Photoshop CS Timesaving Techniques For Dummies [Electronic resources] نسخه متنی

Working with CMYK

Computer monitors display color by blending red, green, and blue light; this is called RGB color mode. You typically use RGB mode when working on projects in Photoshop. Printing presses create color by blending cyan, magenta, yellow, and black inks; this color mode is called CMYK. Because RGB mode and CMYK mode create color in such different ways — one uses lights in three colors, and the other uses inks in four colors — it’s very hard to convert colors exactly from RGB to CMYK and get the results that you want. However, Photoshop’s color manage- ment system helps with the conversion by letting you select standard printing setups, and proofing the settings by printing a color proof and matching it to the proof on-screen.

Here’s a checklist that you need to follow when working on a project that will end up as CMYK separations, ready for offset printing:

Make sure that your monitor is correctly calibrated. (See Technique 4.)





Convert your RGB image to CMYK color mode.





Call your commercial printer and get the custom CMYK settings for the printing press and paper type you’re using.

Different types of paper absorb ink in different ways, so the amount of ink used needs to be adjusted depending on the paper.






Enter the custom CMYK settings into Photoshop by using the Color Settings dialog box and choosing Edit>Color Settings/Photoshop> Color Settings.





Use the custom CMYK settings to soft proof your art, previewing how the image will look when printed as I describe in “Setting up soft proofing.”





Look at your image with Photoshop’s Out-of-Gamut feature, adjusting any colors that aren’t printable.





Use the Unsharp Mask to resharpen the image.

Take a look at Technique 37 for more information about the Unsharp Mask feature.





Soft proof again to be sure that the image looks just the way you want it.





Print a CMYK proof by using a high-end color PostScript printer, and then use a spectro-colorimeter (a machine that measures color values) to determine the exact colors in your image.

Commercial printers usually help you with this step. If any of the colors are off, readjust the Photoshop image, and then print and analyze another proof. (Using adjustment layers is a great way to make color corrections. Check out Technique 22 to find out more about adjustment layers.)





Using the Print Preview dialog box, set up the various printer’s marks that you need.

The printer’s marks include registration marks, crop marks, and a calibration bar (used for checking the colors). Check with your commercial printer to see which printer’s marks they recommend using.





If your commercial printer doesn’t accept Photoshop PSD files, create CMYK separations for your image saved in EPS format.

Phew! Some list, huh? The next six sections take you through these steps, showing you how to convert your image from RGB to CMYK, enter custom CMYK

printing press settings, set up soft proofing, check for unprintable colors, add the printer’s marks that you need, and then create CMYK separations. I know it sounds like a lot, but take it step by step and you discover that this isn’t so hard after all.

Entering and saving custom CMYK printer settings

Choosing custom CMYK settings gives you more control over the amount of ink coverage that a printing press uses when printing your project. You can get these custom settings from your commercial printer. Many times, the default settings that come with Photoshop (such as the U.S. Prepress Defaults) are good enough and the printer specifies them. Here’s how to set up custom CMYK settings:

Choose Edit>Color Settings/Photoshop> Color Settings.

The Color Settings dialog box opens, as shown in Figure 14-1, ready for you to select the prepress settings that you need.




Figure 14-1: The Color Settings dialog box is used to enter custom CMYK prepress settings.







In the Working Spaces area, use the CMYK drop-down list to select the prepress settings that you need. (See Figure 14-2.)




Figure 14-2: Select one of the prepress settings that matches the press and paper type that you’re using.


If you aren’t in the United States, select prepress settings based on your geographic location.

If one of the predefined prepress settings works for you, you do not need to create a custom CMYK setting, so skip to Step 9.





If you need to select custom settings, choose Custom from the CMYK drop-down list.

The Custom CMYK dialog box opens, as shown in Figure 14-3, giving you access to ink settings.




Figure 14-3: Use the Custom CMYK dialog box to select the amount of ink coverage.






Type a name for the custom CMYK settings in the Name text box.





Select an ink type from the Ink Colors drop-down list, and use the Dot Gain text box to enter the correct percentage.

This information should be supplied by your commercial printer.





In the Separation Options area, use the radio buttons and text boxes to select the proper settings.

The commercial printer should also provide these settings. In the Separation Options area, you can set the following:





Separation Type: Your options are GCR (Gray Component Replacement) or UCR (Undercolor Replacement). This setting tells Photoshop what type of printing press is being used.





Black Generation: This option sets how much black is used when your RGB image is converted into CMYK. This prevents the CMYK inks from becoming muddy when they’re mixed together.





Black Ink Limit, Total Ink Limit, and UCA Amount: Enter a percentage in each of these text boxes to set the amount of ink that’s used on each printing plate.







Click OK to close the Custom CMYK dialog box and return to the Color Settings dialog box.





Click Save, enter a name for the color settings in the Save dialog box that appears, and then click Save. (See Figure 14-4.)





Figure 14-4: Saving your custom CMYK color settings.


The Save dialog box closes and your custom-named CMYK settings appear selected in the CMYK drop-down list in the Working Spaces area of the Color Settings dialog box.





Click OK to close the Color Settings dialog box.

Great job! You’re on your way to using Photoshop to proof and create CMYK separations. The next step is to convert your image to CMYK color mode.

Checking for unprintable colors

Out-of-gamut (non-printable) colors are a problem when printing a project at a commercial press because they can lead to unexpected results.

When you convert an image from RGB mode to CMYK mode, any out-of-gamut RGB colors are forced into the printable CMYK color range. This can lead to unwanted color shifts.

So, before you convert to CMYK and soft proof your project, check for unprintable colors. Here’s how:

Choose View>Proof Setup>Working CMYK.





Choose View>Gamut Warning.

The non-printable colors in the image are covered with an opaque gray mask, as shown in Figure 14-5.




Figure 14-5: An opaque gray mask covers the out-of-gamut colors.








Tip

By default, out-of-gamut colors are shown using a medium gray mask. You can change the color and opacity of this mask by choosing Edit (Photoshop on a Mac)>Preferences> Transparency & Gamut, and then changing the settings in the Gamut Warning area of the Preferences dialog box.






Choose Select>Color Range.

This opens the Color Range dialog box shown in Figure 14-6.




Figure 14-6: Use the Color Range dialog box to select the out-of-gamut areas.






Use the Select drop-down list to select Out of Gamut, and then click OK.

All out-of-gamut areas in the image are selected, as shown in Figure 14-7. This protects the areas that contain printable colors and contains your work to the non-printable areas.




Figure 14-7: By selecting the out-of-gamut areas, the printable colors are protected from editing.






Select the Sponge tool from the Toolbox.





Select Desaturate from the Mode drop-down list on the Options bar.





Use the Flow slider bar to select a percentage.

Flow sets how quickly pixels are desaturated. A higher percentage desaturates an area faster than a lower percentage.





Use the Brush picker to select the diameter of the sponge.





Stroke across the selected, out-of-gamut areas.

When the color in an out-of-gamut area moves into printable colors, the gray mask disappears. Be careful when using the Sponge tool though: Too much desaturation can make colors dull.








Tip

Really zoom in on the areas that you’re desaturating so that you can see exactly when pixel colors move from out-of-gamut to printable.

Converting to CMYK color mode

This next step is a breeze. All that you need to do is choose Image>Mode>CMYK Color. When you

convert to CMYK mode, notice that CMYK appears in the title bar of your image next to the filename.

As the conversion occurs, you may also notice that the colors in the image become a bit dull-looking. This is because of the color shift that occurs when Photoshop converts the image from one color space to another. You can correct this shift by adjusting the tone using levels and curves. For more information about color correction, turn to Technique 30.

Setting up soft proofing

Soft proofing lets you see a pretty accurate preview of your image by using the default prepress settings or custom CMYK settings that you selected and saved in the earlier section, “Entering and saving custom CMYK printer settings.” To ensure that the image colors that you see while soft proofing are correct, you need to calibrate your monitor first. For directions on calibrating your monitor, turn to Technique 4.

Here’s how to set up soft proofing:

Choose View>Proof Setup>Custom.

The Proof Setup dialog box opens, as shown in Figure 14-8. This dialog box is used to select a custom CMYK color setting and how color is converted when your image moves from one color space (your monitor and Photoshop program) to another color space (the printing press).





Figure 14-8: The Proof Setup dialog box is used to select soft proofing options.






Make sure that the Profile drop-down list has the right prepress settings selected.

The default prepress or custom CMYK settings that you created in “Entering and saving custom CMYK settings” should already be selected. If the settings are not selected, use the drop-down list to find and select them.





Use the Intent drop-down list to select a color-conversion setting.

Your commercial printer should provide the setting. You have four options to choose from:





Perceptual: Converts color values in a way that produces little color shift. Good for photographs and other continuous-tone images.





Saturation: Converts color values with the intent of preserving vivid colors. This option can produce a noticeable color shift. Good for sharp-edged images, such as charts and graphs.





Relative Colorimetric: The default setting, this option converts color based on the monitor’s whitepoint setting. This option can produce a noticeable color shift.





Absolute Colorimetric: Converts color based on the printable color range (gamut), and attempts to convert colors that are out-of-gamut into printable colors. This can produce color shifts in non-continuous areas of the image, making for some unintended results.







Click Save, enter a name for the proof setup in the Save dialog box, and then click Save. (See Figure 14-9.)




Figure 14-9: Use the Save dialog box to enter a name for your custom soft proof settings.






Click OK to close the Proof Setup dialog box.







Tip

The soft proof settings that you saved are now available at the bottom of the View> Proof Setup menu.






Choose Proof>View Colors or press Ctrl+Y/z +Y to turn on soft proofing.

When soft proofing is turned on, notice that the selected proof setting name appears in the title bar of the image window, as shown in Figure 14-10.




Figure 14-10: The selected soft proof setting appears in the image’s title bar.








Tip

If your project contains several images that you want to soft proof by using the same custom proof settings, you need to turn on soft proofing and select the settings for each image.

Adding printer’s marks

Depending on your project, you may need to use various printer’s marks. For instance, if your project — suppose it’s a brochure — uses four ink colors (this would be called a 4-color or 4-c job), you would need to include registration marks so that the pressman could exactly align the printing plates on the press. A calibration bar would be needed to measure colors exactly. The edges of the brochure and any folds would need to be indicated with crop marks. Figure 14-11 shows some typical printer’s marks.

Figure 14-11: Printer’s marks tell the pressman and other workers at the printing company how to align, calibrate, trim, and fold your project.

Using the Print dialog box, you can quickly add printer’s marks to any image. Here’s how:

Choose File>Print with Preview or press Alt+Ctrl+P/Option+z +P.

The Print dialog box opens, as shown in Figure 14-12, and displays the image in the Preview Pane.




Figure 14-12: Use the Print dialog box to set up printer’s marks.






Select the Show More Options check box.

As shown in Figure 14-13, the Print dialog box expands to display more available settings.




Figure 14-13: Click Show More Options to see added options in the Print dialog box.






Use the drop-down list below the Show More Options check box to select Output.





Use the various check boxes to select the printer’s marks that you need.

You can select from calibration bars, registration marks, corner and/or center crop marks, description, and labels.

As you select the various printer’s marks, they appear around the image in the Preview pane.





When you’re finished selecting printer’s marks, click Done.

Saving your image as an EPS file

Depending on the commercial printer that you’re using, you may not need to save your image as an EPS file. Many printers will take it from here and accept a Photoshop PSD file. But, if your printer doesn’t have access to Photoshop and needs your image in EPS file format, this section tells you all you need to know.

When saving your image in EPS format, you actually want to save a copy of the image. This protects your original image file, in case you need to edit the image in the future.

Check with your commercial printer for the settings that you need to use when saving your image files in EPS format.

With your CMYK image open, choose File> Save As.

The Save As dialog box opens, as shown in Figure 14-14.





Type a name for the image in the File Name (Windows) or Save As (Mac) text box.




Figure 14-14: Use the Save As dialog box to save a copy of your image in EPS file format.






Use the Format drop-down list to select Photoshop EPS (*.EPS).





Select the As a Copy check box.





Select the Use Proof Setup and Embed Color profile check boxes.

This ensures that your image is saved with the custom CMYK settings that you created in the section “Entering and saving custom CMYK printer settings,” earlier in this chapter.





Click Save.

The EPS Options dialog box opens, as shown in Figure 14-15.




Figure 14-15: The EPS Options dialog box is used to set how the file is saved.






Select an option from the Preview drop-down list.

If you choose a 1 bit/pixel option, the file is saved with a black and white preview. The 8 bits/pixel option saves the file with a color preview.





Use the Encoding drop-down list to select how the image file data is saved.

Binary is a good default option to select because it doesn’t lose any image data. Some printers, however, cannot use binary encoded data. If this is the case, select ASCII85. Ask your commercial printer which option is the best one to use.





Click OK.

Photoshop saves your image in EPS format.