|Color Management in Photoshop 5.x
The CMYK Setup dialog box lets you define the working space for CMYK files in three ways: Built-in, ICC, and Tables.
If you plan to convert your images to CMYK, Photoshop's traditional conversion controls are still available in the Built-in option (the default CMYK Setup option in Photoshop 5.x). This model uses the information from the Ink Options and Separation Options dialog boxes to create the color table used to perform the conversion.
The Built-in model in the CMYK Setup dialog box combines two traditional color settings from previous versions of Photoshop: Printing Inks Setup and Separation Setup.
Photoshop 5.x's CMYK Setup dialog box also includes some features not available in previous versions. Dot Gain can now be specified as Standard, meaning the same amount for all four inks (the default is the SWOP specification of 20% dot gain), or as individual Dot Gain Curves where measured values can be plotted at several points on the curve for each ink.
Dot Gain Curves menu (above) and dialog box (below)
|Note: Dot gain values are encoded differently in Photoshop 5.x than in Photoshop 4.0. You cannot get the same dot gain in Photoshop 5.x by simply using the 4.0 values.
Custom Inks can be specified by their CIE LAB coordinate values as well as by CIE xyY values. Spectrophotometers deliver spectral color information in a number of color coordinate system values.
Ink Colors dialog Box
The Estimate Overprints option incorporates what used to be a clever workaround to define the display of custom ink colors for spot color images using CMYK channels. It tells Photoshop 5.x to use the same math it uses in the Duotone Options dialog box to define what a customized CM (ie, Blue), CY (ie, Green), MY (ie, Red), and CMY will look like. For example, if you have redefined C, M, and Y using spot colors (such as Pantone), selecting Estimate Overprints calculates how they will display when combined with each other.
If you select the ICC option, you define the CMYK space by choosing a device profile, a render intent, and a color engine to perform the conversion. Photoshop has taken advantage of the ICC's open framework to allow color engines (also known as Color Management Models, or CMMs) other than the default color engine model to perform color conversions. In fact, Photoshop 5.x introduces its own CMM (Built-in), and uses that as its default color engine. This is also the same CMM used in InDesign and Illustrator 8.x. If you have installed other third-party CMMs (e.g., Kodak, Agfa, or Heidelberg) into your color management system, they will be available from the Engine menu.
CMYK Setup/ICC Engine and Intent menus
By selecting the Tables option, you can load separation tables from other applications, or click Save to convert your current settings to an ICC profile. This is extremely handy for working with legacy files (files created with Photoshop 4.0 or earlier).
CMYK Setup: Tables
In Photoshop 5.x, when you save a separation table from the Tables model of CMYK Setup, you are saving an ICC profile. This allows you to use Photoshop's traditional CMYK Setup calibration routine to define a profile for your printer. If the profile that ships with your printer does not give satisfactory results, you can use Photoshop to generate a profile that is satisfactory.