Photoshop 6 for Windows Bible- P7

Photoshop 6 for Windows Bible- P7:If you are reading this foreword, it probably means that you’ve purchased a copyof Adobe Photoshop 6.0, and for that I and the rest of the Photoshop team atAdobe thank you.If you own a previous edition of the Photoshop Bible, you probably know what toexpect. If not, then get ready for an interesting trip.
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Photoshop 6 for Windows Bible- P7 Chapter 4 ✦ Defining Colors 147When you choose Image ➪ Mode ➪ Bitmap, Photoshop displays the Bitmap dialogbox, shown in Figure 4-5. Here you specify the resolution of the black-and-whiteimage and select a conversion process. The options work as follows: ✦ Output: Specify the resolution of the black-and-white file. If you want control over every single pixel available to your printer, raise this value to match your printer’s resolution. As a rule of thumb, try setting the Output value some- where between 200 to 250 percent of the Input value. Figure 4-5: The Bitmap dialog box converts images from grayscale to black and white. ✦ 50% Threshold: Select this option from the Use pop-up menu to change every pixel that is darker than 50 percent gray to black and every pixel that is 50 percent gray or lighter to white. Unless you are working toward some special effect — for example, overlaying a black-and-white version of an image over the original grayscale image — this option most likely isn’t for you. (And if you’re working toward a special effect, Image ➪ Adjust ➪ Threshold is the better alternative.) ✦ Pattern Dither: To dither pixels is to mix them up to emulate different colors. In this case, Photoshop mixes up black and white pixels to produce shades of gray. The Pattern Dither option dithers an image using a geometric pattern. Unfortunately, the results are pretty ugly, as demonstrated in the top example in Figure 4-6. And the space between dots has a tendency to fill in, especially when you output to a laser printer.148 Part II ✦ Painting and Retouching ✦ Diffusion Dither: Select this option from the Use pop-up menu to create a mezzotint-like effect, as demonstrated in the second example in Figure 4-6. Again, because this option converts an image into thousands of stray pixels, you can expect your image to darken dramatically when output to a low- resolution laser printer and when reproduced. So be sure to lighten the image with something like the Levels command (as described in Chapter 17) before selecting this option. Figure 4-6: The results of selecting the Pattern Dither option (top) and the much more acceptable Diffusion Dither option (bottom). ✦ Halftone Screen: When you select this option from the Use pop-up menu and press Enter, Photoshop displays the dialog box shown in Figure 4-7. These options enable you to apply a dot pattern to the image, as demonstrated in Figure 4-8. Enter the number of dots per inch in the Frequency option box and the angle of the dots in the Angle option box. Then select a dot shape from the Shape pop-up menu. Figure 4-8 shows examples of four shapes, each with a frequency of 24 lines per inch. Chapter 4 ✦ Defining Colors 149Figure 4-7: This dialog box appears when you select theHalftone Screen option in the Bitmap dialog box. Round Diamond Line CrossFigure 4-8: Four random examples of halftone cell shapes. In all cases, theFrequency value was set to 24.150 Part II ✦ Painting and Retouching Cross- I cover screen patterns and frequency settings in more depth in the “Changing Reference the halftone screen” section of Chapter 18. ✦ Custom Pattern: If you’ve defined a repeating pattern using Edit ➪ Define Pattern, you can use it as a custom dither pattern. Figure 4-9 shows two cus- tom examples. I created the first pattern using the Twirl Pattern file, which is stored in the Displacement Maps folder in the Plug-Ins folder. I created the second pattern manually using the Add Noise, Emboss, and Ripple filters (as discussed in the “Creating texture effects” section of Chapter A on the CD-ROM for this book). Figure 4-9: Two examples of employing repeating patterns (created with Edit ➪ Define Pattern) as custom halftoning patterns. Cross- For a complete guide to creating and defining patterns in Photoshop, see the Reference “Applying Repeating Patterns” section of Chapter 7.Photoshop Chapter 4 ✦ Defining Colors 151 6 To use a custom pattern, open the Custom Pattern palette in the Bitmap dia- ...