Re: Imaging

Albert Yan (pointnshoot@earthlink.net)
Thu, 19 Sep 1996 21:42:08 -0700

Beakman wrote:
<...pretty good description of halftoning!...>=20

> Dan Burkholder uses a slightly different method. He doesn't use a
> linescreen. Instead, he uses a "bitmap". The bitmap is prety much the
> same as a linescreen, except that rather than using a regular pattern o=
f
> dots, the "dots" -- which in this case look like little squiggly worms =

--
> are random.  Think about a mezzotint -- sort of like that, but on a muc=
h
> finer scale.
>=20

What you're referring to here is just another way of producing a=20 simulation of a contone image using a bilevel (black and white only,=20 no gray) process. The squiggly "worm-like" pattern is produced by an=20 algorithm called error diffusion. Yet another method that produces no=20 really discenible pattern, thus allowing finer granularity without the=20 problem of moir=E9 is stochastic screening, in which the bilevel dots=20 are distributed randomly. Integrated over some given area, however,=20 all these methods produce an equivalent of the average grey of the=20 origianl image in that same area. (Sounds not too clear....let me know=20 if it isn't and I'll try to clarify.)

> > Also, when you say cost is $20 to $25, is that > for 8x10? > What would 16 by 20 cost? Or does it do 16x20? >

Imagesetters come in different sizes and produce negs of different=20 widths. What your local shop can produce for you will depend entirely=20 on their equipment. Ther IS an upper limit, but I don't know what that=20 would be now. Last I looked it was about 16" wide. =20 <...>

Albert