UV light output over life of source

Pete Bergstrom (bergstro@src.honeywell.com)
Sun, 16 Jul 95 15:02:21 CDT

In considering how to measure actinic light levels for exposure
consistency, I've become curious about the consistency of UV output
relative to the other wavelengths of light sources. In particular, I'm
interested in hearing how people determine they need to replace their UV
bulbs.

The reason I ask this is that I've recently acquired a Metrolux II enlarger
timer to which I may attach a light sensor (the normal use is to monitor
the output of a cold light head for making enlargements) but which might
also be used as an actinometer of sorts. If whatever wavelengths to which
this sensor is sensitive accurately predict the UV level, this might be
very useful.

Is it the case that people not using NuArcs or similar commercial setups
just don't bother measuring the light and instead proceed on a trial-and-
error basis?

If so, how do you deal with the need to make prints over intervals of
several months or years? Redo the testing for each session?

Thanks,
Pete