Digital BW, The Print

Richard writes:

> My question - Aren't all inkjet printers required
> to use a dither by definition?

Not really.  Dithering is a process in which two or more pixels are assigned
two or more different colors, with the expectation that the human eye will
see the two pixels blend into some intermediate color that cannot be
directly represented in a single pixel.  For example, if you have only three
possible colors for your pixels (in the world's cheapest inkjet printer,
useful for hypotheses like this one), the only way to represent more than
three colors is to dither and hope that the image will be viewed from far
enough away that the dithered pixels will blend in the eye of the viewer,
producing a perception of some intermediate color.

So dithering is not required for an inkjet printer, but many printer drivers
will use it in some modes to produce intermediate tones that cannot be
represented exactly with a single pixel color.

Dithering is common in 256-color modes on computer monitors.  It's not
necessary in 24-bit color modes, as a general rule (although I think
Photoshop still dithers generated gradients in some cases).