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I wonder if anyone might have any ideas on this please? I have been shooting some short duration flash images for a new book, of tonic water being poured into a glass. Every image has a red catchlight, whatever the position of the flashes, even those shot without the pouring. Technical details: 2 x Metz 45CT1 flash guns with UV absorbing window removed, and replaced with one half of an old Kodak 18A "Wood's Glass" filter (I have checked, this is light tight) Camera: Nikon D800 with 105mm micro-Nikkor. 1/160th @ f/11. Flash duration approx. 1/2,000th second. Thanks for looking!

With the increase of more sensitive sensors, the question of taking photos of living insects has slowly wormed its way into my mind, and triggered by Stefano's thread (https://www.ultravioletphotography.com/content/index.php/topic/4435-some-bees-on-dandelions/ ), I'd like to ask the question of how to take UV-photos of bungs, flies, bees, etc., and not hurt them. This, of course, under the assumption of using some sort of light source in addition to the sun. In my case, I'm thinking of the Yongnuo YN560-III flashgun with the protective cover removed, turning it into a full-spectrum light-source. I don't know exactly how full its spectrum is, but there's plenty of UV in it. In order to keep ISO not too high, I had to usually use it at half-power or higher when taking photos of plants. I remember reading about this in an older topic somewhere here (can't find it now), with the suggestion of using flash once on an insect ought to be ok. On other sites I've read that using a flash directly on the eyes of a butterfly might easily blind it (that was about VIS-flash, but full spectrum will be even worse, I guess). I wouldn't want to blind an insect just to get a photo of it. So, how are the other members here handling this? Is there some reliable data of how much light (in candela or any other unit) is acceptable?

Today I chanced across my old, failed harddrive, which I had set aside in order to take some photos, and decided to give it a go. I used my usual cameras: VIS: Canon EOS 5DSR IR: Canon EOS 6D, converted to 700 nm FS+UV: Canon EOS 6D, converted to full-spectrum As lens I used the EL-Nikkor 80mm f/5.6, set at f/16 throughout. Most of the photos are at ISO 100, only the UVIIRF is at ISO 800, and the UV with UV-LED is at ISO 200. For the UVIIRF I still had to use 30s as exposure time. As is evident from the shadows, I didn't put the torches or the flash on a tripod but handheld them, so the angles are not completely the same, which I don't expect to make any real differences. What do you think? I find it interesting how the circuit paths appear and disappear, and I'll definitely have to check out the glowing bits in the UVIIRF. First, VIS-camera, room lights (Standard Osram LEDs with 2700 K) for lighting: Next, VIS-camera, Nemo-torch (365nm): : FS-camera, without filters, room-lighting (Standard Osram LEDs with 2700 K): FS-camera, without filters, full-spectrum flash (Yongnuo VN560III with the cover removed): FS-camera, without filters, Nemo-torch (365nm): FS-camera, UV-filter by Makario, full-spectrum flash(Yongnuo VN560III with the cover removed): FS-camera, UV-filter by Makario, Nemo-torch (365nm): IR-camera, room-lighting (Standard Osram LEDs with 2700 K): IR-camera, full-spectrum flash (Yongnuo VN560III with the cover removed): IR-camera, Nemo-torch (365nm): IR-camera, LED-torch 850nm: IR-camera, LED-torch 940nm:

Greetings from Mount Vernon, Washington, USA! I am grateful to have been introduced and accepted into your community! I am interested in all things light and its use in application. My education is BSEET/ABET from DeVry Institute of Technology, Phoenix 1999. I have eighteen years of engineering and technician experience in the following industries: Industrial Nd:YAG lamp and diode pumped laser markers from 3-100 W at IR/Green wavelengths of 1064nm and 532nm (rofin) Semiconductor stepper & scanner photolithography at UV/DUV wavelengths of 365nm, 248nm, 193nm, and 157nm (ASML USA/Veldhoven at Motorola, TSMC, Texas Instruments, Micron, and IBM) Aerospace metrology laser and radar trackers (Janicki Industries) Commercial HVACR R&D full life cycle product development testing for manufacturing (Legend Brands/Dri-Eaz Products) I look forward to working with you to progress the art and science of Ultraviolet Photography! Create a Great Day! Aaron

Here is a pumpkin (or in some parts of the world, a squash) using Laser-Stimulated Fluorescence (LSF). LSF was described in my first post on it back here. Please reference that post for the procedure and background, safety requirements, and equipment used. Camera was the Sony A7S (modified). Lens was the Nikkor 20mm/3.5 (which I haven't tested in UV reflectance). Filters on camera were the Tiffen Haze 2E + BG38 2mm. 30 sec, F/16 (for depth of field reasons), ISO400. White balance altered to suit taste.

Camera: Df Lens: Zeiss 60/4.0 UV-Planar Uvir Block: Baader UV/IR-Cut Filter UV Light: Nichia UV LED Haiku Flashlight, 033A Diode All Photographs: ISO1600, Neutral Picture Control, in-camera Auto White Balance later reset in Photo Ninja converter, made in total darkness. The camera recorded these photos in the blue channel. In the editor I tried to re-produce the violet colour as best I could. ADDED 27 Feb 2015: These photos need a tiny bit more blue in them to match what I saw with my good eye. But not so much blue as to make the spoon look "blue-violet". I do not have a name for the colour I can actually see. Perhaps "magenta-violet" describes it? I cannot get rid of the visible light leak on this Nichia torch. Either the Baader-U or the Hoya U340 on the torch does help cut it some. 1. Violet light leak, Uvir-block filtered lens, unfiltered Nichia torch. f/4 for 1.6". 2. Violet light leak, Uvir-block filtered lens, Baader-U on Nichia torch. f/4 for 1.6". 3. Violet light leak, Uvir-block filtered lens, Hoya U340 on Nichia torch. f/4 for 1.6". ********** Just for grins, here is the spoon photographed with Violet UV-LED illumination. 4. Uvir-block filtered lens, violet LED. f/4 for 1.6".

I was looking at some 365 nm UV LEDs on Mouser, a website that is available in Europe for sure, but I don't know if you can buy from it in the US or other countries. From what I understand, it is a platform (like Amazon or eBay), where you can find items from various manufacturers, like LED Engin, Luminus Devices, Texas Instruments and so on. You can find LEDs, photodiodes, ICs, power supplies and in general electronic stuff. I have no affiliation with Mouser or the individual manufacturers. All LEDs emit at 365 nm. I will not say it every time, since it would be repetitive. If you don't know how to properly drive an LED, see this topic: https://www.ultravio...-power-to-a-led I suggest you to read the datasheets of the LEDs for more information. I will only report some of it. https://eu.mouser.co...252BksMHA%3D%3D Manufacturer: LED Engin Datasheet: https://eu.mouser.co...020-1915176.pdf This is a 10 W LED consisting of 4 chips, similar to mine, but without the lens. The chips are wired all in series (4S configuration), while my LED is in the 2S2P configuration. This way the current is the lowest and the voltage is the highest. Also, you can be sure each chip gets the same current. If you read the datasheet, there are two output power bins. The T bin has the lowest output power. I guess it is the least efficient version, and it seems this is the version they sell. But then they state the typical output power at 700 mA, which is 4.1 W. Typical values (at 700 mA): Forward current: 700 mA; Forward voltage: 15.2 V; Input power: 10.64 W (calculated by me from the data above); Output power: 4.1 W; Efficiency: 38.53% (calculated by me from the data above); I wonder if an LED in the U bin can reach 50% efficiency. Note that you can drive this LED at 1 A of current (read the Absolute Maximum Ratings), but it is probably near saturation and the efficiency will start to drop. It isn't really worth it to overpower it, in my opinion. They sell also the chip alone: https://eu.mouser.co...v723tzyvw%3D%3D https://eu.mouser.co...GJAh68Jv%2F0%3D Manufacturer: Luminus Devices Datasheet: https://eu.mouser.co...eet-1504881.pdf This is a pretty powerful LED. Luminus Devices claims over 20 W/cm2 of irradiance, which is more than enough to burn things (if you really like to do that). Be careful, don't operate it with something sitting on top of it, it will burn it! This LED has 12 chips connected in a 4S3P configuration. This version is currently non-stocked. This LED is quite expensive, but seems to be a very good one. Typical values (at 2.25 A): Forward current: 2.25 A; Forward voltage: 13.4 V; Input power: 30.15 W (calculated by me from the data above); Output power: 10.6 W; Efficiency: 35.16% (calculated by me from the data above); Note: you can drive this LED up to 4.5 A. It is not at all saturated at 2.25 A, you can really push this little beast at more than double than that (see datasheet, page 6). LED alone: https://eu.mouser.co...mKhxM42878sY%3D They sell them on other supports (code starting with CBM) but they are a slightly different version (H365 instead of I365). https://eu.mouser.co...51vy334UA%3D%3D Manufacturer: Inolux Datasheet: I can not put a working link. Click on it from the first link. This LED is special since it has a really narrow beam of 30°, although the cut-offs don't seem to be very sharp. A narrow beam angle means it is easier to collimate it using a lens, without wasting light. You will not need a very thick lens with a short focal length, but a more common, flatter lens will work. Of course you don't need a narrow beam angle to collimate a light source, but without that you will waste a substantial amount of light to the sides, lowering efficiency. Don't use this LED with a parabolic reflector, as it will simply "avoid" it, like if it wasn't even there. The LED is unmounted. Typical values (at 1 A): Forward current: 1 A; Forward voltage: 3.7 V (calculated by me as an average between the minimum and maximum voltages, as they don't specify the typical voltage); Input power: 3.7 W (calculated by me from the data above); Output power: 1.6 W (read from the first link, not from the datasheet); Efficiency: 43.24% (calculated by me from the data above); For now, that's all. There are a lot more LEDs you can find there, IR ones too. Just search.

Today, out of curiosity, I tried to see how deep my camera can see in UV. I took my 340 nm LED, a diffraction grating and wanted to see if the spectrum extended further than the one from a 365 nm LED. It did work, but the result wasn't very precise. In fact, a diffraction grating is approximately linear for wavelengths significantly shorter than its pitch, and Andy and I discussed this here: https://www.ultravio...post__p__31708. I had two things to do: find a nice exact formula to calculate the wavelength of something by counting the number of pixels in an image (you will see later) and something with a very precise and known wavelength to use as a reference. Let's start with the reference: I have a CFL bulb. These bulbs emit both mercury lines and phosphor lines. I don't know the wavelengths of the phosphors emissions, but I know very well the mercury lines. So I use two books (as usual) to make a slit, mounted my UV-pass filter (ZWB2 (2 mm) + chinese BG39 (2 mm)) on the camera and a diffraction grating on top. ISO 1600 and +2 exposure compensation weren't enough. So I put the camera in "scene" mode and shot some ISO 80, 60 seconds exposures. And this time it worked wonderfully. The last image looked like this: Notice that in "scene" mode I can't white-balance, and those are "RAW" colors. Crop: See? There are two big lines. The blue one is the 404.7 nm H-line and the pink/orange one is the famous 365.4 nm I-line. So I had two references. In Paint, I measured the distance (in pixels) between the center slit and the two H-lines. I was surprised by the consistency of the results. The first distance (left line-center slit) is 1473 pixels. The second one (center slit-right line) is 1475 pixels. The average is 1474 pixels. To be sure that that was the H-line I took a visible spectrum image. The colors are funky because I had a UV white-balance on (I didn't use the "scene" mode, because I would have overexposed massively): You can also see the 546.1 nm green line. I tried again to measure the distances in pixels of the H lines, but got much less consistent results: 1462 and 1499 pixels. The average is 1480.5 pixels, which is close to the previous average but not quite. Maybe the different focusing (because of the focus shift between VIS and UV) altered the magnification? Anyway, I was now sure that the first line in the UV shot was the H-line. I measured the distances of the I-lines from the center slit and they are even more consistent: 1320 and 1319 pixels, whith 1319.5 pixels as average. Doing a simple proportion, assuming that 1474 pixels correspond to 404.7 nm, you get 362.3 nm, which is close but not as close as it should have been. The problem is that diffraction gratings are not linear. It took me a while to figure out a proper formula, and here it is: (for reference, see here: https://www.ultravio...dpost__p__31725) I know that, and that, so, where x is our displacement in pixels and L is the distance between the diffraction grating and the wall. But we don't have it, and so we have to calculate one. It sounds strange, but to make things work we have to imagine a distance in pixels between the camera and the imaginary wall the lines are projected on. To calculate it, I used the known data from the H-line: With x = 1474 pixels. And that gives us our final formula: Where x, to be clear, is again the distance in pixels between the center slit and the lines. Note that this formula will work only for me and my camera used at the same zoom. You can make your own for your camera, you just need to change L. Doing again the calculations for the I-line, we get, which is closer. Not perfect, but closer. Here one pixel is about 0.28 nm.* Now the spectrum with the 340 nm LED: Again, "scene" mode and "RAW" colors. This time I measured the distance between the left and right extremes of the spectrums (the shorter wavelengths visible in the image), and divided by two. The middle point isn't exactly in the middle, where the LED is, but offset to the right by about 7 pixels, that is similar to the visible light image before, but doing the average I should eliminate the error (in theory). Displacement: 1223 pixels. Wavelength: 344.7 nm. ...so, apparently my camera can still record a tiny bit at ~345 nm? That's quite deep, but if I didn't mess up somewhere, that's the limit. The LED should peak between 340 and 345 nm, so I can't see the peak. If you do what I did, you can measure the cut-off wavelength of your camera, and the peak wavelength of LEDs and stuff. If you want to measure above or near 1000 nm, use a diffraction grating with less than 1000 lines/mm. 500 lines/mm will work. *corrected after posting.

Since I'm doing the Queen Anne's Lace by every method lately, here is the UVIVF, which was startlingly pretty. The main technical component here was an attempt to subtract off the background light since the plant was slightly illuminated by street lights. I took two batches of photos, one with the 15W UV torch (hereafter called "the Nemo") and the other without it. Then I averaged both separately, and subtracted the two pics after averaging to remove the noise. Since the only difference between the two is the UVIVF and/or any contamination from the torch, the hope is that it will remove the effect of the spurious lighting. I think it was mostly a success, since the background became quite black. The camera setup was essentially the same as in the previous zinnia thread. Visible reflectance, illuminated by streetlights. This is the averaged photo. I also adjusted exposure to make the scene visible (it looks black otherwise with the original exposure settings). Also (for display purposes, but not in the image subtraction), I white balanced on the outer petals. 30 photos x F/8, ISO500, 1/4" UVIVF + streetlights 38 photos x F/8, ISO500, 1/4" UVIVF after subtracting streetlights in Photoshop (UVIVF + streetlights) - (streetlights) = UVIVF hopefully Crop on the UVIVF: 1-1 Crop of the visible: 1-1 Crop of the UVIVF: I will say, the averaging really drives the noise almost to nothing. Since the Starry Sky Stacker program has tools for evaluating image quality and accepting/rejecting each photo individually before stacking, and the camera takes all the photos in a batch, the actual time for taking and processing these photos was about an hour start to finish. There is no reason not to employ this procedure for almost every photo I take of stationary subjects, in fact, because the quality improvement is so dramatic.

Last night I took some photos of this flower, which looks something like a coneflower. [Edit: It is a zinnia. Thanks, Andrea!] I tried a new method for processing. My previous attempts at shooting flowers in-situ have had issues with flower movement from wind, so this time I decided to try taking multiple images with high ISO and short exposures to maximize the chance of getting a sharp image, then throw away all the blurry ones and stack the rest to reduce noise. First a visible photo. This was taken with the Sony A7S converted camera, a Hoya UV/IR cut (which transmits UV up to 380-390nm or so) and the LED on my iPhone (which probably doesn't emit much UV). I subsequently corrected the colors using a Color Checkr Passport in Photo Ninja. The lens was the EL-Nikkor 80mm/5.6 metal. Visible reflectance photo F/8, ISO1600, 1/100" -- Onward to the UVIVF. These used the Daylight white balance setting on the camera for white balance. This was chosen simply because other people on here have used it and I don't know what else to do. The torch was the new 15W torch from eBay (we NEED a better name for that thing!) and I forgot to remove the glowing ring, although I don't think it affected the results much because the torch was ~0.5-1 meter from the flower. The torch was unmodified. Next, 30 photos were taken with the torch on, of which 16 were usable (sharp). I also took another 30 "dark frame" images so that the stacking software would remove any remaining visible light from the scene. (The flower was in near total darkness, so these frames appeared black.) These images were taken automatically for me using the Sony TimeLapse camera app, which they sell in their app store for $12US. It is essentially a built-in intervalometer for the camera. The images were then stacked using the Mac program Starry Sky Stacker, intended for astrophotography purposes, but well-suited to dealing with moving blossoms also. I chose to take the arithmetic mean of the images, as opposed to median, 60th percentile, or max value, which are other options in that software. Final post processing involved a small amount of denoising with Neat Image plugin for PS, and sharpening with SmartDeblur applied to the center of the flower. Only the disc/cone in the center of the flower was sharpened, leaving the petals unsharpened. UVIVF, whole frame (reduced size) F/8, ISO1600, 1/10" x 16 images 1:1 crop [ETA: the color profile was messed up on this one, reupload is below with proper profile] F/8, ISO1600, 1/10" x 16 images ETA: here is a reupload using the original color profile. Overall I would describe this as a very successful experiment, and definitely I recommend the stacking method for dealing with flower motion.

I am thinking about converting a Yongnuo YN660 (Xenon bulb) as per Dom's video , by coincidence I already have three of these flashes and the wireless trigger. However to be safe I would probably buy a new one, so it can be done straight out of the box. I also do sometimes use all three for some setups, so would like to keep them unmodified. Being located in the UK, I wonder whether there are any less expensive filter options for me? As I haven't found a UK supplier of the Hoya U340 77mm and the other filter to block the IR leakage, I haven't checked but I'm not hopeful. The 'window' on the YN660 is about 70mm x 35mm, has anyone tried using two smaller filters side by side in such situations?

I've been exploring the world of microscopy more recently, and of course wanted to do some UV microscope images. The image below is a sunscreen product - an oil in water emulsion, with the UV absorbing ingredient in the oil phase - on a microscope slide, lit with a Xe lamp and imaged with a UV converted Nikon d810 camera. Overall magnification about 400x, so the oil droplets start at under a micron in diameter. The oil droplets contain the sunscreen, hence look dark. I've written up more about it here - https://jmcscientificconsulting.com/uv-microscopy-of-sunscreen-formulations/ - including a rather funky UV video of when the emulsion collapses and the oil droplets fuse together, filmed at ISO 10,000... Logistically it was not easy to do - the microscope needed supporting on a lab jack, to get the light port up to the same height as the output from my lamp. Cue the health and safety violations.....

I tried to photograph a 23 W "cool daylight" 6500 K CFL bulb, as I wanted to see how much UV they emit. I knew they do emit some, but I wasn't expecting this. Camera: Full spectrum Panasonic DMC-F3, filter: ZWB2 (2 mm) + chinese BG39 (2 mm). F-stop: f/2.8, ISO 400, 1/8 s exposure. F-stop: f/3.1, ISO 400, 1/8 s exposure. Since I already had a UV white balance set in-camera, that's how the bulb appeared on the camera screen. I thought for a moment I forgot the UV-pass filter, since it looked like a visible light image, but the filter was in place. That was UV (and quite a bit of it). Polycarbonate goggles (blue) and 2 mm ZWB2 (yellow). F-stop: f/3.1, ISO 1600, 1/8 s exposure. Are we sure this things are healthy to look at? An LED bulb emits basically no UV light, and the little they emit is above 380 nm. Here I probably have the 365.4 nm I-line as well as some "blue UV" (I don't think I am seeing the 404.7 nm H-line).

Following on from the post on compact fluorescenct light bulbs (here - https://www.ultravioletphotography.com/content/index.php/topic/3909-compact-fluorescent-lamp-uv-emission/page__view__findpost__p__35797), I thought I would measure the irradiance spectra from two light bulbs; Old style 60W tungsten filament (of which we still have a few in the house) 11W compact fluorescent light bulb (this is probably over 5 years old, as I tried it once and hated it, so put it back in the box) Spectra were measured on my Ocean Optics FX spectrometer, with a cosine corrector on the fiber, and calibrated for absolute irradiance. Probe tip was 1cm from the bulb surface. The 11W CFL was on for about 2 mins before measurement. Two plots shown below, but it's the same data. Firstly, at the scale to show the 11W CFL spectra. And secondly, zoomed in so the 60W filament bulb spectra can be seen more clearly. There's certainly a good strong 365nm peak in the CFL spectra, but I didn't see anything below that (although the spectra stops at 300nm here, I measured down to 250nm). No UV with the 60W filament bulb. I hated the 11W CFL bulb when I tried it. Amazing, the gaps in its output. Quite glad it went back in the box now.

As some of you know, I'm a big fan of Culture Hustles black paint as it shows good absorption in the UV, and I've used it for a number of my builds. They recently released a white paint, and I got to wondering whether it could be mixed with black to create white balance targets for UV. As it turned out, it wasn't great for that as its reflectance in the UV was very different to the visible. However I also tried using the Black 3.0 paint by itself, and the Black 3.0 paint mixed with magnesium oxide powder to make a grey target. These were compared against a Spectralon 10% diffuse reflectance standard. I've written it all up here; https://jmcscientificconsulting.com/uv-white-balancing-photos-with-culture-hustle-black-3-0-paint/ End result, the Black 3.0 paint and the Black 3.0 paint mixed with magnesium oxide worked very well and gave almost identical results to the Spectralon target for white balancing in the UV. Could be useful if you're looking for a darker target than the usual PTFE ones. Link to the latest version of the Black 3.0 paint: https://culturehustle.com/products/black-3-0-the-worlds-blackest-black-acrylic-paint-150ml

I have been thinking about this for a while. Since high (mains) voltage incandescent and halogen lightbulbs have been banned in most countries (and will be in all of them in the near future), and more and more people are switching (and must switch) to LEDs and energy-efficient lightbulbs, will tungsten-based light sources disappear completely in the near future? If I understood correctly, low voltage (12 V) halogen lights are still legal in the EU. Also, some special lightbulbs, such as those made for ovens, must be incandescent, since you can not put an LED or a CFL bulb inside them (just the idea of a CFL in an oven is nasty for me). Car headlights and stop/position lights are still commonly halogen and incandescent respectively, but more and more people are switching to LEDs and HIDs, even though tungsten ones are still perfectly legal. Will the demand for halogen lightbulbs drop so low that no company will be interested in manufacturing them? Will they disappear completely? Yes, they are inefficient and they don’t last long. Everyone knows it. But they produce 100 CRI light, that is similar (to some extent) to natural sunlight. They are actual blackbodies, and pretty hot ones (tungsten can be pushed to more than 3400 ºC). They produce almost the same exact light a red giant produces (same temperature). Just add Fraunhofer lines, some broader absorption by something else, and you are done. They produce a continuous spectrum, from UV to IR, and no LED can do that at the moment. Low-voltage halogens have a compact filament and can be pushed to higher temperatures (I have 12 V ones that I run at 16-18 V. They will probably last only tens of hours if used this way, but it’s worth it). That’s why I like them. I have 6 12 V 50 W downlights (4 with a vertical filament, 2 with a horizontal filament), 2 12 V 50 W capsules, a bunch of car headlights, a bunch of stoplights, some 6 V ones, 2 tiny 12 V 1.2 W capsules, a 230 V 25 W incandescent oven bulb, and some other stuff. I don’t lack tungsten sources. Their spectral bandwidth is still unmatched and, most of all, they are real blackbodies (as mentioned before). What do you think about this?

WARNING WHAT I DID SHOULDN'T BE REPLICATED OR ATTEMPTED UNLESS YOU REALLY KNOW WHAT YOU ARE DOING, AND YOU WEAR SAFETY GOGGLES AND SKIN PROTECTION. INTENSE UV RADIATION, EVEN IF IT IS UVA, CAN AND WILL HARM SKIN AND EYES. Hi, Here I will be talking about a 10 W, 365 nm LED. This LED is efficient, small and VERY powerful. I found it on ebay. The seller claims a 10 W power consumption and an impressive 4-4.8 W power output. That would mean a 40-48% efficiency, which is a lot for a 365 nm LED, although efficiencies of 30-35% have been achieved. The seller also claims that this is an LG LED, and that it has a quartz lens. The lens gives this LED a 60° beam (an LED emits an almost 180° wide “beam” without optics to narrow it). The LED is actually composed of 4 chips, in a 2S2P (2 rows in parallel each composed by 2 chips in series) configuration. Having said this, this LED produces a LOT of UV light. The seller recommends a forward current of 1-1.4 A, and I usually run it at 1.3 A. The LED is saturated at that current. I tried to run it at 2 A, and the output pretty much stayed the same. It requires 7.5 V to pass 1.3 A in it, so the power consumption is 7.5*1.3 = 9.75 W, very close to the rated power. As almost all 365 nm LEDs, it emits a bit of yellow-white light, and if you want a pure UV output (you need it for UVIVF, for example), you have to filter it. Needless to say that you need an heatsink to dissipate the (theoretical) 6 W of wasted heat. In my case, since I treated this LED as a “guinea pig” for my experiments, I only attached it to an heatsink with rubber bands, without screws or thermal paste. It still dissipated heat quite well, but you should use thermal paste to do that. I have a new one, still unopened, that stayed in a drawer for months, waiting to be properly attached to an heatsink. I used this LED to burn things, and this is not recommended, since smoke will deposit on the lens, heating it up because of the absorbed light. Even a 5% absorption means 200 mW of power converted into heat on a 5-6 mm lens. When it was new, the lens didn’t heat up (it was cold to the touch immediately after the LED was turned off). Later, it heated up considerably. So, how powerful is this LED? At 15 cm (6 in), I can feel heat on my lips and face in general. At 10 cm (4 in), I can feel heat on the palms of my hands. At 5 cm (2 in), normal, clean white printer paper reaches 33 °C (91.4 F). At 2 cm (0.79 in), the same paper reaches 80 °C (176 F). At the same distance, normal paper colored black with a black permanent marker on both sides starts to smoke a bit after 5-10 s of exposure. My skin gets pretty warm, and starts to smell oddly (still didn’t understood if something is happening on my skin or it is a chemical released by the LED). At 1 cm (0.4 in), my skin gets so hot that I can no longer keep it continuously at that distance from the LED (and anyway, you shouldn’t do that. I have approx. 2.5-3 W/cm2 of UV at that distance, which is up to 500 times more than UV in sunlight (given a solar irradiance of 1120 W/m2, and assuming 5% of it is UV radiation, from Wikipedia). At this distance paper starts to darken because of the temperature it reaches. At 5 mm (0.2 in), paper starts to burn. The blue dot of fluorescence on paper is too bright to look at. Sometimes paper can ignite (I never got it to light on fire, but it became orange, so combustion was initiated). The calculated irradiance, given 4 W of optical output in a 8 mm wide circle (measured with fluorescence on paper), is 8 W/cm2, about 1400 times more than under sunlight. Anywhere closer, and paper, wood, black tape, and any material which is not very transparent to UV or doesn’t reflect a lot of it, will heat up and burn. All distances measured from the lens. Since the LED is a good approximation of a point source of light, given its intensity (a lot of power from a small surface), it can be collimated into a narrow beam. I also like the fact that the lens directs all the light the LED produces into that 60° beam, which can be further collected by a second lens, giving an almost perfectly collimated beam (that, and that’s important, contains ALL the light the LED produces). If the source is infinitely small, you can (in theory) get a diffraction-limited beam, but in my case, since the LED has a non-zero size (of course), you can focus light up to a certain point. In my case, using a car headlight lens, I got a 5° beam. I got a circular, well-defined spot (an image of the lens covering the LED basically), 40 cm in diameter (16 in), 4.6 m (15 ft) away (that’s how I calculated 5°). With the unfiltered LED, I feel heat on the lips 1.5 m (5 ft) away and on my hand 1 m (3 ft) away in the collimated beam. But that’s not all. I discovered (and yes, I specify this, I re-discovered myself) that, using a second lens above the first one (for a total of three lenses, counting also the lens on the LED), I could re-focus almost all the light emitted from the LED in a spot about the same size as the LED, but ~15 cm away from it. (Notice that you can not focus light into a spot smaller than the light source itself, if you do that without wasting a significant amount of light. Or, better, you can not achieve an irradiance greater than the one you started with. This rule is also valid when you play with a magnifying glass under the sun. No matter what you do, you will always have a lower limit for the spot size, for a given amount of power). This way, I can burn things without damaging the LED (if only I knew that before!). You can burn paper, cardboard, wood, transparent polycarbonate (remember, it is a UV LED) and so on. You can apply this focusing technique to every light source. While writing this review (it is a review after all) the lens came off the LED. I don’t know if it was due to the extreme thermal excursions or because the glue isn’t strong enough. I even used sandpaper on the lens, before it came off, to remove some dark spots caused by my burning activities, and it didn’t came off. So now I have the opportunity to show how the de-domed LED looks like. If you are going to use parabolic mirrors instead of lenses to focus this LED, you should remove the lens, and, if you can, install a new one that does the opposite of a normal lens: diverging the light to the sides of the LED, leaving a dark spot in front of it. And now for some images... Beam pattern ~10 cm (4 in) away (with lens). You can see that it isn't a perfect circle, but rather a square-circle with holes on the corners. I still like it. Brighter image Then I marked 8 points on the paper with a yellow highlighter, to then calculate the beam angle: Results: 70.5° (left-right, up-down in the image above) and 73.5° (diagonals). So not really 60° as advertised, but still quite close. I put the vertex of the (imaginary) triangle on top of the LED lens. Circular spot of the 5° collimated beam: LED with lens (don't mind the glue residues on it, it came clean of course): LED without lens. One of the chips is slightly darker, but that was my fault. If something deposits on it, it will simply burn: Lens alone: Using a USB camera with a screwable lens (I can unscrew it completely) I made a sort of DIY microscope, and took some images of the LED chip, turned on at a very low current. Here you can see that the LED chips aren't perfectly matched. Also there is quite a bit of space in between, but I guess it isn't easy to put them very close to each other. Even more magnified image: Very rough drawing of the lenses setup to re-concentrate light away from the LED: Setup in real life: Some burn tests (away from the LED, with the above setup): Burns on wood, putting it a few millimeters from the LED (with lens). The big blob is just black spray paint: Burn on the same wood (red circle), done far from the LED this time: Burns on the same piece of wood, close to the LED (with lens), at the (approximate) written distance: Images of the four chips burned on paper with lenses (far from the LED). LED without lens ("de-domed"): Polycarbonate goggles, burned far from the LED in a couple of minutes. They were broken, so this is not a waste: Now I reached the maximum upload size... I will add other details soon. Hope I didn't make any mistakes.

Girls & Boys.....The Future Has Arrived. Here is a #1 of what I hope will be a new approach to UV LED Lighting. This #1 has four different wavelength LEDs on each 20mm star, they are 365, 375, 385 & 395nm & the output is 10 Watts. I have assembled nine of these LEDs to produce nearly 90watts of mixed UVA. This is all in development at the moment. Enjoy the dream....

Hi, This time I went down a bit with the wavelength, and tested a 340 nm LED, found on ebay. The seller claims are: 3 W power (in) 60-70 mW power (out) 340-345 nm wavelength The LED is rated at 500 mA, and the forward voltage (from the seller) is 4.6-5 V. The viewing angle is quite wide, at maybe 150° (I didn't measure it yet). That's how it was delivered: Paper container (with bubble wrap inside), with a "ball" of bubble wrap inside Inside the "ball" there was what looked like an anti-static bag and some kind of protective material (like a spongy styrofoam). The LED was inside the bag of course. The LED came with two blobs of solder (I will not solder wires in those places anyway) So... this LED created a lot of questions. That's what I expected: Green color when white-balanced with a typical UV sunlight white-balance; Dark glass (not black, but noticeably darker); Weak output (that's normal for this kind of LED, they are inefficient below 365 nm). As you will see, the reality turned out to be (mostly) different. About the color... this is the color of a 365 nm LED torch, with white-balance; (243, 255, 7) It is a greenish-yellow, no surprise here. ...And that's the LED, seen through a 3 mm thick ZWB1 filter: (255, 255, 6) That's almost a pure yellow. I think that it shouldn't be like that, maybe something is wrong with my camera. Comparison: Regarding color... I had a curiosity to satisfy: how does the human eye see light at this wavelength? It happend (mostly accidentally) that I saw a 365 nm LED, with no protection. It appeared violet, especially at low power. So, I thought that 340 nm would have appeared violet too. And... I did it. Running the LED at low power (~1 mW output), and filtering it with the same 3 mm thick ZWB1 filter I used before (the LED emits a bit of white light), I briefly looked at it. I noticed two things: My eyes have a huge focus shift down there (that was expected); And... the LED appeared BLUE! Not violet, but a rather nice shade of blue, a bit on the violet side. L cones (red) lose almost all sensitivity in the shortest wavelengths, and the only cones still sensitive enough are the "S" (blue) type. I will not do that again, and I will always use eye protection when working with this LED. That's the approximate color I saw (50, 0, 255) So, light appears violet only in a well-defined range, maybe ~350-430 nm. If you want to see the same color I saw, but MUCH more safely, look at a 435-440 nm LED or at the 435.8 nm mercury G-line. Running the LED at the maximum rated current of 500 mA required 4.2 V, for a total power consumption of 2.1 W. LEDs emitting at short wavelengths require high voltages (see here https://www.ultravio...ng/page__st__20). At 340 nm, photons have an energy of ~3.6 eV, compared to 3.4 eV at 365 nm. Another surprise came with imaging. The LED is quite weak, but it can easily light up paper, highlighters, and all sort of fluorescent objects. The colors seem the same of those under 365 nm light. I needed f/2.8, ISO 80 and 60 s of exposure to capture correctly exposed images, with the LED ~20 cm away from the subject. I initially used my ZWB2 (2 mm) + chinese BG39 (2 mm) stack, which worked well, but then I switched to the ZWB1 filter above (used alone). Unless otherwise specified, the settings are f/2.8, ISO 80 and 60 s exposure for all images. They aren't white-balanced. Not really the best way to run the LED, but it works and it dissipates heat well. I then made contacts with the alligator clips by holding them with my hand. I will eventually mount it properly to the heatsink. I noticed two things: Typical glass does NOT darken, it is still very transparent; Apparently, glass fluoresces emitting UV light (UVIUVF). You can see it glowing in my photos.; Glass piece My hand Glass jar (340 nm) (365 nm), with a torch ~1.5 m away Same, but only 15 s of exposure Last, this is the link if you want to try it (again, I have no affiliation with the seller): https://www.ebay.com...60eff6adc8ac2df. I also noticed that my LED, this one https://www.ebay.com...Ks2aloJPxecaFYg, and this one from Thorlabs https://www.thorlabs...tgroup_id=6071# all seem to be the same exact one, more precisely this one https://www.aptechno..._AAP63_60mW.pdf That's all for now, maybe I will post other experiments in the future.

I will below discuss the properties of LEDs and how to setup a power supply driving them. Current.LEDs are diodes and the main limiting factor when driving them correctly is the current. Too much current will break them. All semiconductor diodes, including LEDs need to reach a voltage before they conduct any current. When that forward voltage is reached the current will increase rapidly. Too much voltage applied to a LED will cause an over-current destroying the LED. Driving power LEDs close to the maximum current avoiding a breakdown is best done with a controlled constant current. The forward voltage is dependant of the type of semiconductor material used and that depends of the wavelength the LED is designed for. The forward voltage also varies with the temperature. Cooling. The second very important limiting factor, especially for power LEDs is their chip temperature. If proper means for cooling is lacking they will quickly overheat and break. As the LEDs active chip is rather small even a relatively low power can rise the internal temperature of the chip quickly. To avoid that a power LED should be thermally well connected to the environment for cooling. A good example is the driving module including the LED in the Convoy S2 UV flashlight. The module is a massive metall unit that screws directly into the flashlight's body. I estimate that that solution safely can dissipate as much as 1-2W. High power LED arrays in industrial UV-curing units are often water-cooled just like processors in extreme gamer computers. Then they can handle power losses of several hundred Watt. The heat that has to be cooled away is the supplied power minus the emitted power in the light. The efficiency converting electrical power to optical power is normally lower than 50%. Polarity. Another important thing to observe is the polarity of the voltage supplied to the LED. LEDs are quite sensitive and will be destroyed by reverse polarisation, with even modest voltages. Many types of LEDs can only tolerate blocking up to five volts, when reverse biased. The positive voltage must be connected to the LED's anode and the negative voltage to the cathode. This is especially important when dealing with LED-arrays where several LEDs normally are connected in series. Then the voltage needed to drive the series coupled chain of LEDs is the sum of all forward voltages. Multiple LEDs. If several LEDs are to be connected together, the safest and most efficient way is to connect them in series. Then the same current will pass through them all. If LEDs for some reason must be coupled in parallell, each of them must have a series resistor to balance out the individual differences of the forward voltage-characteristics always present. Such balancing serial resistors waste energy and adds unnecessary heat to the design. Power sources, their setups and connections.Methods setting up a power supply for LEDs depends of the type of power supply and it's capabilities. A summary: Start from low or zero settings of voltage and current. Adjust the current limit upwards to desired current, to below the maximum rated current of the LED. Then carefully increase the output voltage until the current limit is reached. activating the CC. Then increase the voltage settings little it further to allow for temperature related changes of the LED's forward voltage. An advanced variable Lab-supply can often have the parameters set before activating the output. Those supplies always have some kind of indication of set and/or active voltage and current. The current limiter is just set at some level below the rated maximum current of the LED. I normally also start with the voltage setting to zero or below the expected forward voltage before activating the output. After activating the output, I carefully increase the voltage until the current limit (CC) kicks in while observing the voltage changing. There is a rather small voltage range where the current increases from almost nothing up to the set CC-limit. A power supply-module intended to be setup to the proper operating point for driving LEDs in a fixed setup can be a bit more challenging to set up. They often have small multi turn potentiometers without any indication of rotation direction for increasing or decreasing the parameters. The potentiometers are often marked CV and CC on the PCB. (Constant Voltage and Constant Current) If that information is lacking you first have to experiment a bit, preferably without the LED connected. You will need a multimeter for this setup. These modules sometimes cannot handle a CC-situation into a direct short circuit of the output. They need some load to create some voltage over the input.

This is a very good and relatively understandable summary of the IEC 62471 Eye safety standard: https://smartvisionlights.com/wp-content/uploads/pdf/IEC_62471_summary.pdf It explains several important aspects for eye safety and what type damages the standard intends to protect us from. Interesting parts also include Risk levels Exposure times Types of labeling needed for products in different risk levels.

I inherited an old "OSAWA 52mm PL ∆" polarizer along with a bunch of other equipment from my sister when she moved to Colorado, and I just tested it in UV. There is a noticeable change in the sky. Prior work on this topic has been done by Jonathan here. Camera: Sony A7S modified for full spectrum Lens: AF-Nikkor 80mm/2.8 Filters: 1.75mm S8612 + 2mm UG11 Settings: F/2.8 ISO1600 1/8" (aperture wide open), White balance: in camera, off PTFE without the polarizer on No adjustments to the images besides resizing and lowering the exposure setting by one stop. All three images have the same settings, as verified by copy and pasting them in PhotoNinja. No polarizer, exposure reduced in PhotoNinja by 1 stop to make the sky visible With polarizer, rotated to give the darkest image With polarizer, rotated to give the lightest image ---- I also tested (with same settings and processing as above) a Tiffen polarizer: Rotated to give the darkest image: Rotated to give the lightest image: ---- Putting all the results together, it seems they perform pretty similarly.

Does anyone have any experience with using light modifiers for UVIVF photography? I've been thinking about ways to soften the light sources and it seems like most traditional modifiers (softboxes, diffusers, etc.) would be impossible to use due to their fluorescence under UV. The only thing I could think of that could have a chance at working would be something like a bounce. Looking forward to hearing people's thoughts on the topic.

Here I will talk about the differences between "normal", classic UV (<400 nm), and slightly deeper UV (<380-390 nm). My experience about this is the following: -With nornal UV, you have more colors and more sensitivity. -With deeper UV, you lose colors and sensitivity, but your images will be "more UV" than the normal UV ones (darker polycarbonate, darker sunscreen, etc.). The filter I have used to cut the upper portion of UV is a 3 mm thick ZWB1. For every image I used a full spectrum Panasonic DMC-F3. This is how 3 objects appear with a "light" filter (ZWB2 2 mm + chinese BG 39 2 mm). The ZWB1 in the first image appears yellow because it blocks longer waves and passes shorter ones. In the last image, polycarbonate appears blue for the opposite reason. With the "light" filter, I have enough sensitivity to shoot in the shade, on a sunny day. The 3 mm thick ZWB1 filter, with some glue on the sides because I attached it with tape. ZWB2x2 + Chinese BG39x2 f-stop: f/2.8, ISO 1600, 1/40 s exposure. Plastic lens. ZWB2x2 + Chinese BG39x2 f-stop: f/2.8, ISO 1600, 1/50 s exposure. Polycarbonate goggles. ZWB2x2 + Chinese BG39x2 f-stop: f/2.8, ISO 1600, 1/20 s exposure. When I use the "heavy" filter (3 mm ZWB1), the goggles are completely black, even if I can still see the sun through them. Polycarbonate goggles #1. f-stop: f/2.8, ISO 1600, 1/8 s exposure. ZWB2x2 + Chinese BG39x2 Polycarbonate goggles #2. ZWB2x2 + Chinese BG39x2 f-stop: f/2.8, ISO 1600, 1/8 s exposure. Polycarbonate goggles #3. ZWB2x2 + Chinese BG39x2 f-stop: f/2.8, ISO 1600, 1/8 s exposure. You can see that the goggles are slightly transparent. This doesn't occur when I use the ZWB1 (3 mm) filter. Now, unless otherwise specified, all the following images have been taken with a 10 W 365 nm LED. This LED is very powerful, it can burn paper and wood when very close. I should dedicate an entire topic to it. Visible reference, taken with my phone. Everything is transparent in visible light. The thing at the left is a piece from a broken polycarbonate goggle. UV with 10W 365nm UV-LED f-stop: f/2.8, ISO 800, 1/40 s exposure. UV with 10W 365nm UV-LED f-stop: f/2.8, ISO 200, 1/8 s exposure. UV with 10W 365nm UV-LED f-stop: f/2.8, ISO 400, 1/60 s exposure. UV with 10W 365nm UV-LED f-stop: f/2.8, ISO 800, 1/100 s exposure. Now, this is the difference a 3 mm ZWB1 makes. In the first photo, I didn't use it. In the second one, I put it over the LED to remove the upper 385-390 nm region. The difference is pretty visible. You can also notice that I lost more than 2/3 of sensitivity with the filter. UV with 10W 365nm UV-LED f-stop: f/2.8, ISO 200, 1/25 s exposure. UV with 10W 365nm UV-LED + ZWB1x3 f-stop: f/2.8, ISO 200, 1/8 s exposure. As last images, I imaged the polycarbonate goggles and the small plastic lens with a 405 nm LED, using the usual ZWB2 (2 mm) + BG39 (2 mm) stack, and keeping the usual UV WB. Everything appears blue because UV light in that region appears blue when white-balanced. Those should be 390-400 nm images. Completely transparent lens. ZWB2x2 + Chinese BG39x2 with 405nm LED. f-stop: f/2.8, ISO 800, 1/8 s exposure. The spots on the paper below are burns from the UV LED I talked about earlier. Semi-transparent polycarbonate goggles. ZWB2x2 + Chinese BG39x2 with 405nm LED. Same settings. I have other images, but I don't want to make this post too heavy. I think that this is more than enough for now.

Hello everyone My name is Michelle, was born in Taiwan and immigrated to Texas many years ago. I am a Pentaxian, member of Texas Native plant society and amateur naturalist. I love hiking with my dog. I have a converted Pentax k-01 (full spectrum), Pentax K1ii and a few IR filters from Kolari vision. Pentax k1ii + Jaxman UV flashlight for UVIVF, Pentax k-01 for IR photography. Nice to meet you!