Re: Dots of gum?

On Sat, 12 Feb 2005, Katharine Thayer wrote:

> But I realized that something isn't making sense to me about this. The
> argument has always run this way: somehow these discrete dots of gum
> that are laid down by halftone or stochastic dot negatives stick to the
> substrate better than gum that's not laid down this way. But here's the
> problem I have with this argument: since it's the negative that is made
> of discrete dots, what prints on the gum isn't the discrete dots. What
> prints is the space around the dots. So I don't get this argument; could
> someone make this work for me?

Here I'm partly guessing (or surmising), and partly extrapolating from
long-ago experience and talk with a Kodak honcho when I was testing Kodak
lith film and developers.

I don't think the issue is whether you're printing "dots" or their
surround. That is, it's not the *shape*; it's the construction. A contone
negative has unequal density (for the highlights or shadows depending on
whether positive or a negative) that gets fainter and fainter until some
of the marks are thin and light. That is, more "off" than "on," plus lots
of inbetween. The fainter marks are less exposed, less substantial, than
fully exposed, and their emulsion therefore more easily washed away.

In a halftone negative, there are no such inbetweens. Everything that's
supposed to be exposed is full bore; the edges, whether of the surround or
the dot, are clear cut -- either "on" or "off," thus the partial tones
don't handle differently (or not very differently) than full tones. In
some (all?) halftones the thinner tones get smaller dots (or, as I recall,
used to anyway), so that may affect printing, tho that's probably a
footnote, not this question.

That's my theory, anyway; if the premise is true, it's probably along
these lines.

Judy
Received on Sat Feb 12 16:12:39 2005