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Mark,
thanks for pointing out other possible cause for
the unevenness.
I perfectly understand that one can consider a
short exposure time itself as a cause for unevenness but let's say we have a
large area of light uniform tone on our original, I'm sure you would want
it light and uniform on the print. Your negative would need to have a relatively
high uniform density in this area, right? As you probably know, within certain
limits, you can control exposure by varying either time or density. I could
have suggested to use a negative with a uniform and relatively high density for
this test, instead I choose to vary the time by about 3 stops to produce
the same effect, I think 3 stops is well within the range of
carbon.
Regards,
Yves
----- Original Message -----
Sent: Thursday, July 24, 2008 12:07
PM
Subject: Re: Light source
Yves,
Not unusual to get uneven tone when making short exposures with some
materials. It may be the light showing uneven coverage, but more likely
variance of speed of the emulsion itself. For example, with PT/PD, it
could easily be variances in moisture in the emulsion. For
carbon—perhaps moisture, perhaps uneven sensitization.
Best Wishes,
Mark Nelson
On Jul 24, 2008, at 10:12:39 AM, "Yves Gauvreau"
<gauvreau-yves@cgocable.ca> wrote:
Hi,
this
may interest some of you.
While testing for exposure time with a
friend, we realise that something was
let say bizarre and we decided to
test our light source. We exposed for 1/10
our standard exposure time to
obtain a mid to light gray. We made the test
print the same size as our
usual prints using no transparent materal.
As soon as we could see
the result, (carbon print) we where stunned, there
where major
differences in tone all over the print and all sort of
undesirable
artefacts.
We where using a point source and decided to try an UV
tube bed instead and
of course we will make another test just in
case.
The lesson learn from our experience may be useful to others
and I thought
we should share it with you.
Regards,
Yves and
Philippe
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