Page #132 (Chapter 13. Making Quick Corrections to a Photograph)


103. About Color Management

See Also

66 Print an Image

104 About Adobe Gamma

105 Ensure That What You See Is What You Get


What you see onscreen when you view an image is often very different from what you get when you print an image on paper. Not only do your monitor, printer, and even your scanner use different methods to render color images, each device works with its own separate range of possible colors (also called a gamut). What this means is that, when representing an image onscreen, your monitor might display a grayish red for an area of an image, which is not reproducible by your printer as an exact match. The printer, in such a case, simply substitutes a close match to the grayish red from similar colors in its gamut. So, when the image is printed, you get something that's close to what it looked like onscreen, but not exactly. The best way you can deal with this messy situation is to create an environment that simulates onscreen (as nearly as possible) what an image will look like when it's finally printed. To do that, you use color management.

Why Manage Colors?

One of the tasks of color management is to match the gamut of colors your monitor uses with the gamut of colors your printer is capable of reproducing so that, in the best of all worlds, what you see onscreen as a "pale shade of greenish-blue" approximates that shade when printed. If the color of your son's shirt is a bit off when you print a photo, you might not even notice, but if his skin tone carries a slight greenish cast, it'll stick out like a sore thumb and the whole image will look "off."

KEY TERMS

Gamut A palette comprised of all the individual colors that can be reproduced by a device. Your monitor and your printer each have separate gamuts, and sometimes colors within them might match closely but not precisely.

Color management The process of coordinating the color gamut of your monitor with that of your scanner and printer so that the same colors are reproduced throughout your system.


When what you see onscreen is not what you get when an image is printed, you need color management (in this example, the girl's skin tone, hair color, and even the color of the tractor is different). See the Color Gallery to compare these two images.

Microsoft Windows has the unenviable task of translating colors from one device to another using specific ICM (Image Color Management) profiles for the devices involvedcommonly called ICC color profiles. All devices that use color should have one of these profiles installed (your monitor, printer, and scanner). Typically, the profile is located on the manufacturer's disc, and you install it at the time you install the device driver and other software. With a profile installed, Windows shifts its color gamut to match the device's specifications, so that "rosy red" shows up as exactly that on your monitor, printer, and scanner.

TIP

Because paper plays a critical role in the quality of photos printed at home, manufacturers of paper for inkjet and photo printers are now releasing ICC color profiles for their various grades and bonds of paper. How you use one of these profiles depends on how your printer driver manages color. Newer printer drivers can incorporate separate paper profiles along with their existing printer profiles. Some printer manufacturers' brands of paperfor instance, HP and Epsonprovide color profiles that override the existing profiles for their older models of printers (those that don't manage paper profiles separately), thus becoming combination "printer + paper" profiles.


In the absence of an ICC color profile for a device (if you haven't installed one for your printer, for example, or you simply couldn't find one on a disc or at the manufacturer's Web site), Windows uses its own color gamut instead. The video card then takes over the job of trying to represent colors on the screen with accuracybasically by overriding the Windows default gamut with the one in the monitor's ICC profile. Photoshop Elements takes this one step further by making minor adjustments to these colors with some help from a program called Adobe Gamma.

Digital Cameras, Printers, and EXIF Data

Photoshop Elements uses information from separate camera ICC color profiles, when they are available. But both the Editor and the Organizer typically rely on EXIF information embedded within each of the images being imported, about how the camera perceived color at the time it took the picture. It is this information, specifically, that describes the camera's gamut. This is why proper photographic practices, including white balancing, are so important: When white looks the way it should for your digital camera, a calibrated monitor will precisely re-create that shade of white so that you won't make color adjustments to photos that might not really need them. For most digital cameras, the gamut used is sRGB. If you turn color management on within the Editor, the gamut used by the digital camera (and included in an image's EXIF data) is then used to translate that same information to the screen. For images that don't have a gamut listed in their EXIF data, you can choose which gamut to use. Again, sRGB is the gamut typically used by most digital cameras, so it's a good choice for use in the Editor when opening an image.

NOTE

Adobe Gamma creates an ICC color profile of its own, using information provided by the video card through Windows. The resulting profile is what Photoshop Elements uses to represent colors onscreen. You'll learn how to make adjustments to the choices Adobe Gamma makes in 105 Ensure That What You See Is What You Get.


The color gamut information attached to image files follows a standard adopted by all major camera manufacturers (and some scanner manufacturers) called Exchangeable Image File Format (EXIF). EXIF data helps Photoshop Elements (and other graphics editors) determine where the camera's interpretation of "pure" red, green, and blue (the optical primary colors) are located on a theoretical chart of all visible colors. Photoshop Elements can then compare these coordinates to where its own "pure" primary colors are located on the same theoretical chart. After the program knows how to adjust these three pure colors, it can mathematically determine how to adjust all the other colors so that it displays onscreen what your camera saw when the image was recorded. The EXIF data is in turn used by most photo printers when an image is printed, so again, you get a pretty good printout of what the camera saw when the photo was taken.

NOTES

If you want the Adobe Gamma profile to be used by other programs, make that selection from the Color Management tab of your video driver: double-click the Display icon in the Control Panel, click the Advanced button on the Settings tab, click the Color Management tab, and select the Adobe Gamma profile.

Some newer models of digital cameras have their own color profiles. An application that supports a camera color profile can use this information to help accurately translate color from the camera to the monitor. The goal of the digital camera ICC profile is to minimize information loss during the color translation from camera to monitor as much as possible.

As explained in 53 About Image Information, you can view the EXIF data for an image by displaying the File Info dialog box (in the Editor) or by looking on the Metadata tab of the Properties pane (in the Organizer).


You can view the EXIF data attached to an image using the Editor or the Organizer.

Some printers do not interpret EXIF data. Instead, they rely on Windows to provide them with a standard set of colors to use when printing an image that has EXIF data. This set of colors, by the way, has been re-interpreted at least once by the imaging program (such as Photoshop Elements) that imported the image file from the camera. This system is pretty good, but printer manufacturer Epson decided to do it one better.

NOTE

Some cameras tag their images with the sRGB color space (gamut), even if that is not the actual gamut used by the camera. This causes a noticeable color cast in all the camera's images when viewed onscreen (when Photoshop Elements assumes that sRGB was actually used, and uses that gamut to display the image onscreen). When your digital camera is pretending to use sRGB and it really isn't, you'll want to ignore the EXIF data when saving an image and have Adobe Gamma provide the color space data instead. Simply choose Edit, Preferences, Saving Files from the Editor menu, enable the Ignore Camera Data (EXIF) Profiles check box, and click OK.


Recently, Epson has engineered a system for its inkjet and photo printers that gives the printer the EXIF data for an image directly, by way of a bypass driver. Epson calls its system Print Image Management (PIM), and it enables its printers to see with a high degree of accuracy (albeit through two translators) what a PIM-enabled digital camera saw when it recorded an image. This way, "black" in the digital image (which optically is comprised of no red, green, or blue whatsoever) translates into "black" on the printed page (which, for pigment, generally involves a mixture of black ink with equal parts of cyan, magenta, and yellow inks). Essentially, PIMand its successor, PIM IIensure that both the Epson printer and the PIM-enabled digital camera interpret color and present EXIF data in the same way. If you plan to use the PIM feature of your printer as it was intended, you should purchase or use a digital camera that explicitly supports PIM as welland thankfully, many do, but you do have to look.

When PIM is involved, the color management scheme changes. Software called the PIM plug-in bypasses Windows color management and the ICC color profile, presenting EXIF data from an image directly to Photoshop Elements. The status of the PIM coalition changes often; as a result, other printer brands (such as Canon) might also be PIM enabled. Consult your printer's documentation to learn whether it is PIM enabled.



Adobe Photoshop Elements 3 in a Snap
Adobe Photoshop Elements 3 in a Snap
ISBN: 067232668X
EAN: 2147483647
Year: 2006
Pages: 263

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