STEPS: Creating and Using an Edge Mask

1. Duplicate one of the color channels. Bring up the Channels palette and drag one of the color channels onto the little page icon. Ike is a grayscale image, so I duplicate the one and only channel.

2. Choose Filter ^ Stylize^ Find Edges. As I explain in Chapter 11, the Find Edges filter automatically traces the edges of your image with thick, gooey outlines that are ideal for creating edge masks.

3. Press Ctrl+I. Or choose Image ^ Adjust^ Invert. Find Edges produces black lines against a white background, but in order to select your edges, you need white lines against a black background. The Invert command reverses the lights and darks in the mask, as in the first example in Figure 10-15.

Figure 10-15: I copy a channel, find the edges, and invert (left). I then apply a string of filters to expand and soften the edges (middle). After converting the mask to a selection outline, I reapply Unsharp Mask with winning results (right).

Find edge mask

Figure 10-15: I copy a channel, find the edges, and invert (left). I then apply a string of filters to expand and soften the edges (middle). After converting the mask to a selection outline, I reapply Unsharp Mask with winning results (right).

4. Choose Filter ^ Noise ^ Median. You need fat, gooey edges, and the current ones are a bit tenuous. To firm up the edges, choose the Median filter, enter a value of 2 (or thereabouts), and press Enter.

5. Choose Filter ^ Other ^Maximum. The next step is to thicken up the edges. The Maximum filter expands the white areas in the image, serving much the same function in a mask as Select ^ Modify ^ Expand serves when editing a selection outline. Enter 4 for the Radius value and press Enter.

6. Choose Filter ^ Blur ^ Gaussian Blur. Unfortunately, the Maximum filter results in a bunch of little squares that don't do much for our cause. You can merge the squares into a seamless line by choosing the Gaussian Blur command and entering 4, the same radius you entered for Maximum. Then press Enter.

The completed mask is pictured in the second example of Figure 10-15. Though hardly an impressive sight to the uninitiated eye, you're looking at the perfect edge mask — soft, natural, and extremely accurate.

7. Return to the standard composite view. Press Ctrl+tilde (~) in a color image. In a grayscale image, press Ctrl+1.

8. Convert the mask to a selection outline. Ctrl-click the mask name in the Channels palette. Photoshop selects the most essential edges in the image without selecting the grain.

9. Choose Filter^ Sharpen^Unsharp Mask. In the last example in Figure 10-15, I applied the highest permitted Amount value, 500 percent, and a Radius of 2.0.

10. Whatever values you use, make sure the Threshold is set to 0. And always leave it at 0 from this day forward.

In case Figures 10-14 and 10-15 are a little too subtle, I include enlarged views of the great general's eyes in Figure 10-16. The top eyes show the result of using the Threshold value, the bottom eyes were created using the edge mask. Which ones appear sharper and less grainy to you?

The High Pass filter falls more or less in the same camp as the sharpening filters but is not located under the Filter ^ Sharpen submenu. This frequently overlooked gem enables you to isolate high-contrast image areas from their low-contrast counterparts.

When you choose Filter ^ Other ^ High Pass, Photoshop offers a single option: the familiar Radius value, which can vary from 0.1 to 250.0. As demonstrated in Figure 10-17, high Radius values distinguish areas of high and low contrast only slightly. Low values change all high-contrast areas to dark gray and low-contrast areas to a slightly lighter gray. A value of 0.1 (not shown) changes all pixels in an image to a single gray value and is therefore useless.

Figure 10-16: Enlarged views of the last examples from Figures 10-14 (top) and 10-15 (bottom). A good edge mask beats the Threshold value every time.
Photoshop Secrets

Photoshop Secrets

Are You Frustrated Because Your Graphics Are Not Looking Professional? Have You Been Slaving Over Your Projects, But Find Yourself Not Getting What You Want From Your Generic Graphic Software? Well, youre about to learn some of the secrets and tips to enhance your images, photos and other projects that you are trying to create and make look professional.

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