Apple Macintosh PhotoFlash - Manual (Page 84)

For help deciding which setting to use for a specific image, see the next
section, “Deciding How Many Colors to Use.”
3 If you want the image to be dithered, make sure the Dithered checkbox is selected.
You can select the Dithered checkbox only if you are reducing the number of
colors used by the image. A dithered image is displayed using a technique that
changes the colors of some adjacent pixels to create the illusion of more
colors. For example, dithering can give the effect of shades of gray in a black-
and-white image or of additional colors in a color image.
You may want to experiment with the Dithered option and see how it affects
the view labeled After in the dialog box. In many cases (but not all), dithering
improves an image’s appearance.
4 Click Change.
The image information changes as you specified. If you don’t like the change,
choose Undo Depth Change from the Edit menu and try again.
Deciding how many colors to use
If you’re not sure how many colors (or shades of gray) to use for a particular
image, keep these general guidelines in mind:
m Reducing the number of colors used by an image decreases its size when
saved to disk, but it may also reduce the image’s quality when displayed on
screen or printed.
m Reducing the number of colors used by an image may mean that it prints
more quickly, but (depending on the printer you’re using) it doesn’t
necessarily reduce the print quality.
Some file formats limit the number of colors (or shades of gray) that images
saved in those formats can use. The section “Number of Colors or Grays
Supported by Standard File Formats” in Chapter 6 lists the number of colors
or grays you can specify for the standard file formats supported by
PhotoFlash.
74 Chapter 4