Digital BW, The Print

----- Original Message -----
From: "royvharrington" <roy@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Sunday, August 04, 2002 8:45 AM
Subject: [Digital BW] Number of tones was Re: Do inkjets dither or not?


> The tradeoff of gray levels versus resolution is really the entire
> basis of what's going on in printing.  Previously in this discussion
> there was distinction of pixels versus dots, but I think this is
> an unnecessary and misleading distinction.  Everything we have as
> far as Epson printers these days are pixels. The very smallest point
> on a print can contain any of 4 or 6 different gray/black inks drops,
> plus with variable droplet size and overprint of multiple drops,
> there are many possible gray values.  So I would call this a
> pixel not a dot.  The printer 1440 and 2880 dpi specs relate
> to high resolution, a few grays pixels.  Through the dithering
> process we tradeoff those high resolution pixels to get pixels
> with lower resolution but more gray values.

Pixels as used in image files have their bit value bound to the pixel
itself.
Representations on monitor screens in dithering do not affect the image file
properties on that aspect.
What is shown on your screen in dithering could better be described as false
pixels.

The dot formed by one droplet of the inkjet has to be compared with the
image setter laser dot or line that builds the screen/raster dot on an
offset plate (filmless systems), the screendot is one form of a cell.
Growing from 1 laser dot to 256 laserdots it is the most defined form of a
grey value cell. Yet that rasterdot can have shapes like round, square,
oval, chain, line. The same laserdot can build cells in a stochastic
pattern, the frequency of the laserdots per area represents the gray value.
This is more a cloud than a shape. Those cells can even overlap one another
to some degree. Laserdots sometimes have similar variable sizes as inkjet
droplets have. This is used as well in the creation of cells.

The term 'weaving' for inkjet cell formation is a vague definition with a
reason. The process is complex with all kinds of methods to represent grey
values and one extra goal: get rid of the defined shapes of pixels or
screendots. Ink densities, droplet sizes, dithering, stochastic patterns,
inklayer variations are all combined to get that result. Cells overlap as
well. Printing is build up in 4 successive strokes that allows an increase
in complexity and avoids ink bleeding at the same time. It can be done in
inkjet printing, there's no way this can be done in a conventional printing
process. In all that complexity sharpness and contrast must not be lost. It
isn't.

The translation of pixels through printer resolution, dot size, dithering,
ink densities to cells that represent grey values can be done in so many
ways that the cell is a very amorf entity. In coIour printing this is even
more complex.
I wouldn't use the term pixel for a cell like that. A pixel is far more
defined except in its size.

Add to that the usual pixel data in additive RGB and the unavoidable
subtractive printing in CMY(K).

Ernst