Shades of Gray
Try this out. Turn on Quick Mask mode—you don't need a selection to begin with. Type D to reset the foreground color to black, and then Option-Delete (Mac) or Alt-Backspace (Windows) to fill the Quick Mask. Now paint within the Quick Mask with 20% gray (you can use the Color Picker palette to choose grays). Then turn off Quick Mask mode and paint in the selected area with bright red. Now choose Select > Deselect, lower the opacity of the painting tool to 80%, and paint with bright red. Your reds should look exactly the same. That's how Photoshop makes a selection fade out—by simply lowering the opacity of the tool you are using. This can sometimes be confusing, though, because the marching ants show up only where an image is at least 50% selected. So, try this one on for size. Turn on Quick Mask mode and paint with 49% gray, and then paint in another area with 51% gray. Then go back to Standard mode and paint across the area. Only the areas that are at least 50% gray show up as marching ants, but the other areas are still selected, even though the marching ants don't show up in those areas (Figure 2.102). Now turn on Quick Mask mode, reset the foreground color by typing D, type Option-Delete (Mac) or Alt-Backspace (Windows) to fill the Quick Mask, and then paint with 55% gray. Now go back to Standard mode, and you'll get a warning message (Figure 2.103).
Figure 2.102. When painting in Quick Mask mode, only the areas that contain less than 50% gray will be visible when the selection is viewed as marching ants.
Figure 2.103. When you paint with shades brighter than 50% gray, a warning will appear when you go back to Standard mode.
We really haven't done anything fancy yet, so let's try something fun. To start with, you have to remember that when you work in Quick Mask mode, Photoshop treats the selection as if it is a grayscale image that you can paint on. That means you can use any tool that is available when working on grayscale images. So select an area using the Marquee tool, turn on Quick Mask mode, choose Filter > Distort > Ripple, and mess with the settings until you've created something that looks a little kooky (Figure 2.104). Finally, go back to Standard mode and see what you've got. You can create infinite varieties of fascinating selections with this simple technique.
Figure 2.104. Applying the Ripple filter in Quick Mask mode. (©2005 Stockbyte, www.stockbyte.com)
You can also convert a logo or sketch into a selection using Quick Mask mode. All you need to do is copy the image, turn on Quick Mask mode, choose Edit > Paste, and then choose Image > Adjustments > Invert (Figure 2.105). If the logo was in color, you might end up with shades of gray (which will look like shades of red in Quick Mask mode). In that case, you'll need to choose Image > Adjustments > Levels and pull in the upper-right and upper-left sliders until the image is pure black and pure white. Once everything looks right, turn off Quick Mask mode and you'll have your selection.
Figure 2.105. Adjusting a logo using the Levels dialog box.
Now let's figure out how to “unfeather” a selection using Quick Mask mode (Figure 2.106). Remember, a feathered edge looks like a blurry edge in Quick Mask mode. All you have to do to remove that blurry look is to then choose Image > Adjustments > Threshold. This will give the mask a very crisp, and therefore unfeathered, edge.
Figure 2.106. Unfeathering a selection using Threshold. Left: Original image. Center: Threshold setting used. Right: Result of applying Threshold.
