preferred setting is Gray Gamma 2.2. It's dark enough to account for dot gains of more than 25 percent, so it accurately reflects the printing conditions typical of grayscale work. Plus it predicts how grays display on a typical PC monitor. Everybody wins.
Spot: From a printing perspective, a spot-color separation behaves like an extra grayscale print. Specify the dot gain value that correlates to your commercial printer. If you don't know that value, Dot Gain 20% is a safe bet.
| Note | An open profiled image remains in its working space regardless of how you change the settings in the Color Settings dialog box. Suppose that you open an image in sRGB and then change the working space to Adobe RGB. The open image remains unchanged on screen, safe in its sRGB space. If you'd prefer the image to change to the new space, choose Image Mode Assign Profile. Then select the Working RGB radio button, as shown in Figure 16-9. Because Assign Profile leaves the color values of all pixels unchanged, Photoshop merely displays the old pixels in the new space, which permits the colors to shift on screen. So perhaps perversely, not converting pixels results in a visible color shift, whereas converting pixels does not.  Figure 16-9: Use the Assign Profile command to switch an open image to a different color space without converting pixels. As a result, the image will look different on screen. |
If the Assign Profile command leaves pixels unchanged so that they appear to change on screen, there must be a command that converts pixels so that they appear consistent on screen. Sure enough, that command is Image Mode Convert to Profile, which displays the dialog box pictured in Figure 16-10. The options in the lower half of the dialog box — Engine, Intent, and so on — also appear in the Color Settings dialog box when you enter the advanced mode, so you'll be hearing more about them later. For now, just select the color space that you want to convert the image to from the Destination Space pop-up menu and press Enter or Return.
Figure 16-10: Convert to Profile is the complement to Assign Profile. Choose it to both switch an open image to a different color space and convert the pixels. The result is an image that looks the same on screen as it did before.
| Tip | On first glance, the Destination Space pop-up menu may seem wildly complicated, offering RGB, CMYK, and grayscale working spaces, and even going so far as to permit you to create your own. But in fact, this dizzying array of options may in some situations lead to less work for you. The Destination Space option is unusual in that it permits you to switch color modes. For example, if you open an RGB image, choose the Convert to Profile command, and select a CMYK space such as U.S. Web Coated (SWOP), Photoshop not only remaps the colors, it converts the RGB channels to CMYK. In this way, Convert to Profile has an edge over Image Mode CMYK Color — you can switch color modes and nail a specific working space in one operation. |
Color management policies
Highlighted in Figure 16-11, the next set of options control how Photoshop reacts when opening an image that either lacks a profile or contains a profile that doesn't match the specified Working Spaces options previously listed. These are the options that are most likely to cause confusion because they're responsible for the error messages Photoshop delivers when opening images. The trick is to keep the error messages to a minimum while keeping control to a maximum. Here are my suggestions for each option with what I hope is enough explanation for you to make your own educated decisions:
Figure 16-11: Here are my recommended settings for the five Color Management Policies options. They tell Photoshop to ask you when opening images with mismatches, but otherwise proceed automatically.
RGB: The first three pop-up menus establish default policies that Photoshop suggests or implements according to the check boxes that follow. For example, when opening an untagged RGB image, I reckon I might as well tag it with the working RGB profile, which in my case is Adobe RGB. So I select Convert to Working RGB and turn the Missing Profiles check box off. This way, when no profile is evident, Photoshop assigns the Adobe RGB profile without bothering me. However, if the image contains a profile, I might go either way. An image tagged with an sRGB profile is probably a Web image, so I might go ahead and open it in the sRGB space without conversion. However, if I encountered an image tagged with the Apple RGB profile — intended to match a typical Apple Macintosh screen — I'd want to convert it to Adobe RGB. Therefore, I set Profile Mismatches to Ask When Opening. This way, Photoshop will ask me what I want to do every time I open an image with a nonmatching RGB profile. It will suggest that I convert the image to Adobe RGB but permit me to override it if I like.
CMYK: Whereas RGB color is a function of your monitor and the RGB working space, accurate CMYK is all about matching colors to a specific output device. Therefore, if you're accepting CMYK images from clients and colleagues, you probably want to be very careful about making arbitrary conversions. By setting CMYK to Preserve Embedded Profiles, I tell Photoshop to open a tagged CMYK image in its own color space and override the default CMYK space specified in the Working Spaces option mentioned previously. Again, setting Profile Mismatches to Ask When Opening gives me the option to change my mind and convert the image to my working CMYK space if I deem it appropriate. If the image has no profile, Photoshop leaves it untagged, giving me the option of testing out multiple CMYK working spaces and assigning the one that fits best.
Gray: Making automatic color manipulations to color images is all very well and good. Clipping is bound to occur, but with millions of theoretical colors at your disposal, the clipping is unlikely to do any visible harm. However, grayscale images are another story. Blessed with just 256 brightness values, they are significantly more fragile than color images. Furthermore, few grayscale images are tagged properly, making Photoshop's automatic adjustments highly suspect. The upshot is that I prefer to correct grayscale images manually (as explained in Chapter 17) and keep Photoshop the heck out of it. Therefore, I set the Gray option to Off.
Profile Mismatches: These two check boxes tell Photoshop how to behave when opening an image whose profile does not match the working color space. If you select the Ask When Opening check box, Photoshop asks your permission to perform the conversion suggested in the previous pop-up menus. As the top message in Figure 16-12 shows, you also have the option of opening the image in its native color space or leaving the image untagged. Back in the Color Settings dialog box, select Ask When Pasting to tell Photoshop to warn you when you copy an image from one working space and paste it into another. Shown at the bottom of Figure 16-12, this warning is a bit much, in my opinion. In all likelihood, you want Photoshop to convert the colors, so turn off Ask When Pasting and let Photoshop do its work unhindered.
Figure 16-12: The alert message that appears when opening an image with a mismatched profile (top) and then copying part of that image and pasting it into an image that subscribes to the default working space (bottom).
Missing Profiles: When you open an image that lacks an embedded profile, Photoshop likes to ask you whether you want to manage the colors or not. I say turn off Ask When Opening — enough alert messages already! — and let Photoshop take its cues from the RGB, CMYK, and Gray pop-up menus. According to Figure 16-11, this means Photoshop will tag most unprofiled RGB images with an Adobe RGB profile and leave unprofiled CMYK and grayscale images alone. An exception occurs when opening newer unprofiled images. If you saved an image without a profile using Version 5 or later, Photoshop inserted a tag that explicitly states, "I have no profile." In this case, the file will open untagged and Photoshop will resist color managing the image until you tell it to do otherwise.
The Color Management Policies options are particularly dense, so I don't blame you if you find yourself reading and rereading my text trying to make sense of it. If you can't for the life of you make heads or tails of what I'm talking about — if it's any consolation, I'm honestly not trying to confuse you — try this instead: Set your options to match the ones I've suggested in Figure 16-11. Then work in Photoshop for a few days or weeks and see how it feels. The good news about my suggestions is that they won't hurt your images, even if you don't know what you're doing. With a little time and practice, you'll get a feel for how the settings work. Then come back, read my text again, and see if it doesn't make more sense. I wouldn't be surprised if it suddenly seems crystal clear.
Advanced mode
Right about now, I picture you scratching your head and thinking, "Wow, this Deke guy really gets off on color management. I mean, dude, give it a rest already!" I have to admit, I do find color management profoundly interesting. It inspires the same twisted feelings I have when watching a highway expansion project. On the one hand, I have to admire all that planning and organization. I mean, gee whiz, what a lot of work, all so I can get to the grocery store faster. But on the other hand, I think surely there has got to be a better way. If these guys would only put this kind of effort into flying cars, I'd be home by now.
Up to this point, my admiration for Photoshop's color management has outweighed my frustration. But the moment I select the Advanced Mode check box, my patience evaporates. Suddenly, this really is too much. But a book called the Bible has a responsibility to cover everything, so I guess I'm stuck with it.Think of the Advanced Mode check box as the key to the color management underworld. When you select it, you unleash two categories of demonic preference settings: Conversion Options and Advanced Controls. Spotlighted in Figure 16-13, each set of options possesses its own special brand of loathsome and horrible power. For the love of God, dear reader, run away now while you still can.
Figure 16-13: Turn on the Advanced Mode check box to display the Conversion Options and Advanced Controls, as well as define your own CMYK working space.
Okay, perhaps that's a bit of an exaggeration. So what the heck, let's give it a whirl. Perhaps even hell can be fun if we give it a chance:
Engine: The first of the Advanced Mode options is Engine, and it does just what it sounds like it does. The force behind the color management process is the engine. If you don't like one engine, you can trade it for another. If you work in a Macintosh-centric environment, for example, you might want to select Apple ColorSync. But I recommend you stick with the Adobe Color Engine, or ACE. Not only is ACE a great engine, it ensures compatibility with Illustrator, InDesign, and other Adobe applications.
Intent: Whenever you remap colors, a little something gets lost in the trans-lation. The trick is to lose as little as possible, and that's the point of Intent. In previous versions of Photoshop, the option was set by default to Relative Colorimetric, which converts every color in the source profile to its closest equivalent in the destination profile. Although such a direct transfer of colors may sound attractive, it can create rifts in the image. The closest equivalent for two similar colors in the source profile might be a single color in the destination, or they might be two very different colors. As a result, gradual transitions may become flat or choppy. Wisely, Adobe has now set Perceptual as the default, which sacrifices specific colors in favor of retaining the gradual transitions between colors, so important to the success of continuous-tone photographs.
| Tip | Why should you take my word that Perceptual is better? You shouldn't. To get a second opinion, hover your cursor over the word Perceptual and read the Description text, which tells you that Perceptual "requests a visually pleasing rendering, preserving the visual relationships between source colors." The truth is, most folks at Adobe believe Perceptual to be the better choice. |
Use Black Point Compensation: Like any other colors, Photoshop wants to convert black and white to new values. Whites are compensated naturally by the Intent setting, which may in many cases map white to a different color in the name of smoother transitions. But if you let black map to a lighter color, you can end up with wimpy gray shadows. To keep your blacks their blackest, turn on this check box.
Use Dither (8-bit/channel images): Just so we're all on the same page, a 24-bit image contains 8 bits per channel. So don't think we're talking about 8-bit GIF images here; this option uses dithering (random patterns of pixels) to smooth out what might otherwise be harsh color transitions. Ostensibly, it can result in higher file sizes when saving an image in the native PSD format or TIFF with LZW compression. But the effect is usually minimal. Leave this check box turned on.
Desaturate Monitor Colors By: The Adobe RGB space in particular has a habit of rendering such vivid colors that the brightest areas in the image flatten out on screen. Because they may or may not have a direct outcome on the appearance of the final image, whether in print or on the Web, such flat areas can be a bit misleading. To better see details in bright areas of color, turn on the Desaturate Monitor Colors check box. Note that this option affects only the screen view; the colors will continue to print as vividly as ever. I recommend that you use this option only for running previews in the Color Settings dialog box. Leaving this option on for extended periods of time can be more deceiving than turning it off.
Blend RGB Colors Using Gamma: When this option is off, as by default, Photoshop blends layers according to the gamma of the working color space. For example, the gamma of Adobe RGB is 2.2, the same as a typical PC screen and a few shades darker than a typical Macintosh screen. On occasion, however, this may result in incongruous highlights around the edges of layers. If you encounter this, try turning on this check box. Photoshop recalculates all blends using a theoretically more desirable gamma value.
