Images and Page Design > Previewing and controlling dithering in Photoshop images > Previewing and controlling application dither
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Previewing and controlling application dither


You can preview application dither in GIF and PNG-8 images. The Dither Algorithm pop-up menu in the Save For Web dialog box lets you choose a dithering method for the image. The Dither percentage slider lets you control the range of colors simulated by dithering. 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, use the lowest percentage of application dither that provides the color detail you require.

Images with primarily solid colors may work well with Dither set to none. Images with continuous-tone color (especially color gradients) may require dithering to prevent color banding.

To choose a dithering method:

Select an option from the Dithering algorithm pop-up menu in the Save For Web dialog box:

  • No Dither applies no application dither to the image.
  • Diffusion applies a random pattern that is usually less noticeable than Pattern dither. The dither effects are diffused across adjacent pixels.
  • Pattern applies a halftone-like square pattern to simulate any colors not in the color table.
  • Noise applies a random pattern similar to the Diffusion dither method, but without diffusing the pattern across adjacent pixels. No seams appear with the Noise dither method.

    • To specify the amount of application dither applied:

    1 Choose a dithering method from the Dither algorithm menu. To specify no dithering for the image, select No Dither from the menu.

    2 If you selected any option other than No Dither in step 1, drag the Dither slider or enter a value to select a dithering percentage.

    Dither algorithm menu and dither pop-up slider

    Images and Page Design > Previewing and controlling dithering in Photoshop images > Previewing and controlling application dither