HI–FI COLOR

HI–FI FORMATS IN SOFTRIP

DCS 2.0
The DCS 2.0 image file format was defined by Quark in 1995 as a way to exchange color separations. This format is supported by Wasatch SoftRIP. A DCS 2.0 file normally appears as a file with the extension ".eps". All separation plates may be contained within that file, or it may contain references to additional files that must be present for the data to be complete. In any case, it is not an ordinary EPS (Encapsulated PostScript) file, in spite of its extension.

A DCS file commonly contains a composite color image intended for screen previews, along with some number of 'plates' that make up the separation. Wasatch SoftRIP provides some special controls that can be accessed by selecting DCS2 and Image Format tab from the Preferences menu (Illustration 1). If a DCS 2.0 file is opened by Wasatch SoftRIP with no special setting, the composite image is displayed. Illustration 2 is an example of the composite image displayed for a DCS 2.0 file created by QuarkXPress™.

Illustration 1: DCS, PSD, and TIFF Controls

In order to access the individual plates in this file with Wasatch SoftRIP, special settings must be made by selecting DCS2 and Image Format Options from the Options menu on the main window, and setting the controls as shown here in Illustration 1.

Illustration 2: Combined plates

When the same (four color) DCS file is opened with these settings, four pages will be RIP'd, as shown in Illustrations 3–6.

Illustration 3: Cyan plate

Illustration 4: Magenta plate

Illustration 5: Yellow plate

Illustration 6: Black plate

This is the setting that would normally be used for printing color separations with Wasatch SoftRIP.

Notice that these plates contain colors that overlap, and that will create new colors when the separations are printed, but also notice that this is not reflected in the composite image that is provided by Quark in the DCS file.

This is a fundamental problem with the way the DCS format is used in typical workflows—the overprints or traps are not shown by the composite. In order to see this with Wasatch SoftRIP, check Recombine Separations and reopen the file. You'll then see the image shown in Illustration 7.

Illustration 7: Recombined plates

Wasatch SoftRIP produces this image by separately RIP'ing the plates, and then recombining them prior to passing them through ICC color management. Because they are recombined before passing through color management, it is possible to construct color configurations that will allow accurate proofing of how the plates will print on press.

Hi–Fi Color with DCS 2.0 Files
When a DCS 2.0 file containing four plates is recombined, the color image is processed as a CMYK image through SoftRIP's normal ICC based color management.

When a DCS 2.0 file containing more than four channels is opened for a print mode that also has more than four channels (a Hi–Fi printer), most Wasatch color management is bypassed. Each plate of the DCS 2.0 file is routed directly to the calibration curves for that channel. Only the first four channels are re–sequenced by PlateColor comments, the rest of the channels go straight to the associate calibration curves and print heads.

This direct pass–through allows Hi–Fi color management to be performed completely upstream of Wasatch SoftRIP. It also allows for the direct creation of Hi–Fi color profiles by ICC color profiling packages with such capabilities, such as Gretag ProfileMaker and Monaco Color.

Problems with PlateColor Identification
Quark's specification requires that each plate in a DCS2.0 file be identified by a 'PlateColor' comment, but it does not specify what names should be used in those comments. It is most common to find the first four plates of the file identified by 'Black', 'Cyan', 'Magenta', and 'Yellow', but it is common to see other color names, often in other languages. We've seen an amazing and entirely unpredictable variety of color names in these 'PlateColor' comments.

When Wasatch SoftRIP can't identify the first four plates from the 'PlateColor' comments, it is common to have problems with swapping of the color channels. To reduce this problem, advanced users of Wasatch SoftRIP may wish to use a text editor such as 'notepad' to edit the file '/wwrip/plateident'. This file can include an unlimited number of lines. Each line that begins with one of the letters C, M, Y, or K designates a PlateColor comment that will be interpreted as, respectively, cyan, magenta, yellow, or black. The first letter must be followed by a space, and whatever follows is the PlateColor comment that will be interpreted.

Problems in this area can often be diagnosed by looking at 'Info' on Wasatch SoftRIP's main menu after opening a DCS2.0 file. The 'PlateColor' comments contained in the current file can be seen there.

TIFF and PSD
The remaining controls in Illustration 1 are provided to increase the flexibility of the Hi–Fi version of the TTFF and PSD (Photoshop) file formats. They are necessary because of ambiguity in the way these files are produced by various different application programs.

For normal RGB, Lab, or CMYK workflows, select Process Extra Channels as Alpha Channels (ignore). This is important to ensure that alpha channels are not interpreted as Hi–Fi inks.

To support Hi–Fi workflows where image files are expected to contain more than four color channels, select Process Extra Channels as Hi–Fi Color Channels.

When a Hi–Fi file containing more than four channels is opened for a print mode that also has more than four channels (a Hi–Fi printer), most Wasatch color management is bypassed. Each channel of the file is routed directly to the calibration curves for that channel.