Digital BW, The Print

Martin writes:

> The inks are not opaque, even the pigment inks.

I know.  Neither are offset printing inks.  But for practical purposes, they
are generally treated as opaque.  They do not have the transparency of
dye-sub or chemical emulsions, and I do not see whatever transparency they
possess ever being used in actual printing.  If inkjet printers had reliably
transparent inks, they would print like dye-sub printers, and you'd be able
to get a true 2880 ppi on the print.

> So drops of ink can be placed on top of each
> other to create intermediate tones.

That doesn't appear to be happening on the inkjet prints I've examined.

> I believe that the inks used in offset printing
> are quite different from those used in inkjet
> printers.

They probably are, but a common characteristic between the two is opacity.

> Your logic is partially correct for something like an
> image setter or standard laser printer but the fact
> that the different inks can be overlaid to create
> different tones or hues, and the use of dither patterns
> suggests that you can simulate much more than the math
> implies.

Dithering dramatically reduces resolution, so I don't count that.  Close
examination of the prints from my 2000P (and indeed of any inkjet prints
that I've looked at thus far) reveals adjacent dots of ink, not overlaid
dots of ink.  If you look closely enough, the image always shows a slight
grain from this adjacent placement, like that of a stochastic halftone
screen in offset.

In contrast, dye-sub printers overlay transparent inks directly, and the
prints from my Alps MD-2300 (which unfortunately I no longer use, because
supplies are scarce and the printer is far too finicky) show razor
sharpness.  Under the loupe, each pixel is clearly distinct, with its own
color and intensity, and there is no dithering or grain.  I wish Epson made
dye-sub printers--with this quality but with the reliability and
user-friendliness of other Epson printers.  It's just too much trouble to
get stuff printed on the Alps, but it sure did a beautiful job--the results
could not be distinguished from a chemical print (and would tolerate
scrubbing under a stream of water without any visible damage).

> If what you say was correct, I doubt that we would
> be very pleased with out digital prints, color or B&W.

I'm not.  They look nice from a distance, but they always lack sharpness
upon very close examination, just like halftone images in a magazine.

> I believe it would be more correct to say that
> a modern inkjet printer interprets pixel input
> rather than to say it prints pixels.

That's true, but it is still constrained by the opacity of inks.