A scanned image may be saved as a Mac document in a variety of formats. The TIFF format stores a great deal of information about the shades of grey, or greyscale, in the picture-up to 256 shades. RSG can work with 128 shades.
Whatever the display capabilities of your monitor, you can print a picture with up to 128 shades of grey-depending on your printer.

NOTE: Though PICT and EPSF formats can also store information about shades of grey, you cannot use RSG to modify this information and change a PICT or EPSF greyscale picture as described in this section.

With RSG, you can affect how a TIFF greyscale picture is displayed and printed. You can create special effects such as making a negative, posterizing, and solarizing when you assign different shades to the original greys in a picture.
The Image Control dialog box lets you fine-tune the display and reproduction of a TIFF greyscale picture. The box with the diagonal line is the greymap box. This box shows how the original greys in a TIFF picture relate to, or map to, the greys displayed on screen or printed.
The horizontal axis represents the 128 shades that may be in the picture document. The vertical axis represents the same 128 shades that may be shown on the screen or printed. As the axes go up or to the right, the grays go from darkest to lightest. The diagonal line has 128 dots, each representing how a shade in the picture relates to the same shade on the screen or on printed copy. If you change this one-to-one correspondence, any shade of grey in the picture document can appear on the screen (or in printed copy) as a lighter or darker shade. For example, if you shift up shade 10 in the greymap box, then the shade 10 in the original picture document will appear lighter wherever it appears on screen or is printed.

NOTE: Don't assume that a picture you see on your screen is the way it will print. You may need to experiment with the following procedures to print a picture at its highest possible quality.