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I have been using UniWB settings since about 2004 for all my digital cameras over the years (Nikon D70, D200, D300, D500, D700, D800, D810 and D850). I have never had a problem building the UniWB reference target from scratch on the computer. A project i am working on requires the use of an unmodified Nikon D40 with a UniWB reference. I cannot get the D40 to capture a pre-WB shot of my target, which is often referred to as "wine" colour, being a reddish purple. No matter what I do, the D40 will not accept the captured image of the "wine" target as a WB. This is a standard procedure that has worked for every other Nikon I have owned for the past 16 years. Has anyone here ever successfully produced a UniWB for the Nikon D40 and if so would you be prepared to provide a copy to me? Thanks

Getting blue/purple flowers to be the correct color has become quite a difficult task. The flower is a Penstemon which has a striking, vivid dark blue color combined with some moderately dark purple/pinkish blushes. I cannot get the correct color unless I adjust the color manually* after conversion and white balance. I recently posted an example of a Blue Flax flower for which I had a similar problem. But this Penstemon flower is worse. It is completely off in color. *By "manual color adjustment" I mean a color adjustment made using either a color brush in PSE or using a color point in NX2 either of which are applied only to the flowers. Here are 3 conversion attempts followed by the repaired color. This Photo Ninja profiled version is only slightly closer to the actual color. This version is close enough to keep. The color was repaired in Capture NX2 by placing a color point onto a flower and adjusting the red (less) and blue (more) sliders until the color looked as much like the flower before me as I could make it. I also had to darken the color with the color point brightness slider. I'm sure everyone said whatever there is to say about this when I showed the Blue Flax flower, so I'm not really expecting any replies or comments. However, this example may be of use to someone in the future who needs to know that the correct colors can be "painted in" successfully. :bee:

Hello all, I'm a new member and have been trying my hand at UV photos. I wanted to post some of my early attempts and ask some very intro-level questions to help me get off the ground. Forgive me for a general "getting started" post rather than specific posts for each question. All UV shots are with a Fujifilm X-t3 full spectrum conversion and a Kolarivision UV pass filter on the Fujifilm 27mm f/2.8 pancake or Fujifilm 60mm 2.4 lens. 1. I'm clueless about white balance for UV. I've read online that one should use a gray card and I've read the advice on the present site as well. Seems clear that the typical method I've used for IR photos (i.e., brightly lit green foliate for a custom WB) does not work too well. Auto WB also doesn't seem to work. First shot below is auto WB. Second shot is custom WB on green foliage. Third shot is a BW version. Ultimately, I think I will do mostly B&W UV, just as I have done lots of B&W IR (see fourth shot, just for fun). I think from these shots I can conclude that the 27mm f2/8 Fuji pancake does ok with UV. This is the "correct" pattern for a dandelion, right? This would indicate little or no IR leak on the Kolarivision filter I think. 2. In full sun, f/2.8, ISO 160, does the 1.1 second exposure seem ok? From that would you say this lens is passing acceptable amounts of UV light, or would you say that this is too long of a shutter speed indicating that the amount of UV light being passed is problematically low? Of course I could raise the ISO (although, since the X-t3 is a crop camera, I would not want to go too high). I mostly do nature photography which typically means wind, so usually 1 second exposures are not fun. 3. I have several old Nikon AI-S lenses (55mm 3.5 macro; 28mm 3.5; 105mm 2.5; I also have the 50mm 1.8D). All 52mm filter threads. The only UV pass filter I have is the 39mm from Kolari (purchased because Kolari said that the 60mm 2.4 macro lens from Fuji is good for UV (and has a 39mm thread); I'm also using it on the 27mm f2/8 which also has a 39mm thread). I can still exchange the 39mm Kolari UV pass filter for a 52mm version, but would probably only do so if some of the AI-S (or the D) lenses work well for UV. I've seen lots of things that older, simpler lenses with less advanced coatings might work well with UV, but I haven't seen specific recommendations for these AI-S lenses. Any thoughts? 4. Kolarivision's website noted that the Fujifilm 60mm macro lens was good for UV, but I found it to be hotspotty--even wide open as the last picture shows (wide open it is more like vignetting, but stopped down the lighter center becomes more pronounced and well defined). Stopping down to 5.6 or 8 made it significantly worse. I am well versed in the hot spot issues with IR, do we usually have the same problems with UV? (and yes, that is the ghost of a man visiting a grave just to the right of center in the background). But....IT'S HIS OWN GRAVE!!! ;-) Thanks everyone for any newbie advice you can offer. John

I was working up the photo of the abaxial side of this Desert Marigold to possibly add to the topic. The white balance result was *very* interesting. Gear: Nikon D610/fullSpec + UV-Nikkor 105/4.5 + BaaderU UV-pass Filter + SB14 UV-flash Mod Here is the back side of the Desert Marigold as converted in Photo Ninja and with all the usual editing except for white balance. Click up to get 1200 pixel width. The flower was photographed against a Spectralon square which makes WB easy. I simply dragged the PN white balance dropper around some of the Spectralon area. (Yes, there is grunge on the Spectralon. Kindly ignore.) But what an unusual WB result !! I sampled the colors and found pinkish-browns and light cyans. These colors are not "supposed" to occur in a properly white-balanced UV photo. Yet here they are. This is an unresized crop. Here's a screen shot blow up to make it easier to see the weird colors. Is this result because of color noise? In ample light the D610 is just too good at ISO-200 to produce much color noise. So I am thinking that these unusual pinks/cyans have something to do with the flower ray (petal) structure? Flower rays and petals can transmit light as well as reflect light. Transmitted light hits internal structures or interacts with surface cells and the result is iridescence or other odd effects. Is there some moiré here? Maybe this is some kind of demosaicing artifact? Moiré, maybe? But this photo was under a BaaderU. How do false pinkish-brown and false light cyan fit into the usual blue/yellow/gray/black/white palette which we see after white balancing? Maybe this is color noise. But shouldn't color noise under a BaaderU be not-pink and not-cyan? What do you think?? I converted the photo in old Capture NX2 and got the following result. It looks rather different but still has some odd colours. Interestingly, NX2 had trouble white balancing this. It left some cyan highlights on the Spectralon. That was strange. This is a blowup of an unresized crop so that the colors will be more easily seen. I think that NX2 does not apply as much saturation as does Photo Ninja.

I thought it would be interesting to compare the different CCWB (Camera Custom White Balance) effects based upon the targets used when setting the CCWB. I used a Panasonic full-spectrum GF1 which permits two custom WB. Lens was Schneider Kreuznach 40mm f/4.5 Jsogon with Exakta mount. UV bandpass filter was an SEU Gen1. All photos taken in ISO 400, f11. Focus used for visible images was also used for UV images. Post processing was a single-click WB in Gimp2, then crop, and reduce to 1000px width. Visible - entire image chosen as WB target http://uvroptics.com/images/VisNWBawb1000px250.jpg crop of above http://uvroptics.com/images/VisNWBawbcrop250.jpg PTFE target held in front of lens as WB target for UV http://uvroptics.com/images/UVPtfeawb1000px254.jpg crop of above http://uvroptics.com/images/UVPtfeawbcrop254.jpg UV entire image chosen as WB target http://uvroptics.com/images/UVNwbawb1000px251.jpg crop of above http://uvroptics.com/images/UVNwbawbcrop251.jpg

Here is my start to processing....... Sunflower, Canon 40mm, SEU3 + S8612 CWB in camera, open in PN.... PN won't let me click WB ? PTFE not blown & Sunflower too dark ?

I was working on Oenothera pallida (Pale Evening Primrose) today and was curious to review the white balance appearance of this false-blue flower both with and without the application of a camera color profile. A visible color profile photo (not shown) was made using a D610 + UV-Nikkor 105/4.5 + Baader UV/IR-Cut filter to photograph a Color Checker card. Three minutes of work in Photo Ninja (tutorial reference 1st link below) then provided a saveable set of accurate visible colors to apply to any visible photos made with this gear. I would say, roughly speaking, that such a camera profile for a converted camera certainly gets you into the visible color-accuracy ball park and very likely well on your way to third base. Those wishing a color-accuracy homer will need to understand and conquer a great deal of additional technical variables. I'm happy stopping at 3rd. However, when rendering a reflected UV photograph, we have no real definition of "color-accurate" for the false colors. I think that this gives us license to either apply or not-apply a visible color profile prior to white balancing the UV photo. In earlier years (see 2nd link) I tried to make the case for why we should use these camera visible profiles in UV photos. These days I am not so insistent. Use or do not use a converted camera vislble profile for UV photos as you please, OK? Reference: Photo Ninja: How to Make a Custom Light Profile See also: Colour Calibration in a Converted Camera The Primrose raw photo used for this demo was converted in Photo Ninja with the usual simple tweaks for black/white points and some detail enhancement. Sometimes I also use the shadow slider, iillumination slider, and/or contrast sliders. I keep the color intensity between 50 - 60 for the Plain setting. White balance was made against a Spectralon background. (It is so fast and easy to convert in PN that I rarely use anything else these days. I only wish for a brush so that I could selectively apply the detail slider settings.) After white balance was made in PN's Color Correction tool, I selected No Profile from the Light Source drop-down. This result is on the left. After saving that, I selected the D610 profile to get the result in the middle. The 3rd result on the right used the generic PN Daylight profile. I always like to sample colours and compare them to their fully saturated versions, so I proceeded to do that for my 3 Primrose renditions. Obviously sampled results will vary depending on where you sample, but we still can get a feel for how the profiles are behaving. The specific Hue/Saturation/Brightness and RGB numbers are from 5x5 samples made at the same place on each rendition. The predominant channel in each rendition is blue. Blue is considered to be 240° on the color wheel. Here we get 225°, 239° and 237°. So the first color sample is about 15°, one quarter of the way closer to Cyan than the other two samples which are almost "pure" blue, although desaturated. So what color should our UV false-blue be? You decide.

Custom White Balance, CWB, what do you do when the camera won't take it & says Failed ! ?

After dabbling mainly with my b/w converted camera, I finally worked up the motivation to go out and do some proper colour-UV photos I've searched around a bit, and since nobody knows how bees actually do perceive the EM-spectrum, I've decided to stick to the accepted nomenclature, and to call these photos bee-vision. First, the basics: Camera: Canon EOS 6D, full-spectrum conversion (almost all taken between ISO 100 and 200), WB set to flash (5400 K, I believe) Lens: Nikon EL-Nikkor 80mm, f/5.6 (mostly af f/8), handheld Light: Overcast day, so used a Yongnuo YN-24 EX-TTL macro-flash, where I've replaced the cover with a plastic from a CD-box. Filter: ZWB3 + S8612 (This makes me appreciate by b/w-camera even more, because with a lot of concentration it's possible with this filter-combination to look through the viewfinder and find focus, at the end of the session I only needed 2-3 tries per flower; whereas with teh b/w there is just the S8612 required which makes focussing and composition much easier) Post: WB set arbitrarily to some values where I liked the result (not the same for all photos). Cropping, of course, and a bit of correction to highs and lows, that's about it. Then, the usual admissions: I did try to identify the plants from the plates which are stuck into the ground, but chances are that I got some of them wrong. The VIS-shots werer taken with my mobile phone, and not always from the exact same angle. [Edit]Thanks to Birna for the help. 2 out of 10, that's a new low, even for me [/Edit] 1. Primula Althaea officinalis, Eibisch: 2. Anemone blanda Aster dumosus "Kassel", Kissenaster: 3. Helleborus argutifolius, Korsische Schneerose (reminds me of Audrey II from https://www.imdb.com/title/tt0091419/ ): 4. Pulsatilla halleri slavica, Küchenschelle: 5. Anemone ranunculoides Saxifraga umbrosa, Prozellanblümchen: 6. Ranunculaceae Silene uniflora, ssp.glareosa; 7. Ranunculus ficaria Unknown: 8. Corydalis Unknown: 9. Euphorbia Unknown: 10. Primula Unknown:

I have a lot of dandelions growing in my garden. Today they are not fully open because of the overcast weather, but the pattern still shows up. This is just a quick photo I took, this topic is intended to be informal. Do I need to post the settings?

I searched through the forums for this, as well as searching for the URL at which the product is located, so seems like no one has shared this before. I figured I'd bring it to everyone's attention. It only has RGB and GBW squares, and costs a whopping $875 (US dollars) though. http://www.imagescienceassociates.com/mm5/merchant.mvc?Screen=PROD&Store_Code=ISA001&Product_Code=TUVUVGC&Category_Code=TARGETS

Spectralon fluorescence? Well, You be the judge. The one thing I might add is that after I shot these shots, I re-sanded the Spectralon (according to their directions) to make sure I had a clean pristine surface. The sanding cleaned it up, yes, but the surface still fluoresced the same 'gray?' surface, same intensity, no difference other than the dust and smudges were gone. Three shots of the Spectralon, (left) Visual, camera has Zeiss T* + S8612 1.75mm on the lens. (center/left) UVIVF #1, Spectralon and Straight-on torch shot, using Convoy S2+ 365nm Nichia with U-340 2mm filter on it, and the camera only has Zeiss T* on it. Both Spectralon and Torch shots have the same settings. (right)UVIFF #2, Spectralon and Straight-on torch shot, using Convoy S2+ 365nm Nichia with U-340 2mm filter on it, and the camera only has Zeiss T* + S8612 1.75mm (3.5mm) on it. Both Spectralon and Torch shots have the same settings. Settings are noted on test photos. Direct head-on shot of U-340 2mm filtered Convoy/Nichia 365nm UV torch These correspond directly to the photos below each torch shot. Dark room. Some background fluorescence reflected off the left hand black torch glass filter front. The first two shot/setting to the left correspond to the two left hand torch shots and setting above. You decide. I don't want to think Spectralon fluoresces, so show me I am wrong.

I had a quick thought that I think might be interesting. I searched on the forum, but I didn't find something similar. I remember when I asked someone to white balance a test image I created to see the result (here). When I did this I wanted to prove something else (read that topic), but now, having the possibility to white balance my images myself (using IrfanView), I wondered if there was a difference. I already had some doubts about how well can IrfanView white balance, and I noticed the odd results I obtained several times. In particular, I had "different-than-normal" results here. My test image (made in Paint, nothing special) consisted of three squares with three colors I think are commonly see in RAW UV images, or UV images that are not white balanced. They are, from left to right, bluish magenta (basically purple) (128, 0, 255), magenta (255, 0, 255) and reddish magenta (255, 0, 128). I asked someone to white balance it in the middle square, and Birna did it. She obtained colors I would expect in a UV or IR image (more IR than UV): Measuring the colors in Paint, I have, from left to right: (121, 155, 252), (249, 248, 246(?)) and (250, 232, 108). She did the white balance in Photo Ninja, but had to convert the image to .jpg in Photoshop, and said that could have altered the colors just a bit. Below is an old IR image I made with my 730 nm and 850 nm LEDs, white balanced in-camera: The colors are kind of the same. But here is the interesting point: what happens if you take the same initial image, and white balance it in IrfanView? You get this: Way different. The colors are (42, 170, 169), (170, 170, 170) and (170, 171, 43). I don't think most of us would like UV images with those colors, even though they could look interesting. My question is: can you (all) white balance my initial image with other programs you have, post the result and write the RGB coordinates you got? This could be useful to see how well the most common softwares white balance images.

So I was wondering the following. If you had a known red fluorescent object, known green fluor thing and known blue fluor doodad, can you then make from them a proper white balance in a UV-induced Visible fluorescence photo? This would be analogous to using the red, green and blue patches on a Color Checker card to make a proper white balance. (Actually, I don't know if this can be done either.)

Once again I am attempting UVIVF on a gourd. Long-time followers of this forum will remember my cursed (but gorgeous) first attempt. This time I have taken a great deal more care with the color processing. Whether it was worth it, I leave up to you all to decide. The new procedure was as follows. Equipment Nemo torch with fluorescent ring placed behind the filter to prevent contamination. Filter is the stock filter that came with it. Color Checker Passport 2019 Micro-Nikkor 55mm/2.8 lens Sony A7S camera (converted) Aluminum foil Foldio light box for diffuse lighting Stack BG38 2mm + Tiffen Haze 2E Process I placed the Color Checker inside the Foldio box with the built-in white LED lights on and took a photo of it. I followed Andrea's directions for producing a Custom Light Profile in PhotoNinja, using white balance off the white square in the Color Checker. The resulting image of the Color Checker after the Custom Profile was applied looked like this: I then placed the gourd on a piece of aluminum foil (dull side up) and shot a lot of photos of it under the same lighting as I used above with the Color Checker but with focus varied in small increments. (This was done using the Sony Imaging Edge software to take photos directly into the computer as I changed the focus.) I used Photoshop CS6 to make a focal stack and produced the following image. The image has been adjusted for contrast and to white out the aluminum foil: I then removed the Foldio box (which fluoresces brightly) and placed the gourd back on the foil and turned out the lights. I shined the Nemo torch on it using several 1" ISO100 F/8 exposures to make another focal stack. The image below was the result, with some further adjustments in Photoshop to remove lint in the background, and also to tweak contrast. I didn't change the colors this time, having gone to so much trouble to get them. I fully realize that using the white balance of the Foldio lights for this is just as arbitrary as ANY OTHER CHOICE of UVIVF white balance (with the possible exception of those expensive UVIVF white balance standards that Andrea has).

As many here know, the SIgma Foveon sensor makes it possible to get a Full spectrum look which is reminiscent of the old Aerochome films. Two methods have been promoted and explored already: 1. "Rich" Full spectrum: Remove the Hot mirror, get a custom white balance on grey/white card, almost no post-processing is needed. This will get you a wide variety of red/yellow and magenta hues in the vegetation and blue skies. 2. With additional green filter, for example Hoya X1 Green: Remove hot mirror, choose light bulb as WB preset, install the filter and shoot. This will get you magenta tones and more accentuated, cyanish skies. I always had my problems with both these methods: 1. The "Rich Full spectrum" method just lacks the magic and mood of old Aerochrome. It's hard to pinpoint to a specific trait. For me, it lacks the stark contrasts, the dark skies and the surreal lighting of scenery. It just looks too natural/normal for my taste. 2. The Green filter method gives you more of that Aerochrome charm, but it has greenish/cyanish skies, and the magenta tones are quite uniform and too pinkish for my taste. So yesterday, I spent an afternoon in my atelier and just tried out different filters with my SD1, in the hopes of achieving other ways to a more authentic Aerochrome-style emulation. I was trying to get good custom white balance, which is soo difficult with Sigma cameras. I tried a classic Red Filter from Tiffen, the 25... Custom white balance whitout filter on, because I just couldn't get a CWB with the filter on the camera. I got a very yellowish image with red trees in it. I thought that this would never work out in post-processing. But I was wrong. So here's what I did in SPP and the final result with additional WB optimization in Photoshop Raw Converter: I also tried a combination of filters: Red and Green (Hoya X1). Unfortunately the lighting conditions were very poor. But in post, I also came up with a very good solution. So now I will try to test both methods in clear sunlight, hoping to see if these methods produce more "Aerochrome" like dark skies and colorations. Recommendations, Comments are very welcome..

Improvised test image with Sony A7 II multispectral, Soligor 35 mm f/3.5 (Kuri clone), rear-mounted Sigma Y52 filter. This filter is from a set of 4 filters in 30.5 mm mounts that used to accompany the Sigma 500 and 600 mm catadioptric lenses. This appears to be a more-or-less standard yellow filter. Manually adjusted WB, but no channel swapping or other processing.

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.

As you may know, I just finished high school. In our classroom, we had the statue of a horse that we called "Rodolfa". She was found on the roof of our school, in the first year, since we were working on a project to imagine how to change the school. I have no idea how and why she went there. Initially she, or it, as you prefer, was completely white. Then a classmate took her home, and his brother painted her "rainbowy". After a bit of time, he brough her in our classroom again, and we kept her for five years. Everytime we changed our classroom, we also took her to the new one. Just after my exam, I had the opportunity to take her. And so, now, she is in my bedroom. I photographed her in UV, visible and IR light. Note: I am sorry if the photos are not perfect, but it's the fifth attempt and I'm done with it. The first time the camera moved; The second time I had a light leak in my UV image; The third time the sun went in and out, since it was a bit cloudy; The fourth time the camera didn't properly focus; And the fifth time the images were good enough. I have a limited hardware, I had to tape my tripod to the ground, white balance each shot in camera with a paper tissue, change the ISO and exposure for the UV image, use a pair of polycarbonate goggles to cut UV in the visible image (UV is a bit visible, it makes the sky pinkish), all with handmade filters using paper rolls and tape, and I have to rely on the autofocus, since I can't manually focus. So... Camera: Full spectrum Panasonic DMC-F3. UV: ZWB2 (2 mm) + chinese BG39 (2 mm) VIS: chinese BG39 (2 mm) + polycarbonate goggles IR: Hoya R72 UV: F-stop: f/2.8, ISO 400, 1/8 s exposure. VIS: F-stop: f/7.1, ISO 200, 1/800 s exposure. IR: F-stop: f/7.1, ISO 200, 1/1000 s exposure. UV: F-stop: f/2.8, ISO 400, 1/8 s exposure. VIS: F-stop: f/7.1, ISO 200, 1/800 s exposure. IR: F-stop: f/7.1, ISO 200, 1/800 s exposure. UV: F-stop: f/2.8, ISO 400, 1/8 s exposure. VIS: F-stop: f/7.1, ISO 200, 1/1000 s exposure. IR: F-stop: f/7.1, ISO 200, 1/1000 s exposure. UV: F-stop: f/2.8, ISO 400, 1/8 s exposure. VIS: F-stop: f/7.1, ISO 200, 1/800 s exposure. IR: F-stop: f/7.1, ISO 200, 1/1000 s exposure. Note: the leg was already broken.

Hi, I bought a Hoya R72 filter (49 mm). Finally I can shoot infrared properly. Camera: Full spectrum Panasonic DMC-F3. F-stop: f/2.8, ISO 80, 1/125 s exposure. F-stop: f/2.8, ISO 80, 1/50 s exposure. Did I underexpose? I feel like they are a bit dark. Today was a rainy day, I hope the next ones will be sunny.

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).

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

Reading through various online photography articles, I often hear that ND filters are "sunglasses for the camera". Thing is, not all sunglasses are created equal. Variations in coatings means that, unlike true ND filters, sunglasses often create a colour cast, so I was curious to see how this would affect a full spectrum camera (given how sunglasses are generally transparent to IR light, depending on how deep you go into the IR). How would the sensor render through a green-tinted sunglass lens vs a brown-tinted one vs a neutral one? So, I bought a bunch of el-cheapo sunglasses with circular frames and 54mm diameter lenses, and a bunch of 55mm UV filters in order to mount them in (to avoid light spills from unfiltered visible light and to avoid vignetting). Unfortunately, I ran out of UV filter rings due to my previous experiments with the dichroic glass filters, and then the coronavirus hit China. Fast-forward 3 months later, and my consignment of filters finally arrived. This weekend finally brought the sunny weather I was needing (with enough clouds to make things interesting) however we've been instructed to stay at home as much as possible, so the only shots I could take were from my balcony. That said, it did give enough variation in reflective materials (buildings, road, evergreen trees, grass and cars). In total, I shot various combinations of reflective blue sunglasses (subtle brownish cast) and reflective orange sunglasses (subtle greenish cast) and/or black sunglasses (somewhat neutral in cast): Additionally, I tried combinations of sunglasses in front of the camera with no other filter, with a hot mirror filter, with a KV 365nm filter (to check for UV blocking ability) for a total of about 2 dozen shots. Custom white balance was done against a piece of white paper after each change of filter. I won't post every single combination, as I'll most likely run out of quota space, but I'll post the more interesting ones. These are all shot with my full spectrum Sony A7 with 28-70mm kit lens, and are all SOOC jpegs (raw converted to jpeg in Sony Imaging Edge 'Edit' application). Only change is to reduce the image to 10% of the original size of 6000x4000px, and to compress it to save space). No other editing done. First up is a visible shot, for reference purposes only: Single strength blue sunglass filter: Double strength blue sunglass filter (held in place with finger-tip). Reminds me a bit of 590nm: Single strength orange sunglass filter, pink foliage: Double strength orange sunglass filter, foliage is more mauve, more definition in the clouds: I stacked an orange and blue sunglass filter, which ended up looking a lot like the double-stacked blue sunglass image with a slightly different hue to the sky. For the black/neutral sunglass filter, I went straight to double strength: Was interested to see what would happen if I stacked one of the sunglass filters with a B+W 403. Here's the unstacked image: Here's the B+W 403 stacked with the orange sunglass filter. Basically turned the image monochrome, allowing just a hint of blue through: And, finally, because this is UV Photograpy, here's a stack of the KV 365nm filter and the orange sunglass filter. A 30 second exposure (sorry, forgot to lock the focus!): My personal favourite out of the lot was probably the double strength orange sunglass filter, for the mauve foliage and somewhat aqua sky colours it rendered. I suspect, though, that it'll be a harsh filter for photographing people. More to come on that another day, when stay-at-home is no longer required!

I have some problems with the colors in my UV photos. I always WB in camera with a paper tissue. If I take a lot of photos in "multishot" mode (you keep the button pressed and the camera keeps shooting), the first one usually has less vibrant colors than the others. In videos I usually get stronger colors than in photos. Here https://www.ultravio...-nectar-guides/ You can see an example. For every image, the filter was ZWB2 (2 mm) + chinese BG39 (2 mm). "vivid" color in camera settings. F-stop: f/2.8, ISO 400, 1/8 s exposure. Same settings. Same settings. Taken the day before. The first photo from this row was almost B&W. F-stop: f/2.8, ISO 1600, 1/8 s exposure. Same settings. ù F-stop: f/2.8, ISO 400, 1/8 s exposure. Same settings. Sometimes, the WB changes a bit, suddently (I increased the ISO, so the sky probably "blew out" and under a typical UV white balance white becomes yellow), but even dark objects became more yellow. In these images you can also see another problem: I have fringing at the sides. Maybe my UV filter is too thick (4 mm). F-stop: f/2.8, ISO 400, 1/13 s exposure. F-stop: f/2.8, ISO 800, 1/8 s exposure. And now, these two images show that, sometimes, I can get stronger colors. F-stop: f/2.8, ISO 800, 1/8 s exposure. Same settings.

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.