In a message dated 97-10-31 20:46:57 EST, richsul@roadrunner.com writes:
> Placing the bulbs further away will not sacrifice very much printing speed
> until you get pretty far away. Almost no loss until the distance exceeds
the
> minimum width and then only minimal. The sqare of the distance law is only
> for *point sources* For that to be in effect you would have to be far
enough
> away from the light bank for it to appear for all practicle purposes as a
> point source, say 25 to 50 feet. I think it was Bob Schramm who worked out
> the math on this last winter for us when the topic came up. Likewise if the
> tubes are close together, you can lay the print frame directly on them with
> no visible banding. Weird I know but it works.
>
Dick- we tried a test tonight using a metro-lux and it didn't prove out as
above.
one lux with light source 6 inches from probe surface was six seconds while
one
lux with light source 2 feet from probe was 15 seconds. The light source was
16- 90 watt blubs with a total width of 25 inches and length of 3 feet.
Working on the large prints we've been doing latelyI've noticed that our
exposure times have increased greatly even though the "lux" eposures have
remained the same. ie a 45 lux exposure with the exposure unit 2-3 inches
from print is about 4 1/2 mins
when the unit is 2 feet above print it is more like 15 mins. It amazing how
when theory meet reality- reality usually wins out. Any thoughs on this?
David Kennedy