Digital BW, The Print

Herb writes:

> While your "world's cheapest inkjet printer" may
> have only three possible pixel colors, there are
> lots of color inkjets that have only four possible
> pixel colors (CMYK) and lots more that have
> only six colors (like many of our Epsons).

Nope.  You are confusing dots and pixels.  Machine dots can only have as
many colors as there are inks, on machines with opaque inks (such as
inkjets).  However, pixels are made up of multiple dots on such machines,
and so they can have quite a few colors, depending on how the individual
dots are mixed.

> My understanding is that inkjets do indeed dither
> to create colors, but that the pixels are so small
> that for all practical purposes we can consider
> them to be "continuous tone" printers (rather than the
> dithering class of "half-tone" printers).

Some do dither.  However, you can see individual dots and dithering on the
page with a loupe, so I wouldn't say that the pixels are small enough to be
call continuous tone.

If you want something closer to continuous tone, use dye sublimation.

> Dye sublimation printers can print a solid color
> other than CMYK and are truly continous tone,
> but I don't think inkjets are.

Yes.

> Inkjets could be, I suppose, if the inks they
> spray mixed to form a new color, but that's not
> what happens.

Yes.  But you need transparent inks and a way to control the amount of ink
deposited (not just the size of the dot) in order to accomplish that.
Dye-subs do it by varying the thickness of dye deposited on a spot and by
using dyes that are transparent.  This can't be done with inkjets for the
most part, particularly with pigmented inks, which tend to be highly opaque.