Mac OS X: Advanced Color Management

Overview

The HP PhotoSmart 7960 Mac OS X color management solution was designed to meet a broad range of customer needs. For customers with little imaging expertise, default automatic color processing delivers good looking results. For users that desire professional color control, printer driver settings enable advanced color management features, including support for ICC color management*.

* Support for ICC profiles is available in printer driver version 2.3.7 and later. ICC enables profile-based color management solutions. ColorSync is a specific implementation of ICC color management. For more general information on ICC color management, please see www.color.org.

Color Management settings in the printer driver

The printer color management choices are accessed under the Paper Type/Quality section in the Print dialog. Typically, one would access these options by selecting File… Print…. Paper Type/Quality .

For color printing, the Color menu allows the user to select the specific color space that the printer will use to interpret image data. The default setting is ColorSmart III (sRGB) , which is the standard color space for virtually all cameras, scanners, monitors, and Web page documents. The ColorSync selection enables driver-based color management. Selecting ColorSync tells the printer driver to specify one of its device profiles as the destination color space.

For printing black and white photographs, Grayscale should be selected. In addition, the printer should be configured with the HP 59 gray photo cartridge.

Creating black and white photos in Adobe Photoshop

The process of printing a black and white photo often begins with an original color image. If the image is color, and Grayscale is selected in the printer driver, the printer will convert the image to black and white before printing. However, the conversion of a color image to grayscale is a subjective and artistic process, so many photo enthusiasts will want to control this conversion.

One of the best ways to control the conversion from color to black and white in Photoshop is with the Channel Mixer. This feature is accessed in Photoshop by selecting Image… Adjustments… Channel Mixer .

To create the black and white image, select the Monochrome checkbox, and adjust the Red, Green, and Blue sliders to find the desired artistic effect. The following two images demonstrate the effect of controlling channel mixing:

The image on the top was converted to grayscale using the Image… Adjustments… Desaturate function. The image on the bottom was converted with the Channel Mixer using the settings shown above.

Color management for black and white photos in Adobe Photoshop

The grayscale tone reproduction of the HP PhotoSmart 7960 printer is optimized for the sRGB gamma. This gamma function is approximately 2.2, so Adobe RGB source images should also give reasonable results. However, in applications with advanced color management features such as Adobe Photoshop, black and white images that are encoded in virtually any color space can be printed on the 7960.

For example, images encoded in the Apple’s Generic RGB space have a gamma of 1.8. To more accurately print these images make sure that the source and destination color spaces are properly configured. In Photoshop 7 and CS, this can be done in the File… Print with Preview dialog:

Here, the image source space is known to be Generic RGB, and the Print Space profile is set to PostScript Color Management (version 7.0) or Printer Color Management (version CS). With these settings, gamma 1.8 grayscale images will be converted to a gamma of 2.2 for better print fidelity. More information on how these settings are used for color management is provided in the next section.

The best quality black and white prints will result when

• The printer is configured with the HP 59 gray photo cartridge
• The printer driver is set to Grayscale, and
• The correct paper type is selected in the printer driver

Tip : If you temporarily run out of color ink, you can still print black and white photos by removing the color print cartridges. The printer will print in reserve mode, which utilizes the available cartridge.

Using ICC profiles for color photos in Adobe Photoshop

High-end imaging applications, such as Adobe Photoshop, provide support for ICC color management. For printers, ICC profiles provide the color transform into the device color space of the printer, for a particular media type, ink set, and print mode.

To manage color with ICC profiles, settings must be made in both the application and in the printer driver. In the application, the correct profile setting must be selected, along with the rendering intent (perceptual, relative, absolute, or saturation**). In the driver, the media type, quality mode, profile and ColorSync must be selected.

** The Perceptual Intent includes color re-rendering such as tone scaling and sophisticated gamut mapping to give pleasing output. It generally gives the best subjective image quality when reproducing images on different media. Absolute Colorimetric and Relative Colorimetric are usually used for proofing, where accuracy is more important than subjective quality. Saturation is seldom used, but is intended to give vivid colors and pure primaries.

To use HP provided ICC profiles when printing an image from PhotoShop:

• Select File… Print with Preview . (For Photoshop 6 and prior, select File… Print )
• For Photoshop 7 and CS, In the Print with Preview Dialog, select Show More Options checkbox, and Color Management from the menu.
• In the Profile menu, select the PostScript Color Management (version 7.0) or Printer Color Management (version CS). The PostScript Color Management option, in versions 7.0 and prior, is a bit confusing since the Photosmart printer is not a PostScript printer. This setting was renamed in version CS to Printer Color Management. Basically, this setting tells Photoshop to embed a source profile in the print job.
• Set the ICC rendering intent in the Intent menu. Most users will want to use the Perceptual intent to give the most subjectively pleasing color reproduction.
• The driver must also be configured to properly use the profile. This is done by first selecting Print… Paper Type/Quality… and selecting ColorSync from the Color menu.
• In addition, the correct paper type must also be selected.
• Next select Color Options and verify the Installed Print Cartridges setting matches the set of print cartridges in the printer. The ColorSync profile will display the destination profile selected by the printer driver.
• Click Print .

Creating custom ICC profiles

Often, advanced users who want the highest degree of color control will want to generate their own ICC profiles using 3rd party profiling applications available from independent software vendors such as Monaco, ColorBlind, Color Savvy, and GretagMacbeth. By creating custom profiles, users can color-correct for the exact paper, print cartridges, and printer that they are using.

This process generally involves printing a large set of color patches with color management turned off. The printed color patches are then measured with a spectrophotometer, and finally, the measured reflectance data is used in conjunction with a profiling application to compute a new ICC profile. Please refer to the instructions provided with specific 3rd party profiling applications for more details on this process.

To print color target images, the driver’s profile will need to be overridden in the ColorSync Utility to match the color target’s profile. The matching source and destination profiles will prevent any color conversion when the target is printed. In the driver, the ColorSync feature should be selected, along with the paper type.

To print a color target in Adobe Photoshop 7 and CS:

• First run the ColorSync Utility , select Devices in the toolbar, expand the Printers list, and finally expand the list for the device to be profiled.
• Select the profile matching the paper type and print cartridge set to profile. Next, change Current Profile setting to match the color target’s profile.
• Open the profile target image in Photoshop and select File… Print with Preview . (For Photoshop 6 and prior, select File… Print ).
• Select the Show More Options check box, and Color Management from the pull-down menu.
• In the Profile menu, select PostScript Color Management (versions 7.0) or Printer Color Management (version CS) .
• As in the previous example, the driver must also be configured. This is done by first selecting Print… Paper Type/Quality… and selecting ColorSync from the Color menu, selecting the paper type from, and verifying the Installed Print Cartridges in the Color Options dialog. Finally, click Print .

With these settings, a print without any color management intervention from either the driver or the application will be produced. This print is suitable for measurement and profile creation.

Finally use the ColorSync Utility, as described earlier, to override the hp profile with the newly created profile or use the Set to Factory option to restore the hp (default) profile.