Re: Dots of gum?

From: Ender100@aol.com
Subject: Re: Dots of gum?
Date: Sat, 12 Feb 2005 17:09:07 -0500 (EST)

> Do you think it might also be that with a screened negative, you are
> printing "black and white dots" rather than continuous tone? Thus
> each dot receives the same amount of full exposure to harden it.
> Increased "Tone" is achieved when the dots are placed closer
> together in the screened negative.

He said he prints through a halftone screen, not halftoned negative.
So his exposure is still continuous tone with fixed size grating.

In real, old fashioned way to make halftone negative is to use
halftone screen somewhat off the negative, combined with right lens
and aperture, so that each "dot" on film has highest exposure at the
center and the exposure falls off as the radius increases. The film
often receives nonimage flashing on top of the imagewise
exposure. Then the film thus exposed is processed in classic lith
developer consisting of hydroquinone as the sole developing agent with
little sulfite. This type of processing gives very high contrast and
reasonably hard dot quality. But more recent lith films and developers
incorporate contrast enhancing agent (hydrazine compounds) and these
can be processed in rapid access type system, while offering improved,
rock solid, dot quality. Of course all these are obsolete with digital.

There were also some lith films preexposed with grid patterns so that
halftoned negative could be made with imagewise exposure only. Oh what
else... there were lots of stuff in this area but no more...

--
Ryuji Suzuki
"Well, believing is all right, just don't let the wrong people know
what it's all about." (Bob Dylan, Need a Woman, 1982)