ColorSync™ 2.5 is the latest version of Apple Computer's color management architecture for the Mac OS. This document describes the new capabilities provided in version 2.5.
What’s New
The latest version of ColorSync provides new and enhanced features in several areas:
- Monitor calibration
- AppleScript support
- Profile cache file
- Profiles folder and subfolders
- Photoshop plug-ins
- Multiprocessing
- 16 bit support
Monitor Calibration
Open up the Monitors & Sound control panel and you’ll notice some changes, namely the addition of the ColorSync Profiles panel showing a list of profiles.
You might also notice that the list of monitor gammas (Mac Standard Gamma, Uncorrected Gamma) has been removed, since the setting of gamma has been moved into the calibration process. Clicking on the “Calibrate” button brings up the Monitor Calibration Assistant, which looks a lot like other Assistants you’ve probably used before. The assistant walks you through a series of screens with helpful text describing the purpose of each step in the process.
The assistant helps you create a “profile” of your monitor that describes the gamut of your monitor based on its phosphor set, the inherent gamma of your monitor, the gamma you’re trying to achieve, the white point your monitor is set to, and the white point you’re trying to achieve. After you’ve created a profile, it shows up in the list of available profiles.
The Monitor Calibration Assistant which appears when you click on the “Calibrate” button is part of the Default Calibrator, the software-only calibrator supplied by Apple. But the new calibration system is really a calibration framework, a plug-in architecture which can easily accomodate third party calibration applications. Developers can simply write their own calibrators as plugins to the calibration framework, and when the user hits the "Calibrate" button, a list of all installed plugins comes up.
You change the monitor's display characteristics by selecting different profiles in the profile list. For example, create one profile with a target white point of D50 and a second profile with a target white point of 9300. In the profiles list (shown in the picture above), click on the D50 profile, then click on the 9300 profile. Notice the monitor changes its white point as you select first one profile, then the other. The same thing goes for different gammas. If you set the gamma to 1.8 for one profile and to 2.2 for another, when you select either in the list, the monitor's display changes to reflect the gamma setting in the profile.
If you have an AppleVision Display or a ColorSync Display, Apple’s software Default Calibrator will not be available for use, since these displays have their own built in hardware calibration systems separate from the new calibration framework. As a result, you won’t see the “Calibrate” button on these displays unless you’ve installed a third party calibrator which does take advantage of the framework.
So once you’ve created these profiles what do you do with them? You can use them to do ColorSync matching, using either AppleScripts, the ColorSync plug-ins for Photoshop, or ColorSync-aware third party applications.
AppleScript Support
Now you can use AppleScript to do the same kinds of ColorSync matching previously available only in the ColorSync Photoshop plug-ins or in third party applications. There are several sample scripts included with ColorSync 2.5, so you can cut, paste and modify parts of them for your own use. More documentation about each of the scripts can be found in the “Sample Scripts ReadMe” file.
This scriptability is the result of the ColorSync Extension being a faceless background application, as opposed to the simple extension ColorSync used to be. Now that it’s an application, it has its own AppleScript dictionary. You can examine this dictionary by finding “ColorSync Extension” in the extensions folder and dragging it onto the Script Editor, which is in the Apple Extras folder inside the AppleScript folder. Script Editor then brings up a window with all the commands the ColorSync Extension will respond to. It can embed, match, proof, link, and even quit. But don’t expect to see it in your processes list, because it’s faceless...it’s there, you just can’t see it.
Profile Cache File
ColorSync now makes use of a cache file in the Preferences folder to keep track of the currently installed profiles. Through a series of checks on the modification date of each profile, the modification dates of folders and subfolders, and the total number of profiles installed, ColorSync is able to quickly determine whether any profiles have been added or removed, passing this information on to applications requesting it. This can potentially speed up profile management routines such as building a list of profiles, displaying a pop-up menu of the available profiles, and so on.
New Profile Folder Location and Subfolders
Earlier versions of ColorSync searched in the “ColorSync™ Profiles” folder inside the Preferences folder for all installed profiles. Version 2.5 now places a “ColorSync Profiles” folder directly in the System Folder. This change was made so that users would not accidentally detete all their profiles if they deleted other preferences and, perhaps more importantly, so profiles can be automatically routed to the profiles folder in the next release of the MacOS. For backward compatibility, ColorSync creates an alias to the old “ColorSync™ Profiles” folder inside the new “ColorSync Profiles” folder.
A new feature of the “ColorSync Profiles” folder is that it now allows subfolders of profiles. For example you could organize your profiles folders as below:
Applications can (and should) call ColorSync to get the list of currently installed profiles, as opposed to assuming the path to the original folder. This is especially necessary to support the new subfolder feature. Previous versions of ColorSync only looked at profiles inside the Profiles Folder, but didn’t look inside subfolders. That’s fine if you only have a few profiles, but it’s nice to be able to organize your profiles into subfolders for clarity, especially if you have several dozen of them. Notice in the picture above that it’s okay to have subfolders, individual profiles, and aliases within the profiles folder
Photoshop Plug-ins
ColorSync 2.5 ships with new versions of the Photoshop plug-ins that shipped with ColorSync 2.1. They behave pretty much the same as the original plug-ins, but now take full advantage of the new features of ColorSync 2.5.
The Photoshop plug-ins are a great aid to understanding what ColorSync actually does. The ColorSync Filter is accessible from the normal “Filters” menu in Photoshop, while Export and Import are accessible from the “File” menu.
Using the ColorSync Filter to do a proof is probably the most instructional example. Open an RGB image, then run the ColorSync filter, selecting the “proof” tab. Select a monitor profile for the source, and the same monitor profile for the proof, but select a printer profile as the destination. You should be able to see the color difference between the original image and the proofed image. By the way, what you’re doing is simulating what that image would look like if it were printed on that printer. By selecting different printers as the destination, you can compare what the image would look like on each printer. See the “ColorSync Plug-ins ReadMe” file for detailed information on how the plug-ins work.
Multiprocessing Support
ColorSync 2.5 can now take advantage of multiprocessor machines when performing matching operations. The matching algorithms are optimized to take advantage of multiple processors with about 90% efficiency. It’s scalable too, so in the presence of four processors, a given operation will take about a fourth of the time required with a single processor.
However, in low memory conditions on systems with 16mb or less of installed memory, you may occasionally see a warning dialog appear saying “The MP library could not be completely initialized due to insufficient memory.” This is an artifact of the multiprocessing library itself and can safely be ignored if your machine only has one processor - if none of this sounds familiar, then chances are you’ve only got one processor. If you see the warning often, you may wish to avoid its appearance by removing the Multiprocessing extensions from your extension folder.
Support for 16 bit images
ColorSync 2.5 now supports matching to and from high-resolution images which use 16 bits per pixel. Most common RGB images use no more than 8 bits per channel (256 degrees of red, 256 degrees of green, 256 degrees of blue) which when combined result in 16,777,216 possible colors - that’s the “millions of colors” option you may have seen when setting the color depth of your monitor using the Control Strip. In comparison, a 16 bit image may describe up to 65,536 shades in each red, green, and blue channel, resulting in over 218 trillion possible color combinations.
What gets installed
Choosing the “Easy Install” option during installation installs the control panel “ColorSync” and the extension “ColorSync Extension” into the appropriate folders of your system folder, and also installs the following files into the “ColorSync Extras” folder of the “Apple Extras” folder of your hard disk:
- AppleScript Files: AutoMatch
- AppleScript Files: DropEmbed
- AppleScript Files: DropProof
- AppleScript Files: Match to CMYK
- AppleScript Files: PC to Mac Gamma
- AppleScript Files: Sample Scripts ReadMe
- ColorSync 2.5 ReadMe
The “Easy Install” also installs the following ColorSync Profiles into the “ColorSync Profiles” folder of the “System Folder” of your hard disk:
- Apple 12" RGB Standard - Generic CMYK Profile
- Apple 13" RGB Standard - Generic Lab Profile
- Apple 16" RGB Page-White - Generic RGB Profile
- Apple 16" RGB Standard - Generic XYZ Profile
- Apple 21" RGB Page-White - Mac Color Classic Standard
- Apple 21" RGB Standard - Mac Color Display Standard
- Apple Multiple Scan 14 - Macintosh LC520 Standard
- Apple Multiple Scan 15 - PowerBook 165C Standard
- Apple Multiple Scan 17 - 9300 - PowerBook 180C Standard
- Apple Multiple Scan 17 - D50 - PowerBook 2400 Standard
- Apple Multiple Scan 17 - D65 - PowerBook 270C Standard
- Apple Multiple Scan 1705 - PowerBook 3400
- Apple Multiple Scan 20 - 9300 - PowerBook 520C Standard
- Apple Multiple Scan 20 - D50 - PowerBook 540C Standard
- Apple Multiple Scan 20 - D65 - PowerBook G3
- Apple Performa Display - sRGB Profile
- Apple Performa Plus Display - Twentieth Anniversary Macintosh
- ColorSync Display - 9300
You may also perform a “Custom Install” of ColorSync 2.5, allowing you to install any or all of the following:
the Kodak CMM (into the extensions folder),
the ColorSync Plugins and Plugins ReadMe (into the ColorSync Extras folder),
the following additional ColorSync profiles (into the ColorSync Profiles folder):
- Color SW 1500 Pattern - CSW 6500 Coated
- Color SW 1500 Scatter - CSW 6500 Plain
- Color SW 2500 Pattern - CSW 6500 Specialty
- Color SW 2500 Pattern Best 1 - Color LW 12/600 PS Profile
- Color SW 2500 Pattern Best 2 - Color LW 12/660 PS Profile
- Color SW 2500 Scatter - Color OneScanner 600/27
- Color SW 2500 Scatter Best 1 - Color OneScanner 1200/30
- Color SW 2500 Scatter Best 2 - CS ColorMatch 3.01 SWOP Sf C
- 4/C Ctd.TRUMATCH/RIT/Profile80
Supported Configurations
All parts of ColorSync 2.5 will work on both PowerPC and 68K machines running System 7.6.1 or later. The only exception is that the calibration framework’s “Calibrate” button requires that the Monitors & Sound control panel be present. Monitors & Sound is not part of the Easy Install option in System 7.6.1 for 68K machines, so on these systems the “Calibrate” button may not be available.
However, it is possible to go ahead and install both the Monitors & Sound control panel and the SystemAV extension onto a 68K machine by performing a “Custom Install” with the System 7.6.1 Installer. Once those are in place, you’ll see the “Calibrate” button in the Monitors & Sound control panel.
