Adobe ACROBAT 3D Manual page 721

Grayscale working space options
You can specify a Grayscale working space profile that is based on the characteristics of a
particular dot gain. Dot gain occurs when a printer's halftone dots change as the ink
spreads and is absorbed by paper. Dot gain is the amount by which the expected dot
increases or decreases. For example, a 50% halftone screen may produce an actual density
of 60% on the printed page, exhibiting a dot gain of 10%. The Dot Gain 10% option
represents the color space that reflects the grayscale characteristics of this particular dot
gain.
Original image, proof (no dot gain), and printed image (with dot gain)
You can also specify a Grayscale working space profile that is based on the characteristics
of a particular gamma. A monitor's gamma setting determines the brightness of midtone
values displayed by the monitor. Gray Gamma 1.8 matches the default grayscale display
of Mac OS computers and is also the default grayscale space for Photoshop 4.0 and
earlier. Gray Gamma 2.2 matches the default grayscale display of Windows computers.