Smieglitz@aol.com
Date: 04/25/00-01:23:27 PM Z
In a message dated Tue, 25 Apr 2000 10:24:03 AM Eastern Daylight Time, "Christina Z. Anderson" <tracez@mcn.net> writes:
> ... So you are saying that fluorescent (sp)
> bulbs are duller and lower in contrast than two other artificial light
> sources? ...... (snip) In
> other words, wouldn't you have to test the same neg 4 times to really get a
> good judge of the issue, for perhaps it's the neg that is the problem (or
> the gum mixture, etc)? Is there visual proof?.....(snip)
> Chris
>
Here's a visual:
http://members.aol.com/kallitype/UV_Q.jpg
This is the first test of a quartz halogen FEL lamp vs. UV flurescents that I ran a few months ago. The gum emulsion appears fogged, not overexposed, or longer scale, etc. It is just plain fogged. This is only a preliminary test, but it sure surprised me. Obviously much more testing is needed but the results here would indicate that the UV tubes are not an ideal source for gum printing. Halogen lamps appear to print cleaner, with better separation and contrast with respect to the gum emulsion. I'll be testing more now that the current school semester is ending.
Before someone asks about controlling an infinity of variables in the test, let me say it is impossible to hold everything constant in a test of this nature. So the uncontrolled variable I chose was the time between exposures using the same negative. It was either that or introduce something else (e.g., paper coated at a different time, slightly different emulsion mixed at different times or the same emulsion sitting around and thus aged before the second exposure, different test negatives, etc.) I tried to match the maximum print density on the exposures and adjusted the distance/time of the FEL exposure to match the UV printer bank. I think the fogging is due to some elusive quality of the light source rather than the 7 minute lag between exposures. It might be due to some temperature effect caused by the sources heating the contact frame to different degrees, but I didn't notice any large difference (and also didn't measure for it either...next time).
Joe
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