Adobe 29180155 User Guide - Page 274

ADOBE PHOTOSHOP ELEMENTS 4.0 269 User Guide Dithering simulates continuous tones Use colors in the Web palette to ensure that colors won't dither when displayed on Windows or Mac OS systems capable of displaying 256 colors. When creating an original image, you can use the Color Picker to choose web-safe colors. When optimizing images, keep in mind that two kinds of dithering can occur: Application dither Occurs in GIF and PNG-8 images when Photoshop Elements attempts to simulate colors that aren't in the current color table. You can control application dither by choosing a dithering pattern, or you can try to avoid application dither by adding more colors to the table. Browser dither Occurs when a web browser using an 8-bit color display (256-color mode) attempts to simulate colors that aren't in the 8-bit color palette. Browser dither can occur with GIF, PNG, or JPEG images. In Photoshop Elements, you can control the amount of browser dither by shifting selected colors in the image to web-safe colors. You can also specify web-safe colors when choosing a color in the Adobe Color Picker. You can preview application dither in GIF and PNG-8 images. Images with primarily solid colors may work well without dithering. Conversely, images with continuous-tone color (especially color gradients) may require dithering to prevent color banding. See also "Optimized file formats for the web" on page 259 "To use the Adobe Color Picker" on page 223 "To optimize as GIF or PNG-8 format" on page 263 To control dither in web images 1 In the Editor, open an image and choose File > Save For Web. 2 Choose your optimization settings. 3 Enter a value in the Dither text box or click the Dither menu arrow and drag the slider that appears. 4 The Dither percentage controls the amount of dithering that is applied to the image. A higher dithering percentage creates the appearance of more colors and more detail in an image, but can also increase the file size. For optimal compression and display quality, use the lowest percentage of application dither that provides the color detail you require.