Proper Exposure shouldn't be guesswork

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From: Jack_Rosen_CFRM (Jack_Rosen_CFRM@hotmail.com)
Date: 06/19/01-06:02:47 PM Z


Hopefully this is helpful, I've had a lot of experience on this subject.

My first question is why no one is determining
these exposures by using step tablets and filters to
determine the range / sensitivity of the medium of choice. ?

I've been using a 14 lamp, 7 over/ 7 under glass plate exposure unit.
The cover slip is an acetate base, strung in a lexan frame.
There are some differences between the upper/lower exposure due
to the attenuation of the 365nm by glass/acetate.

I use 2 timers that are programmable interval to attain equal exposure
top/bottom.

The lamps are 365nm UV rich 18" long and 15 watts each.
I jog the contact frame equal to half the distance between the lamps
to even out the exposure over a 2 minute period.

I never found the need for reflectors internally on the fixtures.

That's the 'old system' here, been in service 15 years.
I replace the starters every year and there are enough variations
that I buy 30 starters and take a few days to let the tubes cool down
between firings to attain equal start intervals.

This is what replaced the 'point source' due to it's output limitations
and edge fringing / edge under exposure (great for softening edges).

It's never been guesswork, just simple tools.

jr

----- Original Message -----
From: "Richard Sullivan FRPS" <richsul@earthlink.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, June 19, 2001 5:30 PM
Subject: More on light source differences


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