Optical density represents the range of color tonal values that the hardware can resolve. Obviously, the more discrete colors that the scanner can recognize, the more accurate the scanned image can be. Optical density is a logarithmic scale, so small increases are more significant than normal. This may be the single most important indicator of a scanner s quality. Of course, you probably won t be able to find this value in the specifications of most flatbed scanners.
Scanners offer a wide range of resolutions in advertisements.
A typical scanner even has two specified resolutions. They are the optical resolution and the maximum resolution. The optical resolution is the only important resolution and is the lower of the two. Actually, they are readings or measurements rather than dots. That would usually indicate 600 optical sensors along the width of the flatbed page.