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Grabbed some pistachios after work and decided to try UVIIF. I was kind of tired and things didn't go as well as expected. First mistake was using stock Pentax 645z. Hey, it works great for UVIVF, so why not here? Because it takes a very long exposure to force enough IR thru the stock sensor filter. Will use full spectrum camera next time. There are other questions. 1. Using Nemo torch or Adaptalux UV arms Is it enough to use a 25 red or Hoya 72 filter on the camera lens? Or is the Tiffen Haze 2E also needed to block UV? 2. Does my custom IR landscape white balance work here? This isn't vital since I shoot Raw, but nice to get in the ballpark. Thanks, Doug A

Yesterday I spent the evening taking pictures of my funky fluorescent glass collection so that I could discuss with some hobbyists online what sort of glass they are and who made them. I figured that it technically fits in this forum since it's UVIVF so I thought I should post the images. I actually took them with my Sony DSC-F828 initially, I think the retro color rendering is fun, then I had to bring out the Canon 77D because it can actually represent the colors accurately and objectively. I illuminated them with a ZWB2 filtered 365nm LED (which apparently you shouldn't do either since 395nm is the standard in the fluorescent glass community). The green ones are most likely uranium, the more yellow ones are so called vaseline glass, which is also uranium but different shade. The pink/amber/yellow ones are probably selenium and cadmium glass, or some combination of the two. Bonus image, as I said, I later took more images with a 77D, also used a 395nm light this time. I took one of the raw files, color balanced it and then enhanced the colors to highlight the differences between individual shades.

During the winter solstice, there is no sun and UV, and few flowers. I decided to test various types of media useful for white balancing in the studio, with the few flowers in my garden and the lights at my disposal. Flash light (Elinchrom 1000W clear quartz tube) Cold neon fluorescent 6500°K Nemo 365 nm WOOD neon fluorescent Sony A7 fs + Meritar 50 f2.9 Capture One software + photoshop test image with artificial light ~ 3000°K with QB39 filter with 1,5 mm thickness, similar to BG39. TSN 575 + ZWB2 stack (2mm thickness) is similar to BG39 + UG1 (U-360). QB29 is similar to BG25. If you want to check with other software, I can provide you with the 9 Raws with Wetransfer, send me an e-mail photoni@tiscali.it Thank you Toni .

the opuntia ficus indica (prickly pear) photographed in the sun it is an altarpiece collected in Naples many years ago. I also have a variety with orange flowers that hasn't bloomed yet. photographed with Sony A7 full spectrum with BG39 (very similar to a standard view), without filters, BG25 and BG39 + 25. the black and white files are Jpeg directly from the camera with 2000 ° K balance the RAW color files have been processed with camera raw (Photoshop CS6) . what do you think of the white balance? . Thanks Toni

Hi there. After using a modified D70 (720nm) for 13 years, I moved to the Z system and finally decided to also get a modified Z camera to join my regular Z9/Z6II pair. I squinted at the Primaluce Z5 for a while (and read the thread about it here), but they wouldn't come down with their price, so I took advantage of the current cashback rebates, got one new and had it modified for full spectrum by Makario. I'm aiming for IR landscape photography but still chose full spectrum to later experiment with other uses. Using an screw-on 720nm filter for now. As it is widely known, the Z5 (and probably all the other Z cameras as well) won't measure custom WB from an infrared image, as it's apparently doing a "sanity check" on the resulting values and concludes there's something wrong with the measurement. Of course, I tried to trick it into accepting something anyway. Among the things I tried: - putting a D70 jpg onto the card to measure from - modifying a Z5 jpg with experimental WB values via exiftool and measuring from that The D70 is not accepted, and it also seems that if the values in the image for PRE are too extreme (like >2), the camera will not reject them for PRE measurement use, but the PRE setting remains unchanged anyway. Even then I managed to get some wild results, but all are resulting in either too green or too red or too purple images. I will of course set the white balance in RAW processing later, but I'd like to see a reasonable preview of the brightness values in the viewfinder. The closest I've got now is setting the value to 2500K and tint all the way to green, then set a monochrome picture profile. I also contacted the Nikon support, which has been very helpful in other occasions including resulting in actual firmware changes for bug fixes, and asked for a way to set white balance off any source image for artistic freedom, infrared imaging, and colored lighting situations. I would encourage anyone "suffering" from the same problem to do this, too. Did anyone have more success or try other ideas to trick a Z camera into better WB preview? Again, I'm aiming for 720nm in daylight currently. Maik

Hi All, I'm considering jumping ship from my Nikon D3200 to a Sony mirrorless. I want to use more of my vintage lenses in IR, UV and Vis, and the 46.5mm FFD is restricting me from using some of them (for example, my ISCO Ultra Star HD 55mm). That's the primary driver for moving to mirrorless. Primary subjects would be landscapes, architecture, macro, and people (in that order) in IR/UV/Vis. It looks like the A7 (in terms of cost vs features vs weather sealing) fits the bill. Not really interested in the A7R at 36 megapixels, since none of my lenses resolve to that (I'm looking to keep my Nikkor DX lenses, apart from the kit lens, and use them with an adapter). I'll probably get it full spectrum converted by Kolari Vision. So, from an IR and UV perspective, does anyone have any input for: The ability to easily set a CWB in both spectrum bands (my D3200 is lousy at it. I read the methods at http://www.ultraviol...um-nikon-dslrs/ but the D3200 does not have CWB "slots" - you can either take a CWB sample, or use a photo, but using a photo usually doesn't have any apparent effect. No further tinkering is permitted within the camera). The quality of IR and UV video - how does it stack up against, say, a Lumix G camera? Is there a real advantage to having a full frame sensor for IR or UV photography? From ISO 800 upwards, my D3200's crop sensor has an (IMO) unacceptable amount of noise. I have read that full frame sensors generate less noise at higher ISOs than crop sensors, but does that also work under the same principle for non-visible light? I'm not totally sold on the A7 at this point - perhaps a Panasonic or Olympus might be a good fit, too. I have a Pentax Q10 that I've been playing around with, but even with a super short FFD of 9mm or so, the small mount flange diameter, and tiny 12MP 5.4x crop sensor, it isn't conducive to being converted. One last question on Kolari Vision: I got my D3200 converted by them about 3 years ago, before they offered the AR coating. This time around, from a UV perspective, is it worth having that done? Thanks, Andy

EDIT: I amended the title from Shoot in Nikon's Red Channel to Shoot in Nikon Red. EDIT: I amended the title from Shoot in Nikon Red to Pushing WB to Shoot in Nikon Red. I'm pretty sure you can perform the following trickery on other digicams, but I haven't tried it just yet on my A7R or GH1 or K5. This is ----->>>>>> How to Shoot a Very Red Photo with a Nikon DSLR Fill a monitor screen with a Cyan Tif against which you will make a white balance preset. Because you are using a Nikon (for me, D500 today) all of which are known to be rather snarky about white balancing against anything non-grey, do not use a high saturation Cyan. I picked a (153, 255, 255) which was 40% saturated and it worked OK. So, make a typical white balance preset against the Cyan screen. Shoot a well-exposed photo of anything. It will be fairly Red looking. Pull the card and read the mltuipliers for the photo you just took. 4.69, 1.00 .91, 0.00 (read with dcraw and rounded to 2 places) See the strong push towards Red because we white balanced against Cyan? (This should not be a surprise, right?) Now we are going to Fine-tune this wb preset and shoot a photo with it. Fine-tune the wb preset by pushing the cursor all the way right to A6, B0 for max Red. (If you don't know what I'm talkng about here, then oh groan you gotta rtfm.) Shoot a well-exposed photo of anything. Really Red result, eh? Pull the card and read the multipliers: 5.15, 1.00, .81, 0.00. Wow, the wb is even Redder! So now what are we going to do? Rinse & repeat. 1. Select and load the photo you just took into the wb preset slot. 2. Keep your Fine-tuning set to A6, B0. 3. Shoot a well-exposed photo of anything. 4. Pull the card and read the multipliers: 5.66, 1.00, .73, 0.00. 5. GOTO 1. I'm at 6.21, 1.00, .64, 0.00 when I stopped to write this up. How far will the Red multiplier go? I don't really know. When I've done this in the past, I think I've given up after about 15 reloads into the wb preset slot. And yes you can use a Yellow screen or a Magenta screen to force a Blue or a Green wb setting. I've never gotten too far with the Blue. It always turns out more cyan-ish. But I'll try again. The Green has worked out well. And the Red too. So far, I've never gotten a pure Green or pure Red. There's a reason for that but I don't know what it is. I used this a modfication of this trickery to set a WB in my modified D600 and D610 to produce an almost Unitary WB (green) because it enables you to better expose an ultraviolet photo in a Nikon. But sometimes it is just fun shooting in Red or Blue or Green. Edit: added "a modification of". Very Red Photo But note that bit of green & yellow in the weather screen, lower right. Wait, are those numbers green? Or do they just look green because I know they are supposed to be green?

Why Is It So ..... That when we take a White Balance on PTFE/Teflon, that is nearly 100% reflective, it is expected that the PTFE/Teflon will be white in the scene ? If I shine a red light on the PTFE/Teflon, then it will be red. If I shine a green light on the PTFE/Teflon, then it will be green. If I shine a blue light on the PTFE/Teflon, then it will be blue. Now of course, If I shine a white light on the PTFE/Teflon, then it will be white. Easy-peasy... But, If I shine a UV light on the PTFE/Teflon, then it should reflect the UV. Which it should be the CFA equivalent of how the dyes respond to the UV ? Yes / No ?

At the moment Tangsinuo is selling AR coated QB21. They seem to have two different batches of this glass. From the transmission spectrum and the green "shine" one of them seems to be multicoated. The other is possibly single coated. The multicoated one transmits a bit more in the blue/UV-A than Schott's BG38 while the single coated one has a spectrum almost identical to it. My full spectrum converted E-M1 seems to give almost perfect white balance in auto white balance with what I guess is the multicoated type (I haven't yet tried the one I think is single coated, as I have it only in a very small size). The main selling point is the protection from oxidation afforded by the coating, but nevertheless it should also help with flare and ghosting. I show here the spectra I measured (without an integrating sphere).

Hello. Today I have decided to test a few different lightsources that emit UV intense enough to take pictures with: -BeamZ 25w UV Blacklight compact fluorescent bulb -Repti Planet UVB 15.0 compact fluorescent bulb -Domáce Slnko UVIR (a potentially dangerous home tanning machine from probably the 70s or 80s, more info here) -full spectrum Speedlite 199A (very similar to sunlight) -Alonefire H42 12 core 365nm LED torch (a UV blacklight with a decently wide peak) I set up the following scene: Here you can see: -a filter case (background) -a PTFE sheet -a uranium liquor glass -a ZWB1 2mm thick filter -a carrot and an apple set on a white ceramic plate And here are the results, left side is color balanced on the PTFE, right side had color balance turned off in Darktable. Rest assured, I followed basic safety, tried to get exposed to the lights as little as possible and wore yellowed protective goggles. The UVIR discharge lamp briefly smelled a little like bleach when turned on but stopped rather soon. I have no idea if that's the smell of ozone and if it emits UVC, but I ventilated the room well afterwards. The UVB light is safe to get exposed to for short periods of time according to reptile forums which I consulted, even then, I only exposed myself to it briefly. I must say the UVIR discharge lamp also looks really scary when turned on, it emits really intense ghostly blue shine, it also takes a while to reach peak output but when it does, it might be the strongest UV source I've ever handled. If it was collimated it might produce shorter exposure times than those available while outside. Overall, when I briefly tried the UVB light yesterday, I was rather disappointed as it didn't look green at all, which I expected, and relative to sunlight it produced a yellow shine that was almost identical to how I remembered the fluorescent blacklight's shine, however, it turns out it produces much more colorful results, perhaps even a bit better than the sun, since the ratio of 365nm to UVB is skewed more towards UVB. The Speedlite 199A which produces a spectrum very similar to sunlight shows way less color. I also plan to sand down the reflector on my table lamp that I screw the bulbs into, as the white paint it is using right now is not very UV reflective besides the 390-400nm region, at least that's my guess due to the fact that it appears very purple in sunlight. Currently I just taped some aluminium foil to it, but that's far from ideal. Next I would like to try the Exo Terra UVB 200 25w, which should be even more powerful, but I'm not sure it can get much better than this.

So, here is an interesting test... I used my S8612/2mm + U360/2mm stack with 4 different lenses on my camera to compare exposure but at the same time I also got very different results with the camera "auto exposure" metering and color (I used a white PTFE Film card to white balance). Here is the results: Voigtlander 58mm f1.4 (at f4): ISO 1000, 1/60s Sony FE 28-60 kit lens (at 28mm f4): ISO 4000, 1/60s Takumar 35mm f4: ISO 2000, 1/60s Canon 50mm f1.8 STM (at f4): ISO 1600, 1/60s So... why the color is so different?

The following raw color panels were part of some other work I was doing. I white-balanced against a 5x5" Spectralon rectangle. And then took a photo of it for a white-balance reference because sometimes the camera does not measure WB quite accurately when using our strange set of dark and colourful filters. Anyway, for my converted Panasonic S1R the raw color of the Spectralon was the same for both the B+W 093 IR-pass filter and a U340 stack. This struck me as being somewhat weird! Here is that color at an 80% brightness and an 80% saturation. Process: The raw color files from Raw Digger were subsequently averaged in PS Elements, sampled and then boosted to the 80% levels (an arbitrary choice). I was also amused by the fact that the raw color of the U340 was at 341° on the color wheel. For reference's sake, here is a boosted raw color panel for the BaaderU which has a peak at 350 nm. That peak is near enough to the UV region which is recorded as violet or blue or blue-violet in our cameras that you can see some blue beginning to creep into the raw color. None of this means anything very significant. Just having fun with raw colors.

UV color is a complex and controversial topic. For example, Andrea will always remind you that UV false color is not strictly related to wavelength, as it depends on many factors (lighting spectrum, lens transmission, filter transmission, sensor response, white balance...), although we always see the same colors in our UV photos: blues, lavenders/purples, yellows, and sometimes green. Red is not a color that we would expect. A different way of thinking at color outside the visible spectrum in general is to make a TriColour/trichrome/tri-band image, which often produces more natural-looking colors (for example, the sky is still blue) and also there is a wavelength-color relationship. UVP member Bernard Foot has experimented with the technique some years ago, and I have already tried it before. Other people (notably UVP member OlDoinyo) like to render white-balanced UV photos in BGR (swapping the red and blue channels), which also produces blue skies and a different color palette. Since I have a color camera, the images I take when making a TriColour image have colors, which I normally get rid of to make the channels. If I stack those images instead, I can simulate the raw image taken by a camera with an approximately flat response between about 310 nm and 400 nm, and with sunlight having a uniform spectrum too. This never happens in real life, even with a UV-dedicated lens. The interesting part is comparing the resulting colors with those of a normal UV photo. The equipment I used is the usual one: full-spectrum Canon EOS M, SvBony 0.5x focal reducer lens and the following filters: TriColour: Blue channel: double 310 nm Chinese bandpass filter + ZWB1 (2*2 mm) (the ZWB1's are not necessary, but I used them anyway); Green channel: BrightLine 340/26 filter + ZWB1 (2*2 mm); Red channel: BrightLine 387/11 filter + Chinese BG39 (2 mm); Standard UV: ZWB2(2 mm) + Chinese BG39 (2 mm); Visible reference: Chinese BG39 (2 mm); The technique used to make the TriColour images is also the usual one, described here. The major difference is that I took multiple 310 nm exposures this time and stacked them taking the darkest pixels (5 in both cases). As for the raw color stacks, I set the brightness of each image to be about the same by eye and stacked them. Also, following Andy's advice last time, I raised the brightness of my images and the contrast in the TriColour stacks (also because the contrast in the original channels was removed in PhotoNinja during the processing). The visible and UV references are white-balanced in-camera, the raw stacks were white-balanced in PhotoNinja. I used both UV-lavender and UV-yellow subjects. For the lavender, I picked three items with varying degrees of lavender: a magnifying glass on the left (transparent at 387 nm, mostly transparent at 340 nm and opaque at 310 nm), almost colorless; a white LED lightbulb in the middle, and a plastic lens on the right (mostly transparent at 387 nm but opaque at 340 nm and below, which shows a strong blue-purple color). Visible reference: Standard UV: White-balanced raw UV stack: As you can see, the color palette didn't change much, but since here the shorter UV wavelengths contribute much more to the image, the magnifying glass is noticeably darker. In general, objects with a pale lavender color got a color boost. UV TriColour: Here the color palette is obviously richer, with the color giving a good indication of the transmitted/reflected wavelengths. Standard UV, BGR: Compared to the TriColour rendition above, only the plastic lens on the right looks similar, while the color deviates more for items with a flatter UV response. For comparison, here's the raw stack, in BGR version: ...and now for the yellows. Here I used a 3 mm thick ZWB1 filter on the left, and a 2 mm thick ZWB2 filter on the right. Visible reference: Standard UV: Here the colors look similar, with the ZWB1 filter being slightly greener, as expected. Also the paper tissue I used apparently contains UV-absorbing fibers. White-balanced raw UV stack: Here things get weird. The ZWB1 filter got orange, which is a bit different from its normal color. Also, and this was expected, the difference in color (hence transmission) between the filters is more evident now. UV TriColour: Standard UV, BGR: UV stack, BGR: Raw or .tif files are available.

Today I would like to report something about UV sensitivity and the color differentiation of my camera bodies. First to the cameras: It is a Canon EOS 500 D (in Japan EOS Kiss X3, in North America EOS Rebel T1i), an APS-C camera with approx. 15 MP, and a Canon 6 D, a full-frame Camera with approx. 20 MP. I de-filtered the 500 D according to the instructions from Gary Honis (http://dslrmodifications.com/rebelmod450d1.html). As a replacement for the removed filter, I used a quartz cover glass from microscopy (cut to size). The 6D I had de-filtered professionally (http://www.astro-modifikationen.de). The filter structure of the 6 D is more complex. Only the top two (dust vibrator and original white balance filter) of the three filters were removed. One protective glass remains on the sensor. Unfortunately I have neither a calibrated spectrometer nor a suitable monochromator for measurements. Of course I am interested in individual measurement curves for filters and lenses as well as sensitivity curves for sensors, but – on the other hand - for photography only the interaction of all parts is relevant to me. This is why I have chosen the following method for my comparisons, which comes very close to the real situation when photographing in sunlight: I used the midday sun as a light source. The light falls through a slit onto a grating (made from a DVD). I then focused the spectrum generated in this way through my UV filter (here: Baader-U) and the lens (50 mm magnifying lens, mounted on a suitable helicoid) on the camera sensor. The spectra can be seen twice each, above with the camera-internal white balance to sunlight, below with white balance from reflected sunlight to matt PTFE. So I can see which parts of the sunlight are used in which intensity for the picture (with a white motif) and which wavelengths correspond to which false colors. The Fraunhofer lines disturb the overall impression a little, but also allow an internal wavelength calibration. Canon EOS 6 D-FS Canon EOS 500 D-FS Conclusions The sensitivity of the EOS 6 D-FS does not reach as deep into the UV range as the 500 D-FS. This is probably not due to the sensor, but to the remaining filter glass. The color differentiation is stronger with the 500 D-FS. The longer wave range is shown more violet with the 500 D-FS and more bluish with the 6 D-FS. The shorter-wave area is shown greener on the 500 D-FS than on the 6 D-FS. Overall, with this method I can clearly see which filter-lens-camera combination can display which UV area. In further posts I can show lens comparisons and comparisons with other light sources.

It was a relatively sunny day and I decided to test recently converted camera. Here is a photo of swans in Newstead Abbey, Nottinghamshire. Gear used: Sony A7, El-Nikkor 100mm, S8612 x 1.5mm, UG1 x 2mm. This is my first UV experiment so perhaps WB is not very accurate. I used DNG Profile Editor, Lightroom and I applied white balance dropper on asphalt. For some reason PTFE (10mm) did not work as a white balance source that day.

My white balance target is a thin board wrapped in plumber's tape. Performs well enough, but it is fragile. Would it work to place the target inside a CD case and take the reading thru the plastic? CD cases are supposed to be transparent to UV. Thanks, Doug A

Target UV & UV Grey Card, UVA Fluorescent Standards, Colour Checker. http://www.imagescienceassociates.com/mm5/merchant.mvc?Screen=PROD&Store_Code=ISA001&Product_Code=TUVUVGC&Category_Code=TARGETS I would like to have something like this, but the cost / benefit is unfavourable. I would love to know the minerals used ?

Hi, I just wonder if it is possible to achive auto white balance in-camera (Nikons are known to cowardly refuse to set white balance from IR/UV/FS photos). I want to be able to do multispectral photo with just one filter - ideally that would include visible & IR + as a bonus, possibly, just a bit of UV. Images without filters are "too red" for Nikons to auto WB, so my idea was to add a filter that will block most red around 650-750 nm to make it able o do auto WB. Hoya blue & green filters seems to be good candidates: - Hoya C4, C8, and especially C12 hav a very suitable transmissions IMHO: https://hoyafilter.com/product/c8_blue_cooling/ (C12 seems to be cutting visible quite a lot but it passes UV which is good, C8 looks best at the first glance, but it may just start cutting red on too long wavelengths, C4 seems least interesting and also cuts UV). - Hoya X0, X1: https://hoyafilter.com/product/x1_green/ (both cut UV :-( but X0 passes a lot of IR and may be just enought to auto WB). The question here is: does anybody used any of those (or Nikon X0, X1 filters) on a Nikon full spectrum body and was able to auto white balance? I always prefer to shoot many photos in JPEG than doing RAWs and then converting them - auto white balance in-camera woudl help a lot with spot-checking if my settings are OK, also could have some fun artictic colors - I always prefer to shoot handheld and close as much as possible to a normal mode. If such X0 or C8 would make it possible, I would order them and use for my full spectrum shots (ideally I just want to keep as much as possible IR and UV and surpss just enough red channel to be able to AWB).

Hello, I recently realized, by accident, that my Canon EF-M 22mm pancake lens appears to let as much UV through as the Soligor 35mm f/3.5 and El-Nikkor 80mm f/5.6. That was an interesting surprise, since the EF-M lens provides much sharper pictures. In order to compare them, I took these pictures after doing an in-camera custom white balance with the Soligor lens on a PTFE sheet. All shots were taken with a LaLaU filter with 1600 ISO, their respective exposures were determined by the camera light meter in manual mode and were taken within minutes of each other under similar illumination. Natural UV light is low here at this time of the year, so the exposure times were long. The subjects are a plush plant (no wind blurriness here!) and a grapefruit. This is with the Soligor 35mm f/3.5 0.25 second This is with the El-Nikkor 80mm f/5.6 0.60 second This is with the EF-M 22mm f/3.5 0.50 second This is with the EF-M 22mm f/2.0 0.125 second The EF-M 22mm appears to transmit UV well overall, but it causes a shift in the white balance of the picture and I wonder why. Could it be because it blocks shorter wavelengths that the Soligor and El-Nikkor allow through?

Note: Several posts from JMC deal with the same or very similar questions (e.g. https://www.ultravioletphotography.com/content/index.php?/topic/2813-camera-sensitivity-chasing-ghosts-in-spectral-sensitivity In the following I show an investigation with sunlight, not with a monochromator. This means that the result is not so universal, but the applicability to UV photos in sunlight is quite useful - I think. I recorded the solar spectrum at noon when the sky was clear. For the original RAW recording, I carried out a WB against PTFE inside the camera. On the left side, the spectrum is mainly limited by the presence (absence?) of light. The lens transmits artificial light down to almost 320 nm. On the right side, the light is limited by the filter. Here it was a DUG11x from Schott (made available to me by ITOS 2015, which was selling Schott glasses at the time). In the RAW converter (DxO PhotoLab 3) I developed two jpgs from it. All corrections are switched off, I just adjusted the brightness so that no channel comes over 255. I chose the generic setting together with the color mode "neutral, realistic tonality, gamma 2.2" as the color profile. This gives me the yellow to blue tones shown here in general against PTFE. 1. WB on Sunlight The picture appears in brown, pink and purple tones. 2. WB according to PTFE measurement Here you can see the usual yellow and blue tones If you plot the R, - G and B values as a function of the wavelength in the spectra, you get the following distributions (left side "WB sunlight", right side "WB PTFE"). The Fraunhofer lines are a bit annoying here, the curves look "unsmoothed" but the most important things can also be seen. You can see very well in the "WB sunlight" graphs that the red pixels have the highest sensitivity in the entire spectral range. The green sensitivity is much lower and the green pixels only react again from approx. 380 nm. The blue pixels only react to light up to approx. 365 nm and are also significantly less sensitive than the red pixels. Below 365 nm, only red and green can be mixed and there are orange and brown tones. In the range from 365 to 380 nm, all three types of pixels react to the light. Achromatic mixed colors are possible here. Above 380 nm, only mixed colors of blue and red are possible. If you now carry out a WB to PTFE, then above all red is attenuated and green (and blue) is increased. The typical false colors can now be created. At around 370 nm, all three intensities are the same. So here an area is shown achromatic. This is the transition area from yellow to a not fully saturated blue-violet.

The following experiment shows by way of example that false colors are possible even with narrow-band illumination using LEDs and that the transition from yellow to blue is not always at the same wavelength. Experiment To investigate, I recorded and compared the spectra of the light sources using a simple method: LED flashlight, metal slit (1.5mm), 1m distance, DVD grating, Baader-U plus 2mm QB21 (to avoid NIR artefacts), f 50mm enlarger lens, Canon 500 D-FS WB in each case on PTFE, identical color profile, which produces yellow and blue false colors with sunlight. LED flashlights: peak values at about 375 nm and 405 nm. Comparison/wavelength calibration: sunlight. RAW conversion: DxO PhotoLab 3, WB sunlight, color rendering "generic" plus "neutral colors, neutral tone, gamma 2.2" Results - Even with narrow-band light sources, yellow tones are shown in the shorter-wave range, blue-violet tones in the longer-wave range. - The position of the color transition from yellow to blue is therefore dependent on the light source. - The color rendering is slightly different even with identical color profiles if the used spectral range is different. Additional comment The Baader-U cuts off at below 400 nm. Accordingly, only the outermost part of the short-wave flank of the emitted light of the 405 nm LED is shown. Since only very little light is emitted here, the exposure time for the 405nm LED is one second - for the 375nm LED it is only 1 / 350s.

Hi, I've read white balance topics (globally approved on this forum), I want to achieve a specific goal that's why I'm asking. - I can't use any photo or PTFE/grey concrete as a white balance source for Nikon (also known on this forum). - I know that I can shoot with whatever setting because NEF files always contain raw data, and white balance used by camera is just a hint, we can always get 16bit data for each pixel, even before Bayer algorithm (so each pixel will have 0-65535 value for each RGGB channel). 1) How can I white-balance Nikon NEF file to match standard colors used here - there must be some set of approximate factors for each R, G, B channels to apply to a RAW file right? 2) I can always just auto-white balance a given shot, so its average color is gray (for all pixels) - I have scripts that do this (I'm a programmer). All I want is a script that would white balance NEF file given as a command-line argument. I have dcraw, ImageMagick, gimp programs installed - need to build a script that would auto balance to widely accepted color forums. Currently I'm using my own script that "auto-white balances" (averaging NEF to gray), I don't think this is correct, I believe I need to just apply a custom R, G, B factors just after Bayer algorithm is applied on the RAW data (speaking about my non-debayered camera, monochrome one is simple - I just get every pixel before Bayer algorithm and save - that also make resolution up to 2x higher - in practice just a bit better). What I do now for bayered NEF's is: "dcraw -H 1 -a -q 3 -T filename.NEF" - "-H 1" - do not clip light - "-a" - average white balance - "-q 3" - inerpolation detail [0-3] - "-T " save as TIFF instead of PPM If I have a white balance "source" file I can also do: - color=`convert white-balance-source.png -resize 1x1! -modulate 100,100,0 -format "%[pixel:u.p{0,0}]" info:` - echo "White balance color $color" - convert filename.png -colorspace sRGB \( -clone 0 -fill "$color" -colorize 50% \) -compose colorize -composite -colorspace sRGB -quality 98% output.jpeg For mono, I can save total raw data with each pixel RGGB raw 16bit signal via: - "dcraw -4 -o 0 -D -t 0 -k 0 -H 1 -T filename.NEF": - "- 4" - linear 16bit grey - "-o 0" [0-6] possible, 0=raw - "-D" - document mode, no scale, total raw - "-t 0" - rotate=0 (no rotate) - "-k 0" - black cut level 0 - "-H 1" - highlight clip mode 1=no clip - "-T " save as TIFF instead of PPM Again to sum up : I need a script to auto balance Nikon NEF file and save as PNG/JPG whatever (file from full spectrum camera, but with Bayer RGGB matrix present, assuming it registers only UV <= 400nm, no IR leaks) - probably maybe just R, G, B const factors?

For various purposes I was looking for a (low-cost) color card for the UV-A range. The question arises because I don't have beautiful flowers all year round. So I looked for materials that appear colored in the UV image. Many plastic samples appear purple, so they prefer to reflect longer-wave UV light. Some textiles appear yellowish or greenish, especially those that appear yellow and orange in the VIS light. Apparently they prefer to reflect shorter-wave UV. I glued a few samples to a piece of plywood along with a piece of PTFE and a piece of black leather (seems to be black in all wavelengths). Here are a few photos (unfortunately not in the sunlight, as the cloud cover is currently too thick): 1. Canon 500D-FS, enlarger lens, Osram Lumilux deLuxe 950 and white balance against the good old Kodak Graycard. 2. Canon 500D-FS, enlarger lens, Baader-U with a QB21, Xenon lamp (Eprom-Eraser ZAX Quick-E II) and white balance against sunlight. First image native, second image color-enhanced. 3. Canon 500D-FS, enlarger lens, Baader-U with a QB21, 370 nm LED with UG-1. First picture with white balance against sunlight - everything appears yellow here. Second picture with white balance against PTFE - everything appears nearly achromatic here. Sure, the light source is also pretty "monochromatic". But a slight color differentiation can still be seen on closer inspection... Note: Nice how you can see the glue residue in the UV. Question to all Who has discovered materials that only reflect in deep UV-A (appear as pure green)? Klaus Schmitt reported on a Zinnia species (https://photographyoftheinvisibleworld.blogspot.com/2015/07/mexican-zinnia-zinnia-haagenea-in-deep.html). But I am interested in a permanent substance (mineral, pigment, polymer, ...). .

I have now some Alabaster, Selenite, Gypsum, call it what you may.... For discussion on its use as a White Balance Tool ? Three photos, please forgive the carpet inside the camera / lens First is the a visible light of the Alabaster egg on top of a, switched off, light. Second is with a visible light camera of an Alabaster egg on top of a lit 365nm LED light. Third is with a full spectrum camera with a Quartz lens, of an Alabaster egg on top of a lit 365nm LED light.

https://www.fluomin.org/ One thing led to another today and I fell down the rabbit hole for a long time....... Soooo, along the way I read that alabaster fluoresces white under 365nm. How white? It did not say. But it occured to me that placing a hunk of alabaster (or other white fluorescing mineral) in a fluorescence photo might possibly serve as a white balance object. Trying to WB fluorescence photos has been an on-going topic here on UVP for the last few years. The WB standard for fluorescence is quite expensive, so now I'm hoping a chunk of some mineral would be useful and much cheaper. Here is the place to make a list of white fluorescing minerals under 365nm. I've never heard of most of these. There may be colour casts to the fluorescence, so there would need to be testing. http://www.fluomin.org/uk/searchbycoloruk.php