Real World Adobe® Photoshop® CS2 [Electronic resources] : Industrial-Strength Production Techniques نسخه متنی

Soft-Proofing Controls

If you''''re sane, you probably want to get some sense of what your images are going to look like before you commit to the $50,000 print run. There are three ways to proof your pictures: traditionally (print film negatives and create a laminated proof like a Matchprint), on a color printer (like one of the new breed of inkjet printers), or on screen. On screen? If you''''ve been paying attention during this chapter, you know that you can set up your system well enough to start really trusting what you see on screen. Proofing images on screen is called soft-proofing, and Photoshop CS2 offers soft-proofing capabilities whose accuracy is limited only by the accuracy of the profiles involved.

In Photoshop CS2, soft-proofing has its own set of controls, separate from the Color Settings dialog box. These allow you to preview your output accurately, whether it''''s RGB or CMYK. This is a huge advantage for those of us who print to RGB devices like film recorders or to those photorealistic inkjet printers that pretend so assiduously to be RGB devices that we''''re forced to treat them as such. But soft-proofing is a big improvement for those of us who print CMYK too, because we can soft-proof different conversions to CMYK while we''''re still working in RGB, and have them accurately depicted on screen. (For example, you can quickly see how the same image would look on newsprint and in your glossy brochure.)

The Proof Colors command on the View menu lets you turn soft-proofing on and off. It even has the same keyboard shortcut, Command-Y, as the old CMYK Preview it replaces. But the real magic is in the Proof Setup submenu, which governs exactly what Proof Colors shows you (see Figure 5-29). The settings you make in Proof Setup are specific to the image window that''''s in the foreground when you make the settings, not to the image itself. This means that you can create several views of the same image (by choosing New View from the View menu), and apply different soft-proofing settings to each view, letting you see how the image will work in different output scenarios.

The default setting for Proof Colors (what you get if you don''''t change anything in the Proof Setup dialog box) works as follows:

It first simulates the conversion from the document''''s space to working CMYK, using the rendering Intent and Black Point Compensation settings specified in Color Settings.

It renders that simulation to the monitor using relative colorimetric rendering. If Black Point Compensation is turned on in Color Settings, it''''s also applied to the rendering from the proof space to the monitor.

This essentially duplicates the behavior of the old CMYK Preview, except that it''''s a bit more accurate (because it doesn''''t use an intermediate transformation from CMYK to working RGB; instead, it goes straight from working CMYK to the monitor).

However, to really unleash the power of the new soft-proofing features, you need to visit the Proof Setup dialog box, which gives you an unprecedented degree of control over your soft proofs.

Proof Setup Dialog Box

Proof Setup lets you independently control the rendering from the document''''s space to the proof space, and from the proof space to the screen. Ultimately, it allows you to preview accurately just about any conceivable kind of output for which you have a profile. You can open the Customize Proof Condition dialog box by choosing Custom from the Proof Setup submenu (under the View menu; see Figure 5-30).

Custom Proof Condition

The Custom Proof Condition menu lets you recall setups that you''''ve saved in the special Proofing folder. (On Mac OS X, this is the Library/Applications Support/Adobe/Color/Proofing folder. In Windows, it''''s in the Program Files/Common Files/Adobe/Color/Proofing folder.) You can save proof setups anywhere on your hard disk by clicking Save, and load them by clicking the Load button, but the setups you save in the Proofing folder appear on the list automatically. (Even better, they also appear at the bottom of the Proof Setup submenu, where you can choose them directly.)

Device to Simulate

The Device to Simulate menu lets you specify the proofing space you want to simulate. You can choose any profile, but if you choose an input profile (for a scanner or digital camera), the Preserve Color Numbers checkbox becomes checked and dimmed, and all the other controls become unavailable. (We''''re not sure why you would choose an input profile, but we suppose it''''s nice to have the option.) Generally, you''''ll want to choose an RGB, CMYK, or grayscale output profile.

Preserve RGB/CMYK/Gray Numbers

The Preserve Numbers checkbox, when on, tells Photoshop to show you what your file would look like if you sent it to the output device without performing a color space conversion. It''''s available only when the image is in the same color mode as the selected profile (as when both are in RGB); when you turn it on, the Intent menu becomes unavailable, since no conversion is requested.

We''''ve found that this feature is particularly useful when you have a CMYK file that was prepared for some other printing process. It shows you how the CMYK data will work on your output, which can help you decide whether you need to edit the image, convert it to a different CMYK space, or just send it as is. It''''s also useful for seeing just how crummy your image will look if you send it to your desktop inkjet printer without converting it to the proper profile (see "Converting at Print Time," later in this chapter).

Rendering Intent

The Rendering Intent popup menu lets you specify the rendering intent you want to use in the conversion from the document''''s space to the proof space. This is particularly useful for helping you decide whether a given image would be better served by perceptual or relative colorimetric rendering to the output space. It defaults to the Color Settings default rendering intent until you change it, whereupon it remembers what you last used. However, when you save a proof setup, your selected rendering intent is saved with it; so, if you find that you''''re continually being tripped up by the wrong intent, you can just save a proof setup with your preferred rendering intent.

Black Point Compensation

The Black Point Compensation checkbox lets you choose whether or not to use black point compensation in the conversion from the document''''s space to the proof space. You almost invariably want to keep this turned on, but you can always uncheck it and see the effect to make sure.

Display Options (On-Screen)

The checkboxes in the Display Options sectionSimulate Paper Color and Simulate Black Inkcontrol the rendering of the image from the proofing space to the monitor. When both Simulate Paper Color and Simulate Black Ink are turned off, Photoshop does a relative colorimetric rendering (with black point compensation if that option is turned on in Color Settings). This rendering maps paper white to monitor white and ink black to monitor black, using the entire dynamic range of the monitor. If you''''re using a generic monitor profile, this is probably as good as you''''ll get (of course, with a canned monitor profile, you can''''t trust anything you see on screen anyway). With a good monitor profile, though, you should check out the alternatives.

When you turn on Simulate Black Ink, it turns off black point compensation in the rendering from proof space to the monitor. As a result, the black you see on the monitor is the actual black you''''ll get on output. (Within limitsmost monitor profiles have a "black hole" black point. The black ink simulation will be off by the amount that real monitor black differs from the monitor profile''''s black point. On a well-calibrated monitor, the inaccuracy is very slight.) If you''''re printing to a low-dynamic-range process like newsprint, or inkjet on uncoated paper, Simulate Black Ink will give you a much better idea of the actual blacks you''''ll get in print.

Turning on the Simulate Paper Color checkbox makes Photoshop do an absolute colorimetric rendering from the proof space to the display. (Simulate Black Ink becomes checked and dimmed, since black point compensation is always disabled in absolute colorimetric conversions.) In theory at least, turning on Simulate Paper Color should give you the most accurate soft-proof possible.

In practice, the most obvious effect of turning on Paper White isn''''t that it simulates the color of the paper, but rather that you see the compressed dynamic range of print. If you look at the image while turning on Simulate Paper Color, the effect is dramaticso much so that Bruce looks away from the monitor when he turns on Simulate Paper Color, and waits a few seconds before looking at the image to allow his eyes to adapt to the new white point. More importantly, he also makes sure that he hides all white user interface elements, so that his eyes can adapt.

Obviously the quality of the soft-proofing simulation depends on the accuracy of your monitor calibration and on the quality of your profiles. But we believe that the relationship between the image on screen and the final printed output is, like all proofing relationships, one that you must learn. We''''ve never seen a proofing system short of an actual press proof that really matches the final printed piecelaminated film proofs, for example, often show greater contrast than the press sheet, and may have a slight color cast too, but most people in the print industry have learned to discount the slight differences between proof and finished piece.

It''''s also worth bearing in mind the limitations of the color science on which the whole ICC color management effort is based. We still have a great deal to learn about color perception, and while the science we have works surprisingly well in many situations, it''''s only a model (see the sidebar "CIE Limitations and Soft Proofing"). The bottom line is that each of the different soft-proofing renderings to the monitor can tell you something about your printed images. We recommend that you experiment with the settings and learn what works for you and what doesn''''t.

Proof Setup Submenu

The Proof Setup submenu (under the View menu) contains several other useful commands that we should discuss. For instance, when you''''re viewing an RGB or grayscale image, you can view the individual CMYK plates (or the CMY progressive) you''''d get if you converted to CMYK via the Mode submenu (in the Image menu). You can also use these commands to view the individual plates in CMYK files, but it''''s much faster and easier to use the keyboard shortcuts to display individual channels, or click on the eyeballs in the Channels palette.