# Light (and UV) output of flourescent tubes.

1. Feb 27, 2014

### matthyaouw

Hello all,
Long time no see.

I am hoping to find someone with knowledge of light output (in particular UVA output) of fluorescent tube lights. I have 2 questions:

-Should I expect the light output of a 20 watt CFL bulb and a 20 watt 2 foot long fluorescent tube to be the same, or different (allowing for variation between manufacturers)?

-Will BL lights (such as for bug-zappers) emit more UVA than BLB lights (such as for security checking passports, raves etc)?

Basically I need a source of UVA light for photographic printing and am trying to find the best way to light an area the size of A3 paper as brightly as possible for relatively little cash. I have a couple of CFL BLB lamps but am considering replacing them as they are a bit on the weak side for me. Mercury vapour is out of the question due to cost, so I think I'm pretty much confined to fluorescent. Presence or absence of visible light is not an issue. The collective knowledge of google seems quiet about the subject and I am unsure where else to ask

Matt

2. Feb 28, 2014

### Baluncore

Fluorescent lights have some mercury to provide the UV spectrum that then drives the phosphor to fluoresce at longer wavelengths.

Have you considered the new UV Blacklight LEDs? 3W, UV at 395nm.

3. Feb 28, 2014

6. Mar 2, 2014

### matthyaouw

Thanks for the input. I have gone with a couple of blacklight fluorescent tubes for the moment mainly because I don't seem to be able to get much else near home. LEDs could work but it seems many are more violet than ultraviolet and I don't want to spend an age wiring something up that might not work. I'm avoiding germicidal lamps because I think I need UVA rather than UVC.

7. Mar 9, 2014

### RBTO

You mention "photographic printing". Are you exposing photoresist or Azo materials? If that's the case, blacklight tubes should work fine. It's best to stay away from the shortwave UV entirely due to hazards associated with shortwave UV, and most materials respond to longwave UV pretty well (some caution is warranted there also). In any case, you can probably compensate by using longer exposures since exposure of most of those materials doesn't call for UV at a specific wavelength, and the sensitivities have a fairly wide span of wavelengths. You may have to adjust the spacing and distance of your tubes to prevent hot-spotting (more exposure in one area than another). You can test for the proper exposure by making a series of test exposures using varying lengths of time to see what works best.