From: Judy Seigel (jseigel@panix.com)
Date: 09/24/03-02:50:36 PM Z
On Wed, 24 Sep 2003, Sandy King wrote:
> The most likely reason for the low contrast is the negative. Most
> people don't realize that the classic VDB mix requires a negative
> with a *very* high density range to print with good contrast. By that
> I mean a DR of log 2.25 and even higher, which is much higher than
> you can get with OHP material with most printers. You can test the
> premise by just printing a plain sheet of the OHOP material, using
> test strips of different times to make sure you are getting enough
> exposure.
>
I believe it's futile to talk about "contrast" or "density" in the
abstract.... you need to run a test with a 21-step sensitivity guide and
then read the steps -- getting both the number of steps and the difference
between step zero and the surround ("D-Max").
However in my experience the most common cause of low density in VDB is
blowout from heat dry -- even a small amount of heat applied to the wet
unexposed emulsion can kill... Of course double coating should increase
D-Max (except on those papers where it wipes emulsion off & reduces it),
but in any event air dry at room temp & expose promptly.
Judy
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