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

Re: intensity of bulbs

  • To: alt-photo-process-l@usask.ca
  • Subject: Re: intensity of bulbs
  • From: etienne garbaux <photographeur@nerdshack.com>
  • Date: Mon, 23 Feb 2009 23:37:18 -0500
  • Comments: "alt-photo-process mailing list"
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Barry wrote:

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