Inks, separations, and screen frequency

The Ink Manager provides control over inks at output time. Changes you make using the Ink Manager affect the output, not how the colors are defined in the document.

Ink Manager options are especially useful for print service providers. For example, if a process job includes a spot color, a service provider can open the document and change the spot color to the equivalent CMYK process color. If a document contains two similar spot colors when only one is required, or if the same spot color has two different names, a service provider can map the two to a single alias.

In a trapping workflow, the Ink Manager lets you set the ink density for controlling when trapping takes place, and it lets you set the correct number and sequence of inks.

Do one of the following:

• From the Separations Preview panel menu (Window > Output > Separations Preview), choose Ink Manager.
• Choose File > Print, and click Output. In the Output section, click Ink Manager.

Each separation is labeled with the color name that InDesign assigned it. If an icon of a printer appears next to the color name, InDesign creates a separation for the color. Any spot inks—including those defined and used in imported PDF files or EPS graphics—also appear in the ink list.

Using the Ink Manager, you can convert spot colors to process colors. When spot colors are converted to process color equivalents, they are printed as separations rather than on a single plate. Converting a spot color is useful if you’ve accidentally added a spot color to a process color document, or if the document contains more spot colors than are practical to print.

You can map a spot color to a different spot or process color by creating an alias. An alias is useful if a document contains two similar spot colors when only one is required, or if it contains too many spot colors. You can see the effects of ink aliasing in the printed output, and you see the effects on‑screen if Overprint Preview mode is on.

Some predefined spot colors, such as colors from the TOYO, PANTONE, DIC, and HKS libraries, are defined using Lab values. For backward compatibility with previous versions of InDesign, colors from these libraries also include CMYK definitions. Lab values, when used in conjunction with the correct device profiles, give you the most accurate output across all devices. If color management is critical to your project, you might prefer to display, export, and print spot colors using their Lab values. The Ink Manager option Use Standard Lab Values For Spots lets you control which color mode InDesign uses for these predefined spot colors: Lab or CMYK. If you need the output to match earlier versions of InDesign, you should use the CMYK equivalent values.

In commercial printing, continuous tone is simulated by dots (called halftone dots) printed in rows (called lines or line screens). Lines are printed at different angles to make the rows less noticeable. The Screening menu in the Output section of the Print dialog box displays the recommended sets of line screens in lines per inch (lpi), and resolution in dots per inch (dpi), based on the currently selected PPD. As you select inks in the ink list, the values in the Frequency and Angle boxes change, showing you the halftone screen frequency and angle for that ink.

A high line-screen ruling (for example, 150 lpi) spaces the dots closely together to create a finely rendered image on the press; a low line-screen ruling (60 lpi to 85 lpi) spaces the dots farther apart to create a coarser image. The size of the dots is also determined by the line screen. A high line-screen ruling uses small dots; a low line-screen ruling uses large dots. The most important factor in choosing a line-screen ruling is the type of printing press your job will use. Ask your service provider how fine a line screen its press can hold, and make your choices accordingly.

The PPD files for high-resolution imagesetters offer a wide range of possible screen frequencies, paired with various imagesetter resolutions. The PPD files for low-resolution printers typically have only a few choices for line screens, usually coarser screens of between 53 lpi and 85 lpi. The coarser screens, however, give optimum results on low‑resolution printers. Using a finer screen of 100 lpi, for example, actually decreases the quality of your image when you use a low-resolution printer for final output.

Depending on the type of printing press used and how information is transferred from the film to the printing plates, you may need to give your service provider film negatives or positives, with emulsion side up or down. Emulsion refers to the photosensitive layer on a piece of film or paper. Typically, print service providers require negative film in the United States and positive film in Europe and Japan. Check with your service provider to determine which emulsion direction they prefer.

To tell whether you are looking at the emulsion side or the nonemulsion side (also referred to as the base), examine the final film under a good light. One side appears shinier than the other. The dull side is the emulsion side; the shiny side is the base.

The Summary area of the Print dialog box displays a summary of color management information, printer’s marks dimensions, and bleeds for the document. The section also indicates whether trapping has been enabled.

You can also perform a quality check before printing or handing off the document to a service provider.

Create a hard proof to verify that colors will print on the correct separations, or a soft proof to preview how your document’s colors will look when reproduced on a particular output device.

The hard proof represents your expectation of the way the final separations will appear, and helps the service provider to verify that the output is correct. Be sure to print proofs on a PostScript printer; you cannot reliably proof color separations printed from a non-PostScript printer.

To produce in‑RIP separations, you need the following software and hardware:

• A PPD file that supports in‑RIP separations.

• Any PostScript 3 output device, or a PostScript Level 2 device whose RIP supports in‑RIP separations. If the document contains duotones from Photoshop 5.0 or later, a PostScript 3 device is required to generate in‑RIP separations.