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

Nicholas, et al,

The Darkroom Automation meter read 6.01 for the ambient light in the room 
(sfelight) and 4.60 for a portion of the projected negative early in the day, 
with a 0.01 or 0.02 fluctuation. At other times in the day I've seen the 
ambient light dip to 5.95 and the reading down to 4.51. During long exposure - 
up to a minute or so, the reading goes up or down by 0.01 or more, but for the 
most part stays the same. But it does give different reading throughout the day.

Will a voltage regulator like the one in the link solve that problem?
http://www.pcconnection.com/IPA/Shop/Product/Detail.htm?sku=459725&oext=1038A&ci_src=14110944&ci_sku=459725

Elias

 -------------- Original message ----------------------
From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
> "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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