U of S | Mailing List Archive | alt-photo-process-l | RE: intensity of bulbs

RE: intensity of bulbs

Wooops! You're right of course - wattage is total output not per foot as I
was thinking.

Geoff Chaplin
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-----Original Message-----
From: etienne garbaux [mailto:photographeur@nerdshack.com] 
Sent: 24 February 2009 13:37
To: alt-photo-process-l@usask.ca
Subject: Re: intensity of bulbs

Barry wrote:

>Does a 24" bulb at 20 watts have the same intensity as a 48" bulb at 40

I would expect them to have the same intensity per unit surface area, 
so used in a light box they should give equal exposures (but you 
could do two prints at a time in the 48" unit because its total 
output is double).  This is confirmed to a first approximation by 
looking at otherwise-identical 24" and 48" tubes -- which you can 
often do in the lighting aisle of your local home improvement 
store.  Their surfaces appear to be the same brightness.  (No reason 
I can see why the same should not be true for actinic phosphors.)  If 
you Google for tube specs, you can probably find more precise information.

Best regards,