From: William Laven (wmlaven@platinotype.com)
Date: 02/11/00-04:23:06 PM Z
>
>As I originally stated, the output goes through it's most dramatic
>changes at the very beginning, so I would recommend "seasoning" the
>lamps for at least 100 hours before trying to establish any type of base
>exposure times. In the chart from Philips, the curve is still quite
>vertical out to about 300 hours, and then curves to a slight downward
>straight line by 1000. When the lamps are young, you are going to have
>problems getting a reliable base exposure time.
This is exactly why the Metrolux timer or a light integrator is so good for
exposure units. Why burn lamps for 100 hours when you could be printing
then and still achieving predictable consistent exposures with a light
integrator/Metrolux?
Also, while the Philips graph indicates such a precipitous drop, I've not
seen that with my printers (several of my own and several which I use in
workshops). That is, my exposure times didn't have dramatic increases in
response to the suggested decrease in lamp output.
I wonder whether others' experience is similar or different.
Curiously, a few days ago I was printing and the exposure times were
consistently faster than they were a year or so ago when I last did a
calibration on the Metrolux,suggesting that the lamps' output had
increased! Go figure.
********************************************************************
WILLIAM LAVEN PHOTOGRAPHY
Tutorials in Platinum/Palladium printing and Zone System.
1931 23rd Street, San Francisco, CA, 94107
415-647-9432 (voice) 415-647-9438 (fax)
wmlaven@platinotype.com
http://www.platinotype.com
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