Light (and UV) output of flourescent tubes.

In summary, the conversation is about finding a source of UVA light for photographic printing. The participants suggest using fluorescent lights with mercury or UV LED lights. They also mention UV blacklight LEDs and germicidal lamps, but warn about the potential hazards associated with them. The use of blacklight tubes is suggested for exposing photoresist or Azo materials, and the importance of proper exposure and avoiding hot-spotting is discussed. The conversation ends with a recommendation to test different exposure times to find the best results.
  • #1
matthyaouw
Gold Member
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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

Thanks in advance,

Matt
 
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  • #2
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
I was going to suggest the UV LED also, but I didn't know how much intensity and the exact wavelength you might need. However, I picked up one of those UV flashlights off ebay http://www.ebay.com/itm/UltraFire-WF-501B-LED-Flashlight-375NM-UV-Ultra-Violet-Blacklight-Torch-18650-/161161947959?pt=US_Flashlights&hash=item2586002b37 for around $12. Might be worth a try to see how close it gets you. Most of those lights use a Li-ion 18650 cell by the way.
 
  • #5
Also, we used to use UV source to erase the eproms. I have a home made unit I built with a 4" UV tube (dangerous type - clear glass) you did not want to look at it for very long. (My homemade unit worked better than the $100 unit we had because I could load more eproms in it. (Used to change the program and test faster than the erase time) I'm sure many of those can be found, but again I don't know if that meets your intensity, wavelength or area requirement.
 
  • #6
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
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.
 

FAQ: Light (and UV) output of flourescent tubes.

1. What is the difference between visible light and UV light in fluorescent tubes?

Visible light is the light that is visible to the human eye and is responsible for the illumination of our surroundings. UV light, on the other hand, is invisible to the human eye and has shorter wavelengths than visible light.

2. How does the light output of fluorescent tubes compare to incandescent bulbs?

Fluorescent tubes have a higher light output than incandescent bulbs, meaning they produce more light for the same amount of energy. This is because fluorescent tubes convert more energy into visible light rather than heat, making them more energy-efficient.

3. Do fluorescent tubes emit harmful UV radiation?

Yes, fluorescent tubes do emit some UV radiation, but the amount is significantly lower than that of natural sunlight. However, it is still recommended to limit exposure to fluorescent tube light, especially for people with light sensitivity or skin conditions.

4. How does the light output of fluorescent tubes change over time?

The light output of fluorescent tubes decreases over time as the phosphor coating on the inside of the tube gradually degrades. This is why it is important to regularly replace fluorescent tubes to maintain optimal light output.

5. Can the light output of fluorescent tubes be adjusted?

Yes, the light output of fluorescent tubes can be adjusted by changing the ballast or using a dimmer switch. However, this may affect the lifespan and efficiency of the tube. It is important to consult the manufacturer's guidelines before attempting to adjust the light output of fluorescent tubes.

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