[pure-silver] Re: Same Exposure Different Prints?

"Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
Indescant lamps do not vary in output with temperature as do gasseous discharge lamps. However, they _are_ sensitive to voltage. I suggest getting a cheap voltmeter and monitoring the line. 

Or, rather than a _cheap_ voltmeter, one can use an
_economical_ enlarging meter....

The enlarging meter is a very good indicator of varying
household power. The meter shows light output to 0.01 stop, and will show variations in light output that are well below any that will effect the paper. If the meter reading is steady 
the light output is steady.
If the light output is varying then the best solution is a CVS Sola transformer. They show up on ebay quite often. They 
are hot and noisy.  I have a set of bypass switches on mine and
only switch it into the circuit when it is needed.
Loose connections in the sockets and wiring for halogen lamps are a common source of varying light output.
Cold-light heads are cans of worms all their own. Using a Sola, keeping the lamp on all the time and timing the exposure with a shutter is possibly the only -guaranteed- method of stable light output. A closed-loop stabilizer can be used in lieu of Sola 
and may be a better choice if the darkroom temperature varies a
lot.

Speaking of which - how is jjs getting on with the Saltzman?
I think Nicholas Lindan's timer compensates for varying brightness 

Nope, the timer isn't compensating. And really, it shouldn't
be.  I designed graphic arts exposure integrators for 20 years;
from this experience I have become convinced that exposure compensation isn't the way to go - regulated light output is. 
For very high precision systems a combination of integration and
regulation is needed - such a level of performance is well beyond the needs of photographic imaging. 


==
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121

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