Diffuse UVA LED Lighting

[dabateman]

Options for UV-A specific lighting to do UV induced fluorescence have been using either a Convoy S2+ flashlight to light paint the subject or using an expensive modified flash set up.

There are disadvantages to both setups.

 

The Convoy S2+ is cheap and can also be cheaply modified to UV-only using a small filter. However its spot is quite intense and narrow. While the intensity is good for fluorescence emission, it's also too intense and overwhelms a flower to wilt. I have specifically targeted flowers to collapse using the Convoy's intense beam. This may be due to too much excitation leading to local heating and wilting of the flower petals.

 

A modified flash is expensive, (unless you get a good cheap Canon 199A), but filters to make them UV-only are expensive. The advantage of the flash is very short duration, allowing for hand holding the camera and flash unit. However this short duration can also be a limiter on the excitation of the subject. There is a time needed to fully excite the chromophores in a subject to get the best output of fluorescent emission. In simpler terms, if you provide UV light for more time, you are providing more energy to allow the subject to provide (emit) more beautiful visible and IR light.

 

An alternative low cost option I have been playing with is simply modifying a LED 365nm Light bulb. The Lixada 7W 365nm LED light bulbs can be purchased quite cheaply at times. I got mine for under $20, but I now see they are $26 on Amazon today. They have a A19 bulb type and E26/E27 socket. So they fit in a common European or North American light socket (like a desk lamp). The A19 refers to the bulb shape, and for all LEDs I have played with a plastic dome is used.

 

You can cut the plastic dome off an A19 bulb with a Dremel tool, or if you're really careful, use an Exacto knife. I cut about 1 to 2 cm from the base. Then a 55mm to 52 mm step down ring will fit over the cut plastic. Alternatively if you have extra empty 52mm rings, you can just fit them inside the cut bulb. Here is an image of my Lixada bulb cut with 2 empty 52mm rings:

 

I used black electrical tape which I know blocks all light, to block all light from the base of the bulb. This can be used to hold the 55-52mm step down ring in place and block all the light. For this 365nm bulb, I placed the 52mm rings inside while the plastic was still a little hot from cutting. So the rings are stuck in place and don't need tape to hold them in. Here is an image with the same bulb and a 1.8mm ZWB1 52mm filter I have:

 

This allows for a diffuse UV-A only lighting, which can be controlled by lamps to be close or far from the subject. The disadvantage of using a bulb, is that it is not portable. So this only works for my UV dedicated area in the basement, and can not be easily used outside in a field. However, they may be older flashlights that take E26/E27 bulbs, I am not sure.

[Cadmium]

Ever try something like this? Have to find one with the right wavelength, voltage, size (for filter glass), etc....

https://www.ebay.com/sch/i.html?_from=R40&_nkw=365nm+UV+flood+light&_sacat=0&LH_TitleDesc=0&LH_TitleDesc=0&_sop=15

[Cadmium]

I have never tried these... I suppose someone has around here.

Working input voltage on this one is: 85-265V AC.

Depending on glass size, would be fairly easy to replace front glass with filter glass, or add on front.

https://www.ebay.com...&frcectupt=true

[dabateman]

I haven't used one like that. Adding larger filter may be expensive though. As with my bulbs, I can use my 52mm filters. These are cheap for 385nm output. I tend to like the golden 365nm, though.

However, its a good idea to look into if I get more space in the basement, and you could wire multiple with switches.

[Cadmium]

Aren't the 10W floods about the same price? Lixada is 7W?

These floods are available in higher wattage, although the filter glass gets a bit large on some. Need to keep it down to 165mm x 165mm.

Hard to say, have neither to compare. Need to test/compare heat output for the glass/filter.

(I have SEEN UV filters that people completely destroyed attaching to some lights)

Any of these would need to be tested and compared for actual nm peak and light intensity... they all make claims...

Just like there are tons of UV torches on eBay, but none come close to working as well as as the ones with Nichia LED's.

[Andrea B.]

David, this is a very nice mod for the indoor studio. Thank you for the write-up!