LIGHTFEBlack Light UV Flashlight 365nm Blacklight UV301D with LG LED Source,Black Filter Lens, Max.3000mW high Power for Resin Glue Curing Light, Rocks and Mineral Glowing,A/C Leak Detector

Who is this for?If you're curious about fluorescence (minerals, body fluids, terrestrial arthropods etc.) then this is the best consumer-oriented UVA/B flashlight on the market. The only place to go from here is even more specialized equipment meant for labs, and this generally means separate power supplies for wattages greater than 20W and prices *starting* at ten times that of this flashlight.How does it look?Three UV LEDs are powered by a custom triple lithium polymer battery pack. Two of these custom battery packs are included, each at about half charge. Their capacity is enormous and even with line power expect several hours for a full recharge. The LED-containing head of the flashlight can be taken off entirely and replaced with the dummy endcap. Putting this dummy cap on the open end exposes the charging ports on the base of the flashlight body, with a USB-C port for charging the battery and a USB-A port for discharging it to power a phone, e.g. There are two buttons, one for power and the other for selecting intensity. The flashlight can be locked, and prevented from illuminating, by pressing both at once for a certain length of time. It feels as heavy as a small handgun or large cordless drill and even though it has a lanyard I would not expect the nylon of this to hold up to a lot of swinging from the wrist. It's that heavy.What does it do?There are three intensity settings. In an interior space lit with many lights during the day this flashlight will fluoresce things from across the room on any of its three settings. At night or in perfect darkness indoors the effect is startling. You will see fingerprints and handprints on painted walls, huge numbers of them near highly-trafficked areas. If your drinking water has any concentration of iron or iron salts every surface in bathrooms will glow from the deposited metals. You will see fluorescent lint in several colors on every fabric surface and most smooth ones. This lint has been coated in the fluorescent chemical that laundry detergent contains to make white clothes fluoresce subtly in sunlight, making them appear cleaner than new.In some ways surfaces that do not fluoresce at all are more interesting than those that do. Porcelain cups or china plates generally do not have fluorescent glazes and these, when the flashlight is put on them, have a very deep and monochromatic purple color. It's startling to see white china become as darkly purple as if you had coated them in machinist's layout fluid. This is the very deep purple color of the Wood's filter and represents the most extremely violet light produced by the LEDs. This light is so next-door to UV-A, which is invisible, that it has a not-quite-there quality and lends this ghostliness to things it shines on.Human skin, particularly one's own, is also startling. Firstly because the beam feels like direct sunlight even though the total amount of visible light is in the arena of 1 watt. Age spots are greatly enhanced and even freckles that disappear during the winter are revealed in greater-than-summer contrast. The different bacteria that live on skin are shown, with those in hair follicles being a very striking orange.The visible light from the flashlight is greatly attenuated by the Wood's glass filter. Without anything fluorescing significantly it seems to be perhaps a watt or two of visible light (much less light than a single christmas tree bulb.) But placed over something fluorescent, like a glass of tonic water, there is very suddenly about as much light as a 20 watt bulb. This effect is very striking because it appears to violate the brain's way of interpreting cause and effect.Despite the fact that 20 W of UV light is a lot for a handheld device, 20 W lightbulbs are not very bright. It is therefore easy to wish even this huge amount of UV light were greater because the only thing to compare it to is not other UV flashlights, but those built specifically for visible light. And these, especially anything in this pricepoint, are many times as powerful.***Eye Protection***The cornea of the eye readily absorbs all wavelengths of UV light. This is done to save the retina from damage and protect the ocular jelly from becoming cloudy. However the cornea is transparent and poorly supplied with nutrients and blood. This means that damage done tends to accumulate. This is what cataracts are, and why elderly people are most affected by them. At any setting this flashlight will absolutely produce cataracts in the long-term and something like snow blindness (corneal sunburn) in the near-term.Window glass/flint glass absorbs almost all hard UV (UV-C) and around 60% of the wavelengths that pass this flashlight's Wood's filter (UV-A and UV-B.) This means that eyeglasses with glass lenses are not enough protection. Polycarbonate is a much better absorber of UV light. However even eyeglasses with polycarbonate lenses are not enough protection, as your corneas are still exposed from the side. Polycarbonate safety glasses with wraparound, one-piece lenses are the best solution. Anything made of polycarbonate will filter nearly all the UV light produced by this flashlight, or for that matter the Sun.The bottom line is that anyone using this flashlight and anyone in the presence of its use needs full eye protection made from polycarbonate plastic.Is it well made?Yes. This is at least as well made as a rifle scope, high-end handtool or pro kitchen equipment. The threads are all greased with Vaseline and the rubber gaskets seal well in their glands. Wood's glass is loaded with metals and is therefore much more fragile than even untempered windowglass. Because of this the filter is very likely to break if the whole flashlight is dropped. That said, every other component appears to be robust enough for heavy use. This flashlight comes in a small and cheaply made hardcase with adequate, low-quality foam padding.The first time I bought this flashlight one of the diodes had a manufacturing error that made it illuminate only about a third of its area. The return was handled by amazon and a replacement (a-ok) was sent as soon as the defective one was in the mail. The total turnaround from noticing the defect to holding the replacement flashlight was 4 days. If you're curious about this problem in your own flashlight you can hold it close to a flat surface and look at the shape of the three blobs of light cast there. Good diodes should cast roughly square blobs of light. Defective diodes will show patterns that differ from the other two. This is also visible by looking directly into the head with protective glasses on but it is no better at verifying a defect than the indirect method, and should be avoided as a matter of principle.

This is by far the most powerful 365nm flashlight I have used. None of the others come close to it's brightness, even with the black light lens filter affixed to it.Let's go over the pros and cons and then go into more details.Pros:* Extremely powerful true black light flashlight.* Included black light filter prevents visible light from escaping the flashlight.* Water resistant.* Extra battery pack included.* Hard plastic padded case included.* Separate power and mode switches.* Can recharge from any USB power source.* Includes USB power supply and USB cable.* Built like a tank. Very heavy duty.* The flashlight can also be used to charge a cell phone!Cons:* Expensive. (But it's very high quality, and there's no cheaper alternative I could find that is even half as good.)* No zoom function. (Almost decided not to get it for this reason.)* Light projects a beam with a very bright center spot, instead of a smooth evenly lighted beam.* Unusual battery configuration requiring a special built-in charger.* DANGEROUS. This is a con for all similar UV lights. This can cause sun burn if you point it at your body for too long, and can also cause blindness if you look at the light directly without protective UV glasses.The black light filter does an amazing job. It's not a cheap filter. Because of the black light filter, there's almost no visible light seen from the flashlight. This makes it easier to spot things that are fluorescing. Using high quality UV protective glasses (don't try this without them!), you can actually look directly at the flashlight, and you'll see a black lens, and only 3 very small faint violet LEDs inside it, and virtually no visible light leaving the flashlight. However there's tons of UV light that you can't see that's coming from the flashlight, and so wear protective UV glasses when using the flashlight!When at it's full brightness setting, it will actually illuminate black light reactive objects in full daylight. It's that bright.The light range actually is much wider than 365nm. 365nm is the flashlight's peak. It will fluoresce things down to the point of the black light filter's cutoff frequency, which is something like 385nm. So it will work for a wide range of fluorescent material.The flashlight has a fairly large beam, and a very powerful center spot which is a much smaller radius. I'm not a fan of this. I prefer a smooth beam from perimeter to center with a zoom lens.The flashlight comes with a hard plastic protective carrying case with foam cushioning inside that can store all included items.You get 2 sets of triple 18650 battery cells for a total of 6 18650 cells. That's one reason for the very high price of the flashlight. These batteries are not cheap. They are not normal 18650 cells, these are 3 batteries combined into 1 single large cell. Unfortunately, you cannot charge these with a normal 18650 battery charger, since they are the size of 3 batteries, and have a special shell around them that can't be removed.This is overall a great UV flashlight. It's top of the line, with a lot of good features.HIGHLY RECOMMENDED! But, KEEP THIS AWAY FROM CHILDREN!

This is the UV301D flashlight, nominal 365 nm wavelength. When I opened the box I read the brief manual and then tried to turn it on but got nothing. Tried replacing the AA battery, still nothing. Explored manual again. Figured it was defective and not expensive enough to be worth returning, I started taking it apart. Immediately behind the LED assembly I found a strip of paper folded into 3 layers, preventing electrical contact. When I took it out and unfolded it I found one end had an instruction to remove it before use. I can't find any reference to this anywhere. This isn't visible if you remove the rear end cap as you typically would to replace the battery, so it was a fortunate accident that I found it. I give them 4 stars instead of 5 for this reason, but I almost gave them 1 star and said "it didn't work".Now it works great. The filter does a good job of blocking visible light, so, unlike my other UV flashlight, it does not cast much visible light but it causes objects to fluoresce brilliantly, like a Woods lamp. Now that it works I am very pleased with it.