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UltravioletPhotography

UV Spot


Harald

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I think the power specification is way too high just as normal illumination LED-lamps to be compared with an equivalent incandescent bulb.

That helps people find the right LED-bulb and judge from experience about the old style lamps.

 

It would be very nice if the power is the actual input power and the efficiency of the LEDs are good, but I would not bet on that.

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Funny I am waiting on 2 of those 36W 365nm flood lights.

Still haven't shipped due to the holiday, I ordered September 27, but no luck.

If I ever receive them I will let you know.

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Well its still golden week holiday. So many things are still on hold. I also ordered a Canon 50mm STM lens from here in USA and it too is on hold due to the holiday.

 

Expect shipments to go out on Monday or Tuesday.

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  • 3 weeks later...

An update on the 36W UV LED bulb idea.

Would I recommend this, No. But maybe yes.

 

I have a sense of humor, so now find the last week playing with this quite ridiculous.

 

I got my two 36W bulbs. They are heavy, much larger than I expected. It doesn't fit in my standard desk lamp, but does fit fine my E26/E27 sockets. Its mostly Aluminum, like just buying a heat sink.

 

Out of the box only white light, extremely dim and very hot. I ran a spectrum and the peak was 395nm with low intensity and spread out into the full visible. Had a good size 500nm peak.

 

So contacted the seller to return. Thats when comedy was born. I sent the image of the spectrum and said its not as advertised. There reponse was two fold. First they didn't believe me and wanted a video of the light and spectrometer to show its their light. And second in the same response, they wanted me to smash it to bits with a hammer and send them a photograph so they could refund me for the damaged item.

 

I kid not, to clarify many times this is what they wanted. Well I don't like solving problems by smashing them with a hammer. So I tried the video. But ebay doesn't let you upload videos. Then I noticed something interesting. The angle of the spectrometer probe to the front of the light significantly affected the peak max of the light.

 

The front lens of the light is a large single plastic disc, molded to fit over the leds and held inplace with a metal spring. I carefully removed the spring and the 91mm diameter front lens comes off fully exposing all the LEDs. And it looked like polycarbonate.

 

For those paying attention polycarbonate is used in our UV protection goggles.

 

Now with lens removed, its quite bright. The peak max is 375nm and the aluminum isn't quite as cooking and egg hot. The angle of the probe was catching different thickness of polycarbonate, which was filtering out all of the UV and sinking that energy to the massive aluminum heat sink.

 

The main board gets 46.3 Volts and I measured around each Led and they are 3.81 to 3.83V each.

 

It also provides bluer, but a stop more light (with lens off) than my Linda 7W 365nm led bulbs.

 

The sellee provided me with this plot for their LEDs in one of our many comical exchanges.

 

 

So if you have a spectrometer, and don't mind playing. Then its an interesting light. Filtering it will be hard though. I will have to think if I want to do that. You will have to make a custom holder.

post-188-0-27266300-1603783222.jpg

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...so they put UV-absorbing plastic on UV-emitting LEDs. Nice. Not all plastics absorb UV like that, I have some transparent plastic things (even like 2 mm thick) that are perfectly transparent even to light from my 340 nm LED (I tested this with a sheet of paper to see the fluorescence). So they chose one of the worst kinds of plastic for the dome.

 

It also provides bluer, but a stop more light (with lens off) than my Linda 7W 365nm led bulbs.

Bluer as a false UV-color?
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Bluer as in I locked in my white balance and compared the two bulbs head to head.

Thats expected as my Linda is peak max 370nm, with more 365nm curve area, than this bulb which float around 372nm, with some being 375nm. This spot goes more into 400nm as well. The linda is more tight and almost doesn't need any filtration.

 

The seller claims the glass infront of the Leds is PMMA. But since at 30 degree angle, absorbs UV. See image. This is crap, its not PMMA, it blocks all UV coming off the light.

post-188-0-90022400-1603832251.jpg

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So without it you have a ~180 degrees beam? It becomes a flood and no longer a spot?

 

You can place a Fresnel lens that doesn't absorb UV on top to make it more like a spotlight. If you want you can place a big glass lens, like the lens of a car headlight, they transmit 365 nm well but are heavy.

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Actually never was a spot. This lens spreads the light evenly out. Without it, the light is more tight, but still not spot light like.

It has the potential to be better than the Nemo, if a reflector could be made.

Its actually 0.35Amps x 3.83V for each Led. So about 16W real world.

 

Semple makes a paint on mirror paint that I am almost tempted to try. But it's expensive. But would be easier to make a reflector with it and a chunk of wood.

 

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How big would the reflector be? Like 20 cm in diameter? It would resemble a studio light like the ones used by photographers. Quite professional acutally. Imagine it on your desk firing down with the subject below.
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How big would the reflector be? Like 20 cm in diameter? It would resemble a studio light like the ones used by photographers. Quite professional acutally. Imagine it on your desk firing down with the subject below.

Thats a great point. The inner diameter is 91mm I might have a furnace tube adapter that would work.

I have been using 4inch to 3 inch furnace tube adapters to add 72mm filters in front of my desk lamps. One of the ones I have might work. They are stainless steel and you can easily wrap aluminum foil to make it shinier.

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