Don Stauffer said:
DPI makes a difference. Few decent priced laser printers have a high
dpi. The higher the dpi of the printer, the greater the number of dots
in each pseudo-pixel, and hence the higher the grey scale it can use.
Both laser printers and inkjets use the same sort of diffusion dither
to create 'mock' halftone cells. The more dots in each cell (a cell is
the same as a pixel) the more grey tones available. Thus high dpi
inkjets will have more tones than most lasers.
Even some of the dye subs dither. While many dye subs can alter the
amount of ink per dot, on some dye sub printers the amount of variation
is still not good enough for a large number of shades, so both
variation of dot size AND dithering are used.
But, there is also the matter of bit depth, if you buy a new half decent
laser it will be able to vary the intensity of each dot, usually either
a 4 bit depth or 8 bit. As far as I can tell on non-production machines
this is done by varying the dot size. I _believe_ but haven't been able
to confirm it, that production machines vary the intensity by some
method involving the amount of developing that takes place as they tend
to be two stage prints using developer and toner.
For instance my new machine here a Minolta Bizhub says 256 shades per
pixel and 600 dpi - consequently it prints a very nice monochrome (and a
very nice colour). But the old machine a Canon CLC also said 256 shades
per pixel and only 400 dpi and it did produce a nicer copy - which it
should do as its equivalent model today is about 4 times the price of
the bizhub.
If you get a decent resolution an old black laser can produce a good
copy. I remember printing some pictures on an HP IIIP, the dot pattern
was noticeable if I tried to enlarge during printing, but as long as I
printed at the printer's 300dpi resolution it was fine, - so an
1800x1200 picture would get printed 6" x 4"