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This chapter is from the book

This chapter is from the book

Understanding How to Choose Transparency & Gamut Settings

It's funny, but the correct choice on the Transparency & Gamut page of the Preferences dialog box depends entirely on the color content of the image at hand. Figure 3.8 shows the Transparency & Gamut Preferences page. Transparency settings determine what the pattern is for areas that are transparent. In other words, a large pink and black checkerboard could be used to denote transparent regions in an image; so could small gray-on-white checkerboard patterns. The option is yours to make. Gamut (actually, "out of gamut") tells you where in an image the color threshold has been exceeded. In PlainSpeak, if an area is out of gamut, it contains color or a percentage of color that cannot be reproduced on paper.

Figure 3.8Figure 3.8 The Transparency & Gamut page of the Preferences dialog box.

The default Transparency Grid Colors setting is Light checkered. But, what if the image area you are editing has a light checker pattern to it? As you can see at the top of Figure 3.9, in that situation, the transparency default is about as worthwhile as going to sea in a tea strainer.


The Video Alpha setting The Use Video Alpha option will probably interest only a small percentage of Photoshop users. If your video board enables images to be laid on top of a live video signal and you will be working with video in Photoshop, place a check in the Use Video Alpha box.

As far as the Gamut Warning color goes, if you want Photoshop to display a tinted overlay in areas in your image that cannot be faithfully reproduced in CMYK colors, you would usually press Ctrl()+Shift+Y or choose View, Gamut Warning. The default for this is gray at 100% opacity. So here's the obvious question now: How can you tell whether something's out of gamut if the original picture contains a lot of grays, as shown in Figure 3.9?

Figure 3.9Figure 3.9 You must choose—and rechoose—colors for CMYK gamut saturation and for transparency design, depending on the specific image you are editing.

The default checkerboard transparency pattern does a fairly good job at helping you to determine the location of opaque pixels in the image. But you will inevitably run into situations in which a solid color does a better job at showing the transparent areas.

In the following set of steps, we'll demonstrate the problem of using a transparency color that is too close to the colors in the image and then show you how to fix it using four keystrokes:

Changing Transparency Display

  1. Open the visible.psd image from the Examples\Chap03 folder on the companion CD. Zoom to the word visible in the image to do the editing.

  2. Display the Layers palette by pressing F7 if necessary, and click on the Add Layer Mask icon (the icon is a circle within a rectangle, to the right of the f icon) on the bottom of the Layers palette.

  3. Choose the Brush tool, choose the 20-pixel tip from the Options bar, and press D (default colors). If necessary, press X to make black the foreground color. Make sure Opacity is set to 100%, and then start hiding the image background by painting over it. Carefully work your way to the edge of the v in visible. Stop when you think you've trimmed around the outside edge of the v to see what you are supposed to be masking (see Figure 3.10). It's very hard to tell where the transparent background ends and the graphic begins, isn't it?

  4. Figure 3.10Figure 3.10 Add a layer mask, and then start painting around the v to remove the background.

  5. Press Ctrl(Command)+K, click the top drop-down list in the Preferences dialog box, and choose Transparency & Gamut.

  6. Click on the foreground color swatch, choose green from the Color Picker, click on OK, and then click on the other swatch for the grid and make it the same color green, as shown in Figure 3.11. Click on OK to apply the changes.

  7. Use the Zoom tool and zoom in to the area you are editing to 500%. Hold the spacebar and drag in the window until you see the area where you were editing, if needed (see Figure 3.12).

  8. Figure 3.11Figure 3.11 If you want a good view of the edges to mask in this image, choose a color not found in the image—a strong green.

    Wow! There are unedited areas you didn't even see, aren't there? However, now that you've defined a different color transparency grid, you can accurately trim around the lettering. The Polygon Lasso tool helps you work around the straight edges.

    The point's been made here, so you really don't need to completely edit around the lettering. But if you want the experience of working with the Brush tool, choose a tip that is two sizes smaller for going around the lettering. When the white background is completely gone, right-click (Macintosh: hold Ctrl and click) on the layer mask thumbnail, and choose Apply Layer Mask. For those of you who would like to return the swatches back to the default checkerboard colors in the Transparency & Gamut page, simply return to the dialog box, and use white for the first swatch (RGB values set to 255 each) and a pale gray for the second swatch (RGB values set to 203 each).

  9. You can save visible.psd to your hard disk, or simply close it without saving. Keep Photoshop open.

Figure 3.12Figure 3.12 Well, oops. Your view of both the transparent regions and the foreground design are important to perform accurate masking.

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