Search the Community

An interesting paper in the current issue of PLOS Biology: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002444 I haven't had time to read it fully yet, but the illustrations look good!

Just had a storm pass through recently that cleared the air and left some snow on the mountains so I thought I'd do a UV-VIS-IR comparison series today. The hills are about 12 miles away and the mountains are about 40 miles out. All shots were taken with a Sony A6000 FS-converted with Sirchie 60mm quartz lens. UV Filter- Baader-U VIS Filter- Kolari UV-IR Block IR Filter- Zomei 950nm The lack of edge sharpness is really obvious in the VIS shot because of the much wider spectrum captured. I should have maybe used a green filter to limit the spectrum enough for this all-quartz lens to get a sharper image. The Sirchie lens was designed for narrowband forensic work and not for this kind of photography. These are reasonably lined up well enough to do a blink comparison if you download them. The reduction of haze in each step due to declining Rayleigh scattering of the longer wavelengths is easy to see here.

Isn't this beautiful.

After spending a year or so experimenting with IR photography I obtained a Tiffen 18A filter for UV photography. It had a similar pass spectrum to the modern day ZWB1 filter with maybe a later cut-on above 300nm. They both have a good UV-A passband but also an IR passband that extends into the deep red. I decided to use a non-panchromatic film (little or no red sensitivity) that was just sensitive to blue & green to get a 'pure' UV image. I had a roll of Kodak SO-410 film which was used for photomicrography and imaging phosphor screens like oscilloscopes and radar screens that were blue or green. I did several VIS/UV comparison shots on an old Agfa rangefinder camera to see what the differences were. To keep the bandwidths about the same I used a #47 blue filter for the VIS photos. Unfortunately I was unable to locate the matching UV & VIS negatives for most of them. Here is one set from my photo album (remember those?) that I can't find the negs for. Left pic is with the #47 blue filter and right pic is with the 18A. These show a mountain about 2 miles away that gets very hazy in the UV pic. Apparently evidence of the extra Rayleigh scattering of UV. The only set of matching VIS and UV negs I could find are the recent scans I just made below. First one is blue VIS and second one is UV-A. If you download these last two pics you can do a 'blink' test and see the different haze effect between Blue and UV-A more clearly. Aside from a few indoor tests with spectrum tubes shortly afterwards I lost interest in UV photography. Compared to the general darkening and increased haze in UV, IR photography offered haze penetration and a magical brightened rendition of vegetation. The adventure of color IR film was also a huge attraction. Only in recent years did I get interested in UV photography again thanks largely to this site and the many contributors here.

The following experiments are inspired by the findings of @Christoph Here is a series of pictures with my full spectrum canon 1200D and a stack of these three filters : Midopt Triple bandpass 550/660/850nm Lee "Flesh pink" gel GRB3 from Tangsinuo The transmission curve of the three filters combined should look something like this : Both the green and the IR spike are heavily filtered. When the TB is used alone, it seems to suffer from a very weak red transmission : without the GRB3 the red channel records as much (if not more) IR than red, requiring IR subtraction of 100%. The green spike transmission to the contrary is very powerful. To the eye (at least mine) the filter is green. I'm not sure how bright humans are able to percieve red at 660nm, its pretty deep already. I then decided to reduce the transmission of IR and green equally to give room for the red transmission. The GRB3 is used to minimise IR contamination in the RED channel and the Lee gel is used minimise green contamination in the blue/IR channel and to make it more or less match the level of output of the red channel. The blue channel stays very underexposed compared to the two others, and is brought back in white balance (pretty extreme : lower than 1900Kelvin). The exposure value with these filters ranges from 1/50s to 1/100s in sunlight at f5.6, 200iso. It's a very dark combo. All the pictures are channel swapped in Resolve from the camera Jpegs, the process is video ready. No saturation was added and zero IR substraction is needed. The fact that IR transmission is cut by 90% by the GRB3 causes some green leaks to be percieved in the Blue/IR channel. This leads to the need to apply a hue correction to the sky in order to make it look properly blue and not purple-ish. This process is simple and non-destructive. The original color of the sky after channel swap : Important notice : The channel swap causes a significant decrease in contrast and micro-contrast. For a moment I thought this was due to the Jpeg compression but it is not. Do you remember this law ? Y = 0.1 Blue + 0.6 Green + 0.3 Red It is actually crucial in understanding why the images look better unswapped. It describes how the human eye is sensitive to luminosity. The green value is far more decisive in the percieved brightness of an object than the red and blue values. A quick exemple Unswapped image : Swapped image : it looks less detailed and dynamic. The contrast beetween the bright grass and the dark trees is lessened Swapped image but with the "preserve luminance" box ticked : the image is sharper and more alive. (Click on the image and use the viewer to compare both instantaneously.) Explanation : The grass in the unswapped image appears turquoise. Let's make it cyan for the sake of clarity. The trees appear blue. Cyan RGB values are (0; 255; 255) Blue RGB values are (0; 0; 255) The minimum luminance(Y) is 0 and the maximum luminance is 1. Y(cyan grass) = 0.1x Blue(255/255) + 0.6x Green(255/255) + 0.3x Red(0/255) = 0.7 Y(blue trees) = 0.1 x B(255/255) + 0.6 x G(0/255) + 0.3 x R(0/255) = 0.1 in the unswapped image the contrast beetween the brightness of the trees and the grass is important : Y=0.1 versus Y=0.7. Now, let's do the same for the swapped image where the grass is magenta and the trees are red. Y(magenta grass) = 0.1 x B(255/255) + 0.6 x G(0/255) + 0.3 x R(255/255) = 0.4 Y(red trees) = 0.1 x B(0/255) + 0.6 x G(0/255) 0.3 x R (255/255) = 0.3 in the swapped image the contrast beetween the brightness of the trees and grass is less important than in the original image (Y=0.3 versus Y=0.4) In this chart the colors are ranked by luminance. white Y=1, yellow Y=0.9, cyan Y=0.7, green Y=0.6, magenta Y=0.4, red Y=0.3, blue Y=0.1, black Y=0 As you can see here the brightness of Magenta and Red is very close as opposed to cyan and blue that are very far apart. So that's why channel swapping sometimes makes the image lose quality. A solution to this is to tick the box "preserve luminance" in the channel mixer. It doesn't work in every situation since it makes the yellow objects turn way darker, leading to an unnatural look. Ticking the box also makes the sky way brighter. It's a tradeoff that has to be made for each individual picture. In the selection I posted above, a few have the box ticked and most don't.

I have been taking a lot of photos lately. This time I decided to investigate a pair of cucumbers. I illuminated them with a halogen spotlight, which emits enough light for IR, visible and UV. IR tri color is using my GRB3 method UV is taken with a ZWB2+QB39 stack (which surprisingly does not leak significantly, even with halogen) I will also be including the individual pictures if anyone else wanted to take a shot at processing them (please, do post). I'd especially appreciate if someone managed to stack all 7 channels continually. I only could stack them by binning the visible and the IR part of the spectrum together. The pictures are in full hd so if you still have a 1080p display, you might want to enlarge. visible IR tri color 850nm+720nm+red Aerochrome simulation GBUV full spectrum individual color channels: 950nm longpass ~850nm band ~720nm band red band green band blue band UV band (400-350nm) I also decided to stack the images in Photoshop and pick the range stack mode, I got interesting results. All of the bands stacked: All of the bands except for UV stacked: IR only stacked: IR only stacked (normalized): Bonus: IR stacked, normalized and processed with Topaz Denoise AI: Here's the IR range mapped on the visible image: Here's the range between 720 and 850 bands mapped on the visible image:

As you know, all cameras react differently to IR light once they are converted to full spectrum. I don't know if this is really well understood so I wanted to start a topic and have your opinion about it. I just got the Sony f828 (the camera that can be converted to full spectrum with just a magnet) and I can now compare its fullspectrum colors to my Canon. Canon 1200D, white balanced full spectrum colors, no additional filters : Sony f828, white balanced full spectrum colors, no additional filter : The pictures were white balanced and saturated from the RAW files in Lightroom. The two cameras are pretty far apart as we can see from these pictures. They are also pretty far apart in terms of technology : the first is an 18Mpx CMOS and the second is a 20 years old 8Mpx CCD one of a kind RGBE sensor. Sony camera are known to not perform as good as Canon with the IRchrome filter. The images above indeed show that this Canon camera has a predisposition to record IR in the red channel compared to the Sony. Now do more recent Sony cameras produce blue SOOC like this one does ? I don't know... Maybe the sony users here can help me from their experience.

Today I took a few UV/IR photos of some people in my university, including the arm of one girl who is covered in freckles (or similar). Also I used a Helios lens I have, it passes UV to about 340-350 nm and so it should behave similarly to a Canon 40 mm f/2.8 pancake. I had a PTFE square, but I didn't use it for these photos. Photos rendered in black and white. Full-spectrum Canon EOS M, Helios-44M-5 (stopped down, maybe at f/8). - UV: ZWB2 (2 mm) + Chinese BG39 (2 mm); - VIS: Chinese BG39 (2 mm). There should be a negligible amount of UV contamination; - IR: Hoya R72. UV (ISO 800, 1/2 s): VIS (ISO 100, 1/500 s): IR (ISO 100 1/500 s): Tricolour/composite (blue: UV; green: VIS; red: IR):

Hello, my name is Fedia, I'm 31 and I spend lot of time creating images through digital photography. I'm stoked to be able to join this forum since it has been an incredible ressource without which I couldn't have developed the techniques I use today. I have talked to some of the people of this forum on other platforms, used their advice and want to thank them also. I've been doing photography since 2014 when I entered film school. I got my first full spectrum camera in the fall of 2020. Even before I got into full spectrum photography, the main thread I explored was color, that I achieved through filters or extreme white balance settings on regular cameras. Even today with full spcetrum photography I don't really use softwares. I try to do everything in camera. Therefore I exclusively shoot jpegs and only work contrast in Lightroom. I never opened Photoshop. I am a big technical nerd I guess you could say, but the truth is my relation to technicity has a lot to do with my artistic sensitivity, both are entangled. I have a lot of ideas of subjects to discuss on this forum so I will post about them in the near-future. But for now I figured I will post some of my photos to introduce myself. Every one of the following photos are the result of a different filter combination with no color processing outside of the body of the camera. I will precise the camera and the filters each time. Canon 1000D full spectrum + Lee "CID to Tungsten" Canon 1000D FS + Lee "loving amber" + db850 Canon 1200D FS + DB850 + Lee "Liberty green" Canon 1000D + unknown dark pink gel Canon 1000D + Lee "steel blue" Canon 1200D FS + Lee "peacock blue" + GRB3 Canon 1200D FS + hoya 80A + hoya x(0) + cokin 089 (warm diffuser) Sigma DP1s FS Sigma DP1s FS + Hoya 80C Sigma DP1s FS + GRB3 Bonus : Sigma DP1s FS no filter. If you want to see more I have an instagram : https://www.instagram.com/fedialebarboc/?hl=fr And a tumblr : https://fedialegrill.tumblr.com/ Thanks again, Fedia.

Multispectral photography was one of the things I was really excited to try when I finally got a UV-pass filter, and the other week I finally had some free time to go out and try it Editing took took a pretty long time (definitely a much different workflow than I'm used to), but I'm very happy with the results! I love the colors of the brush in the foreground, I think they're more nuanced than regular false-color IR with a Red25 (or similar) filter. I want to try this again on a clearer day, since the haze is definitely not being kind to the shorter wavelengths IR -> R Red -> G UV -> B Raw frames processed in Darktable, then mostly aligned with the Align_Image_Stack tool from Hugin (but the left part of the panorama needed some extra hand-alignment in Gimp since Hugin couldn't do it perfectly). Then composed in Gimp, into Hugin to stitch the two together, and finally processed further in Darktable Taken on a FS Sony A5000 with a Sigma 19mm f/2.8 DN And here are the individual IR, Vis, and UV shots: Vis (TSN575): IR (850nm): (it always amazes me how well IR is able to punch through haze!) UV (ZWB2 + TSN575):

I recently aquired a planetary CMOS camera, the ZWO ASI678MC. Here is my planetary rig with 300mm f/4 PF and stacked 1.4 and 2x converters to provide an 840mm f/11 lens. This has an IMX678c 7.7mm wide back illuminated chip in 4K resolution and 2um pixel pitch. It has an excellent IR response. Example with an Antlia 685nm IR-pass filter and Nikon AF 20mm f.2.8 lens: but the ZWO chart is a little less clear on what happens on the the UV side: The sensor has an AR coated protective window. The curve above is with this window in place. A chart of this window's transmission spectrum in the specs of another ZWO camera model gives a hint that deep UV responses cannot be expected: However I happened to have a 20mm diameter 2mm thick ZWB1 filter, which by itself of course leaks IR, but found a QB39 IR cut filter, also in 20mm diameter 2mm thickness in ebay seller tangsinuo's store. The transmission is only given for the 1mm thickness: Then I found a 1,25" "moon filter" from Agena Asto that had a donor cell with a wide rim. The 20mm filters had a loose fit in it, but worked with the ZBW1 closest to the sensor and retaining ring that the slightly narrower QB39 would slip into; scotch tape was used on the edge as spacer between filters to avoid newton rings. Then I have a Cassarit 50mm f/2.8 lens that way back was given to me as part of a corroded camera in parts in a plastic bag by late Professor Krog in Oslo. As the lens did not show signs of water damage, just needed cleaning, my guess is that the camera succumbed to a humid tropical climate, possibly when he participated in the 1967 Alpha Helix Expedition in Amazonas. While it is not listed among the better classes of UV lenses, it is a triplet with old coatings. Visual response with a ZWO UVIR cut filter, all of these were captured as small videos with FireCapture and stacked in Autostakkert, Small versions are with unadjusted colors before using a gray control point on the upper right qwhite patch in the left panel. I try to keep aperture of the Cassarit at f/5.6. The UV-IR cut filter is designed for astro work and has an enhanced red respons up to above 656 nm. Light souce is my nightrider Lumen 900 bike light: Then with ZWB1+QB39 filters only with my Convoy S2+ 365nm and Tank 007TK-566, both with what is likely ZBW2 filters on the front at 4m distance from the target. 200ms exposure and Gain 320. Some preliminary tests indicate that a Gain of 100 corresponds to ISO 100 sensitivity and from there approximately a dobling of ISO for every increase in gain of 50. So this would be about ISO2000: Then the same combination in sunlight, 200ms gain 228: It is notably different color responses, with yellow-green dominating with 365nm source and sunlight colder, which I assume is due to dominance of longer wavelengths in sunlight that records more in the blue channel. To test effectiveness of the filtering here is IR pass 685 nm 1ms exposure, Gain 26: then ZWB1+QB39, 192ms Gain 26: Finally ZWB1+QB39+ IRpass 685nm, 1s Gain 405 - This would be about 10 EVs below the UV exposure if my calculations are correct: [There is a light leak at lower right as the IR pass filter was mounted to a snout that was just held onto the front of the Cassarit.] So I will conclude that for my limited practical purpose, IR leak is not a problem with this combination. A couple of days ago to my delight the first dandelions showed up outside our department at the university to allow a practical test. The initial try was handheld as my tripod was at home and it is recorded on my phone with the ZWO ASICap app, so here is just a low res overview, ZWB1+QB39 : I picked up one dandelion and brought home for a more proper test. The best result appeared with a cloud diffusing the light. ZWB1+QB39, f/5.6, 517.5ms exposure, Gain 200 (corresponding to ISO400), 12 bit mode, 32 frame .ser raw video in Firecapture, stacked the 8 best, WB adjusted according to another capture on a Teflon tape wrapped plastic case where histograms were equalized. Gamma adjusted to 2.2 in irfanview (as the video is linear), with following increase in contrast and saturation (click for larger version): Not bad for a lens that is possibly 60-70 years old and never designed for UV captures! That is all for tonight, more to follow...

My interest in light didn't end when I studied laser physics in Hungary and didn't start in the UK while developing high power lasers. I'm now in Switzerland focused on the infrared part of the spectrum, NIR, SWIR, hyperspectral, multispectral. Continously collecting light: line and area scan cameras, optical simulations, spectrometers, slit goggles.. I'm DIY-optics (dot com) himself. ;) You have a very nice community here, I appreciate being a new member. Hello Everyone

Casswell, T. (2022) Gazania rigens (L.) Gaertn. (Asteraceae) Gazania. Flowers photographed in ultraviolet, infrared and visible light. Also with multispectral stack. LINK Location: 17 June 2022 Australia Collected from a street garden adjacent to the beachfront at Coolum Synonyms: several -- see Reference Other Common Names: Treasure flower Comment: This species is recognized as a weed in some areas of Australia, however it is widely used for a groundcover in suburban street gardens, median strips, traffic islands, etc in south eastern Queensland due to its hardy nature and prolific flowers in a variety of colours blooming nearly all year round. Two samples were taken and placed in a water filled vase approx 20 min after collection. Each was imaged using Baader U, Kolari U, Kolari Hot Mirror V2 & a generic 650nm infrared filter. All eight image runs were focus stacked. An attempt was made to combine infrared (R), visible (G) & UV (B) into a multispectral image (mantis shrimp vision?), which proved difficult due to the dynamic nature of the flower given its circumstances. Reference: 1. Wikipedia (18 June 2022) Gazania rigens. Wikimedia Foundation, San Francisco, CA. Equipment: Converted Canon EOS R5 EL-Nikkor 105/5.6. Baader U, Kolari U, Kolari Hot Mirror V2 & a generic 650nm infrared filters Technique: UV, visible & infrared colour balanced using a white PTFE sheet with exposure dialled down to avoid any RGB channel clipping. Focus stacked using Helicon Focus 8. ISO100, f/11 for all shots. Multispectral - aligned using PT Gui with manually placed control points Yellowish White Sample: Visible light, t = 1/100s UV (Baader U), t = 5s UV (Kolari U), t = 5s (some highlight clipping) 650nm Infrared, t = 1/80s Multispectral using the Kolari U for UV (blue channel) Yellow Sample: Visible light, t = 1/80s (slight overexposure) UV (Baader U), t = 8s UV (Kolari U), t = 8s 650nm Infrared, t = 1/80s

I know this is primarily a UV forum, but having put together my ZBW2 UV filter stack with some cheaper 3rd party alternatives, I've come to realize that I am sorely lacking in overall knowledge regarding light modification techniques and filters. After seeing a post on here showing the Kolari IR Chrome filter I use could be recreated by stacking 3rd party filters together, I tried looking around the forum to see if there were any other interesting combinations or filters. I noticed there isn't a pinned thread or compendium dedicated to comparing various IR and other filters. A dedicated thread/page would be extremely useful for new members such as myself!

It's always amazing what some filters and a little patience can do, once the camera is put on a sturdy tripod. For this capture, I combined captures in UV, visible light, and IR, using the Nikon D200 and a very old 55mm f/3.5 Micro-Nikkor lens. I think the result was nice, but your mileage might vary. The old Micro-Nikkor does not transmit deep into UV, but that hardly matters in this setup. The scene should be familiar to Nordic people; comprising a tidal pool (Norwegian 'hellkar') on a glacially-scoured coastal rock face (Norwegian 'svaberg'). I believe the designations are quite similar in both Norwegian and Swedish languages, those two countries (+ Finland) where such rocks are common on the coastline.

I did this yesterday impulsively and it has been one of the most fun and rewarding projects I've done in a while. That's why I decided to share it with you today. I took three total images of the same subject, from the same perspective, with different parts of the spectrum filtered. The subject is a random plant my mother owns, a PTFE sheet, and my RGB LED strip controller. I wanted to use it as an improvised color checker, but it didn't work out so well since the actual dye containing layer is covered with UV- absorbing plastic from what I see. (lightsource for each image was just sunlight) Here are the images: visible IR (720nm) UV (ZWB2 + QB39) - this was shot with only the light coming through the window, it is winter so opening all the windows was not an option, but it seems to have produced an ok quality image regardless, only downside being that the exposure time needed was long, around three minutes. The images at this point are perfectly aligned, you can download them and stack them yourself, they should fit perfectly. And it was a lot of work to align them I admit, photoshop failed at doing it properly so I had to do it fully manually. Worth it. Prior to aligning, all the images were rendered using darktable, with light balance set on the PTFE sheet, most processing options turned off with the exception of highlight reconstruction in the UV image. That is why they are so flat, nothing should be blown out here. Upcoming images are more edited. I used AMaZE + VNG4 as my demosaicing method. In this next portion, I will showcase two trichromes I produced using this data and their color corrected variants. IR-R Visible-G UV-B trichrome As you can see, this image looks a little weird, I think it is because the illumination in UV was not the best, causing extreme contrast, though I'm not entirely sure if the yellow cast would go away if I brought the whole setup on open sunlight, maybe I am just unlucky and almost all the materials visualized absorb significantly more in UV, including my grey wall paint. I took the liberty of color correcting the photo to bring out some color details. Looks a bit less washed out, not perfect but sufficient. Next I have a GBUV stack. I extracted the green and blue channels from the visible image, mapped them to red and green, then I mapped the UV channel to blue. Once again, the image is washed out, so here's the color corrected version. Up next I have a few things that might not be of more "scientific" significance, but I think they're really fun. For this I used the photoshop stack mode function for smart objects. I used the maximum, minimum, median and mean functions. https://helpx.adobe.com/photoshop/using/image-stacks.html On this website, you can find a full list of possible stack modes that I could use plus their practical and mathematical explanation. I ended up not using entropy, kurtosis, range, skewness, standard deviation, summation and variance. If anyone would like to see these please do tell me so I can add them. They're mostly just a jumbled mess of seemingly random colors or completely white though. Keep in mind I normalized and edited the images a bit, so for example the upcoming minimum isn't extremely dark. If you want to see the unedited versions, again please do tell. stack mode minimum stack mode maximum stack mode mean stack mode median And the last series of images which I think are the most interesting. They are the IR and the UV images layered with the visible image in "color" mode. So that the image keeps the texture of the UV/IR image but the colors are normal. IR And my favorite, UV. I think the UV really is an interesting aesthetic that could perhaps be used in product photography or something, I dunno, just find the image really interesting to look at. That's all, I'm about to go watch a movie, I hope you liked my post, see you in the comments!

Based on a discussion here I was really intrigued by the graph shown for silver with the strong dip in reflectance around 320nm. I ordered a sheet of silver leaf from ebay (edible silver leaf and it was about 2GBP delivered) and decided to test it. Silver leaf was mounted on cardboard using double sided tape. Images done with my Monochrome converted Nikon d850m and Rayfact 105mm lens. f11 and ISO400 apart from the 254nm image (which was f11 and ISO6400). Light source was a Hamamatsu LC8 200W xenon lamp, but for the 254nm image I used a 4W UVP filtered lamp. I included a 99% Spectralon diffuse reflectance standard in each image and exposure time was adjusted to keep that as constant as possible for all the images. Images cropped and resized, but no further modifications. Visible - LC8 light and room light, Baader UV/IR cut filter 390nm to 340nm - Thorlabs 10nm bandpass filter, Hamamatsu LC8 Xenon lamp 330nm to 310nm - Edmund Optics 10nm bandpass filter, Hamamatsu LC8 Xenon lamp 300nm - Edmund optics 10nm bandpass filter and Hoya U-340 4mm as the EO filter leaks light above about 600nm, Hamamatsu LC8 Xenon lamp 254nm - Sirchie 253.7nm filter, UVP 4W 254nm lamp Here's the images. The reflectance of the silver leaf does indeed drop sharply at around 320nm. I recorded the RAW files too, and extracted the channel responses for the Spectralon and the silver leaf. Ratioing the silver leaf against the spectralon gave an interesting graph which closely matched the behaviour shared in the original thread (down to 300nm at least). Simple experiment, but took a while to setup. One of the images (the 360nm one) is a bit blurry, which I didn't noticed until I was processing the images. Also some of the dichroic filters show some evidence of light bouncing around between the layers (see the highlights on the 340nm one especially). Am I 100% confident with the 254nm image being 254nm and not leaks? Yes, pretty much as I've tested this filter before, but I suppose being ultra-picky that is the image and data I am least confident with as it doesn't match the published graph.

I've just had a very geeky few days evaluating a Phase One IQ4 Achromatic camera. Medium format BSI sensor (53.4 mm x 40.0 mm), 151Mp, black and white. Thanks to Teamwork Digital Ltd in the UK for making this possible and sending it to me along with an adapter to use my Hasselblad lenses and a really solid tripod. This was one that really interested me, as it should be good for UV as well as visible and IR, and I could try out my Zeiss UV Sonnar on it, as that was made for the Hasselblad 6x6 cameras. First impressions, it is very solidly built, and very well made. Here's a couple of pictures of the camera with some of the lenses I was trying out (El Nikkor 80mm f5.6, and the Zeiss UV Sonnar). Was able to take some images in UV, visible and IR and thought I'd share a few here. Landscape - Chobham Common in the UK in the IR and visible. Natural light in the evening. IR (Zeiss UV Sonnar, Hoya R72) Visible (Zeiss UV Sonnar, Schott S8612 1.5mm plus 420nm long pass) IR (Zeiss UV Sonnar, Hoya R72) Product shot in visible light using a big softbox. Single Bowens GM500 flash. Flower shots (from local flower shop - Tangerine and Green, Englefield Green, UK), in visible and UV. Single Bowens GM500 flash with quartz tube. Sunflower in UV (El Nikkor 80mm f5.6, Baader U) Not sure on this one - Dahlia perhaps - anyway, a white flower in UV and visible. Visible (Schott S8612 1.5mm plus 420nm long pass) UV (Baader U) These images have obviously all been reduced in resolution for sharing. As an example of the resolution of the original images, below is the image of the Sunflower in the UV along with a region marked in red. That little red square is 1000 pixels by 1000 pixels, and this is what it looks like in the original image. Working with the files is certainly challenging for the computer - a full size image in high quality jpeg is around 60Mb and the raw files are pushing 200Mb. You need a lot of storage with a camera like this. Not seen much UV imaging done with medium format, so thought it would be interesting to share. Unfortunately with only 3 days with it, I barely even learned how to use it, but it certainly impressed me in that short time. It has now sadly gone back to the dealer, and if I want to buy one I'll need to get buying those lottery tickets.....

I was able to capture one of our magnolia flowers before they were all gone. They only last two days. Lighting was two 15W germacidal bulbs for all images as was little rushed as the flower significantly darkens over the exposure time. I used the KSS 60mm macro at its f4 setting, which is closer to F8 I think. I white balanced in photoninja and then was surprised that the smallest file size even when 1160x868 is still 1.57MB. So I saved them again in InfranViewer to get the jpegs down to a reasonable size. So you may be missing all the high resolution detail. I captured many of these in the high resolution mode on the EM5mK2 camera. UVA image of flower, I think I used by U330WB80 improved filter for this image: UVB image of flower using the 313bp25 stacked with U330WB80 improved filter: UVC image of flower using 254bp25 filter: I then ripped off the petals you see to open up the inside of the flower. IR using LP 720 filter: Visible UVA with Baader venus U filter: UVB with 313bp25 and U330WB80 improved filter UVB with 303bp filter stacked with U330WB80 and U340 2mm filters ( there is very little 302nm out of my germicial bulb, I am surprised I could boost this up in Photoninja) UVC with 254bp25 filter:

Wilhelmson, U. 2021. Verbascum speciosum Schrad. (Scrophulariaceae). Hungarian Mullein. Flowers photographed in visible, ultraviolet light and a combination of both. https://www.ultravio...garian-mullein/ Verbascum speciosum Schrad. NO: Praktkongslys SE: Praktkungsljus DK: Kandelaber-Kongelys DE: Pracht-Königskerze EN: Hungarian Mullein References: https://www.luontopo...t/showy-mullein http://alienplantsbe...ascum-speciosum https://commons.wiki...ascum_speciosum Comment: A plant native to eastern Europe and western Asia, Verbascum speciosum is known in many other regions as an introduced species and roadside weed. It is a biennial herb forming a rosette of large leaves and an erect stem well exceeding one meter in maximum height. The leaves are 30 to 40 centimeters long and have smooth edges and pointed tips. The plant blooms in a large panicle with many branches lined with flowers. Each flower has a corolla measuring 2 to 3 centimeters wide with five yellow petals. There are five stamens coated in long white hairs at the center. The fruit is a capsule up to 7 millimeters in length containing many seeds. The Hungarian Mullein is the most common Mullein species in Sweden with branched inflorescence. It is characterized by the fact that all stamens are symmetrically attached and that the two lower stamens also have hair on the stamens. Source: http://linnaeus.nrm....ba/verbspe.html Plants collected and photographed in the southern parts of Malmö, Sweden, October 2019, just before the first night frost destroyed the last flowers. All the pictures below show flowers from the same individual. Flower at the collection site: Images below by the same camera and light source: Camera: Canon EOS 60D, EL-Nikkor 80mm f/5.6 old metal type-lens Light source: two UV-converted Godox AD200 flashes with uncoated Quartz tubes Front of the flower, overviews Visible light Filter: Schott BG38, 2mm BUG3-stack image Filter: Schott S8612, 2mm + Schott BG3, 2mm BUG5-stack image Filter: Schott S8612, 2mm + Schott UG5, 1.5mm Ultraviolet Image Filter: Schott S8612, 2mm + Schott UG1, 1mm Front, close-up BUG3-stack image, Filter: Schott S8612, 2mm + Schott BG3, 2mm BUG5-stack image Filter: Schott S8612, 2mm + Schott UG3, 1.5mm Ultraviolet Image Filter: Schott S8612, 2mm + Schott UG1, 1mm Rear of the flower BUG3-stack image Filter: Schott S8612, 2mm + Schott BG3, 2mm BUG5-stack image Filter: Schott S8612, 2mm + Schott UG3, 1.5mm Ultraviolet Image Filter: Schott S8612, 2mm + Schott UG1, 1mm [Published 3 July 2021].

Today we went on lake Como and of course I took a lot of images, in visible and invisible light. I made some TriColours with infrared in the red channel, visible in the green channel and UV in the blue channel. I still have to improve the technique, but the results are not too bad in my opinion. Camera: full-spectrum Canon EOS M Lens: Soligor 35 mm f/3.5 Filters: UV: ZWB2 (2 mm) + Chinese BG39 (2 mm); VIS: Chinese BG39 (2 mm) (only); IR: Hoya R72; All images taken at f/8 and ISO 100. The channels were obtained by converting the whole images to B&W. Except for the second image, all images are the "raw" stacks, no WB applied. I did apply it in Photo Ninja in the second image by clicking the base of the column at the right. Normalizing the exposure times for the visible images, these are the exposures required for UV and IR: UV: ~200-250 VIS (+UV*): 1 IR: 2-2.6 *The BG39 filter used alone passes visible light as well as UV. The resulting image is almost completely VIS-only, but the sky does have a slight violet tint.

Recently got a couple of 75mm filters from ebay that were advertised as BG25 2mm, and BG18 2mm. Longest delivery time ever - I think it was over 3 months from buying them to having them arrive. Given they were cheap, I thought I'd give them a go as they fit in 77mm filter rings. Here's the transmission of the one which was advertised as BG25 2mm. The spectra is sort of what I'd expect for 2mm BG25, although overall transmission is slightly lower than it should be for 2mm, especially in the IR region. Some photos from my garden using the BG25. Images taken on a multispectral EOS 5DSR, using a 17-40mm lens. White balanced in Darktable and reduced in size for sharing. No change in the hue of the image during processing, although contrast has been boosted slightly. The white flowers are Ox-eye daisies (white with yellow centers in the visible spectrum).

EDITs on 17 June 2021. If those of you who are interested would kindly contribute a working description of the terms multispectral image and tricolor image, I would greatly appreciate that. I want to get consensus descriptions nailed down so that we can refine tags, Stickies, tutorials and our general discussions such that everyone understands what we are talking about. Here is what I was thinking, but I am entirely open to changing my own thoughts about these descriptions. In my descriptions I am making the assumption that everyone knows what is an RGB channel stack !!! DESCRIPTION A Tricolor Image is an RGB channel stack of 3 images where each image is made from a different sub-region within one of the following broad intervals. Typically three narrowband filters are used to photograph the subject. Ideally, the narrowband filters do not overlap or overlap very little. Ultraviolet [10-400 nm] Visible [400-700 nm] Infrared [700-104 nm] The Tricolor goal is to assign visible colors to photos made with "invisible" wavelengths. The selection of sub-regions may of course be restricted to smaller intervals within these larger categories. Tricolor Example: Red [300-320 nm] + Green [330-350nm] + Blue [360-380 nm] where each filter is a narrow 20 nm UV-bandpass. DESCRIPTION A Multispectral Image is typically thought of as an RGB channel stack of 3 images - UV, Visible and IR -where each image is made within the following broad intervals using either a broadband or narrowband filter. Other combinations can also be considered multispectral such as the UV, Vis and Vis example below. Ultraviolet [10-400 nm] Visible [400-700 nm] Infrared [700-104 nm] The Multispectral goal is to produce an image which might represent the outcome of photographing a subject in mixed light or to make an image which emulates the way an animal or insect might see. Multispectral Examples: Red-UV + Green-Vis + Blue-IR where each image is made under a broadband filter such as the BaaderU or an RG780. Red (entire UV image) + Blue (Visible Green Channel) + Green (Visible Blue Channel) Mix it up and see what happens. The 7 Electromagnetic Wavebands: Nobody can quite agree on the endpoints, so please don't let this bother you. This is not Science Class. There won't be a pop quiz. For example, Wikipedia likes to start Infrared at 750 nm. But any UV/IR photographer would start it at 700 nm because wavelengths in 700-750 nm contaminate Visible (and UV) photos. Gamma Rays X-Rays Ultraviolet [10-400 nm] Visible [400-700 nm] Infrared [700-104 nm] Microwaves Radio Some Sub-Wavebands: Same warning - don't sweat the endpoints. This is just a bit of guidance for general discussion. Near UV.........[300-400 nm] Middle UV......[200-300 nm] Far UV............[122-200] Extreme UV....[10-121 nm] UV-A.....[315-400 nm] UV-B.....[280-315 nm] UV-C.....[100-280 nm] Near IR (NIR)...........................[700-1400 nm] For the typical reflected IR photographer I think we would use 800-1100 nm. Shortwave IR (SWIR)..............[1400-3000 nm] Mid-wavelength IR (MWIR).....[3000-8000 nm] Longwave IR (LWIR)................[8000-15000 nm] NOTES: 1) Neither Tricolor nor Multispectral imagery is new. It's been done since the film (both still and movie) days. It is definitely much easier to make such images these days using digital files. 2) Yes, certain single dual bandpass filters or really wide filters might produce results which could be considered either Tricolor or Multispectral. Some light from such a filter is likely going to "contaminate" some other light, so the result may vary from what can be obtained with an RGB stack. Besides which, where's the fun?

Finally, after years of having my filters attached to a cardboard/tape roll, I mounted them in appropriate filter rings. This improves versatility a lot. I took a UV, VIS and IR image of a plant to test multispectral stacks. The filter rings allow me to change my filters without moving my camera (at least, reducing the forces on the lens). I didn't refocus, and I didn't align the images, so enjoy some chromatic aberration. The paper tissue was used as a white balance target. UV, VIS and IR images white balanced in-camera, stacks white balanced in Photo Ninja (it provides better results than IrfanView). This time I worked with .tif files, so the quality should be better. Camera: full-spectrum Canon EOS M; Lens: Soligor 35 mm f/3.5. Filters: UV: ZWB2 (2 mm) + Chinese BG39 (2 mm); VIS: Chinese BG39 (2 mm); IR: Hoya R72. UV (f/8, ISO 100, 8 s exposure): VIS (f/8, ISO 100, 1/125 s exposure): IR (f/8, ISO 100, 1/60 s exposure): TriColour (IR = red, VIS = green, UV = blue): IRG: GBU: Notes: - My Chinese BG39 is not the best filter to cut UV/IR, because it doesn't cut UV at all (at least, most UV) and it suppresses the reds too much. But this is what I have at the moment. - IRG and GBU should be quite known abbreviations here, but to recap: An IRG image has infrared in the red channel, red in the green channel and green in the blue channel; A GBU image has green in the red channel, blue in the green channel and UV in the blue channel.

We had a rainbow today, and I had to try some invisible light photography on it. My camera caught some drops of water, but nothing to worry about. Cameras: Samsung Galaxy A40, front camera (visible); Full-spectrum Canon EOS M (UV, IR, full-spectrum); Lens: Soligor 35 mm f/3.5. Filters: UV: ZWB2 (2 mm) + Chinese BG39 (2 mm); IR: Hoya R72; No filters for the full-spectrum image. Visible light (f/1.7, ISO 40, 1/2370 s exposure). Image cropped to approximately match the others: Infrared (f/8, ISO 100, 1/250 s exposure): Ultraviolet (f/8, ISO 100, 1 s exposure): I have an image with more exposure, but the rainbow is less visible. Full-spectrum (f/8, ISO 100, 1/1000 s exposure): The camera is very sensitive in full-spectrum. If I had the lens wide open, I would have overexposed at ISO 100. Also, the lens has quite a bit of chromatic aberration with a band this wide.