Out of Gamut: Photoshop, Previsualization, and Print Prediction

Bruce Fraser

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Printing from Photoshop
Photoshop also offers the ability to make conversions on the data it sends to the printer. If your printer is a printing press, these features probably aren’t useful to you, but if you’re printing to a desktop printer, they can be very useful indeed. Photoshop adds to each printer driver radio buttons that let you choose the Source Space, and menus that let you choose the Print Space and Rendering Intent (see figure 6). These same controls are replicated in the Print Options dialog box — any changes you make in one are carried over to the other.

Figure 6: Photoshop’s color management controls as they appear in a QuickDraw driver (top) and a Postscript driver (bottom).

But placing these controls in the printer driver has created a fair bit of confusion. The key thing to realize is that they don’t control the printer: Instead, they control the data that Photoshop sends to the printer. Since many printer drivers also offer color management features, the number of possible ways to print from Photoshop can be very large. Unfortunately, it also means that many of these ways will be incorrect. You need to decide whether you want Photoshop to do the color management, or the printer driver to do the color management, because if they both try to do the color management, you’ll get a double correction that usually produces pretty hideous results.

So, with the clear understanding that the buttons and menus control Photoshop’s behavior, not that of the printer driver, here’s what they do:

The Source Space radio buttons let you choose between Document and Proof Setup. If you choose Document as the source, Photoshop uses the unaltered values in the image, along with the profile that describes their color meaning, as the source for any conversion you define in the Print Space Profile menu. Let’s set the Proof Setup option aside for now.

There are really only three rational choices you can make in the Print Space Profile menu:

1. The profile for the printer, paper and ink to which you’re actually printing.
2. Same As Source.
3. Printer Color Management (PostScript Color Management when you print to a PostScript printer.

When you choose a specific profile in Print Space, Photoshop converts the image from the Source Space to the profile you’ve selected, using the rendering intent you select from the Print Space Intent menu. This is usually the most effective method of printing when you have a paper-specific printer profile available, but as previously noted, you must make sure that any color conversions are turned off in the printer driver.

When you choose Same as Source, Photoshop simply sends the source image data unchanged to the printer driver. I only use this option when I’m printing profiling targets, where the numbers in the file are all that matters, or when I’ve already converted the image to the printer’s space.

Printer/PostScript Color Management also sends the data unchanged to the printer driver, but also includes the profile that describes the source space so that the printer driver’s color management can interpret it correctly. This is the only option that works reliably when printing from Windows systems to printers that have a single profile that covers all media, such as most Epson printers (see sidebar “Canned Profiles, Custom Profiles, and Pretend Profiles“). If you use this option, you must, of course, turn on the ICM color management features in the printer driver. If you have custom profiles, this limitation doesn’t apply. (The same approach also works with ColorSync print matching in the driver on the Mac, but since most Mac printer drivers include real profiles for each supported paper stock, I prefer to let Photoshop do the color matching.)

The Proof is in the Printing
If you choose Proof Setup as the Source Space, Photoshop executes the conversion you’ve simulated in Proof Setup before passing the data to the Print Space conversion. The main use of Proof Setup as source is to let you produce proofs of another printing process without actually converting your source data. For example, if you’re working on an RGB image that will eventually be printed on a SWOP press, you can set Proof Setup to provide an on-screen simulation of the SWOP press print. If you then want to proof that SWOP press print on a desktop printer, you can choose Proof Setup as the source space, and Photoshop will then convert the print data to the SWOP press space, using the rendering intent you defined in Proof Setup, before it makes the conversion to your desktop printer’s space.

If you’ve set Proof Setup to simulate the desktop printer you’re actually printing to, choosing Proof Setup as the source space might seem to invite the danger of a double correction. In fact, it doesn’t matter, but only because Photoshop is smart enough to recognize that when a source and a target profile are the same, no conversion is necessary. It’s probably a good habit to avoid specifying Proof Setup as the source space unless you really want your desktop printer to emulate some other printing process, because other software may not be as smart as Photoshop, and double conversions are a frequent source of color management trouble.

Obviously, there are many other possible combinations of settings in both Proof Setup and Print. Unless you fully understand both what you’re trying to do, and exactly how these settings will help you do it, my advice is to stick to the options I’ve outlined here. If you do so, the only limitation on the accuracy of your output will be the accuracy of your profiles.

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