School me on UV

I've got no experience wih UV flashlights and searched the web for a guide of some sorts. A lot of bits and pieces info, but nowhere could I find a comprehensive guide. What I would basically like to know is what wavelengths is used for what, different power outputs, etc.

Can't give you the worlds most info, but what you do want is a 365nm up light. This is the UVA spectrum and is what you think of when you think UV or black lights. Cheap us lights typically employee 395-405nm emitters that do not properly fluoresce objects like a proper light will.

a good starter UV light is the convoy s2+ 365nm

Thanks. My noob understanding is that different types of objects (bugs, body fluids, currency markings, etc.) all fluoresce at different wavelengths. Is this correct?

Many suppliers advertise 3Watt or 5Watt for example. Is this the range (throw) equivalent of normal lights?

One pf the best brands for UV LEDs is Nichia, the 365nm emits almost no visible light and has a very good efficiency

the Convoy with 3W Nichia is really good the LED is rated to radiate 780mW of 365nm UV

It can make things light up no other cheap UV LED can do, of course there are some other brands of good UV LEDs

Ok, slowly learning.

On your second point: does this mean that 780mW of the 3W is at 365nm? Basically an efficiency?

From the spectrum graphs it appears that visible light starts at around 400nm. Would a 395nm light emit some visible light already or is it a sharp changeover to visible at exactly 400?

FDP said:

Ok, slowly learning.

From the spectrum graphs it appears that visible light starts at around 400nm. Would a 395nm light emit some visible light already or is it a sharp changeover to visible at exactly 400?

Click to expand...

No two people have the same sensitivity to the spectrum of visible light. I have never heard of anyone being able to directly see by UV, so a true 395nm light would be for the most part invisible. Since current LEDs can't be tuned that closely, there is some bleed-over into the visible light spectrum, which for most people starts around 400nm. Using a 365nm or shorter emitter will be for all intents and purposes invisible to the naked eye. As Lexel said, at 365nm there will be a slight purplish bleed into visible light, but anything shorted will be invisible. That is the problem with hard UV lights (shorter than 365nm). It is quite easy to wind up cooking parts of one's eye without realizing it if one is not careful.

And yes, different materials fluoresce best at different wavelengths of UV, based on their material makeup. But until one gets into much shorter wavelengths than most hobby lights are capable of, there will be some fluorescence from any wavelength in the 'soft' UV range.

Unless you're doing auto repair or have no pets, do not get a UV as looking around your house will reveal so much more than you ever wanted to know.

I own the Convoy S2+ 365, and while the Nichia LED is rated at 3 W max, in the Convoy it is driven at around 750 mW.
When holding the light close to your hands or lips, you can feel quite a lot of heat coming from the LED. The head will get warm after running a couple of minutes.

The LED itself gives off a faint deep blue glow, and unless the UV hits something fluorescent, you'll have a hard time telling if it's on or off, especially in reasonably lit places.
When the UV hits something fluorescent, you'll be surprised at the brightness of it, and only then you'll start to realize how bright it is in UV.

At around $25 or 22 euro, this is the best starter UV light you can get.
But don't forget: It runs on 18650 batteries.

And as Redvalkyrie said: This light is perfect for spotting filth in your house.
I once read a story about a guy who bought an UV light while staying in a hotel, and after he tried out the light in his room, he slept that night in his clothes on top of the bed covers.

Thanks for all the info so far!

If you want to eliminate the visible part of the LED spectrum you can use a UV filter.
I ordered a week ago 10 ZWB2 filters cut for flashlights as minimum quanitity and will sell the other 8.

The convoy S2+ runs the Nichia LED at 3W electrical
depending on the LED efficiency you get 600-900mW UV and 80-90% from it below 370nm,
thats at least 10 times more than the cheap 3W electrical 365nm did
and it doesnt emit some white light like no name ones do, all you see is some purple

the contrast between visible light and fluorescence counts

I added a photo from a no name 3W 365nm LED, you can see the white wastelight from it
and because of the few mW output below 370nm you can see the deep UV signs slightly
the camera has same settings on manual than the picture a few posts earlier

Stay out of the kitchen, bedroom, and especially the bathroom with that UV light.

I've got small children! I want to verify their toilet aim....

I have the Convoy S2+ UV light. It's well made and very effective.

Make sure you have proper eye protection when using UV lights. See here.

Most common wavelength of UV LED is 365nm and 395nm, but the price is variety from $-$$$ according to it performance and place of origin. The most expensive UV I've used is about $150 for one LED. It's a customs light for underwater photography lighting.
Ps. 365nm is 5W, 395nm is 3W.

Do you have some more info on this? - 365 vs 395 power? Why can't you have a more powerful 395 for example?

He is talking about the electrical rating of the LED
but just one mo name China 3W LED can be very dim while another high quality brand LED is really bright

For consumer products usually 3 or 5W elecrical power is used
To make sure yo get best performance stick with LEDs like Nichia, TaoYuan, LED Engin, Lite On, Luminous Devices or Everlight

technically a LED with same power consumption is more efficient on higher wavelengh

for example one of the best single emitter LED is rated 18.9W electrical
in 365nm it has average of 3.6W optical output
In 385 and 405nm its rated 4.6W optical output