Search the Community

EDITOR'S NOTE: The other thread had gotten long enough. Some good things were learned there! I have some additional work with these filter stacks to post so we can continue to discuss the "ideal" bee vision filter stack. Of course, I doubt there is an ideal filter stack for this kind of work, but we will enjoy talking about it. :) Discussion: UG5 + IR-Cut Filter Stack, Part 1 I made some UvGB photos of a red Gerbera Daisy using my Hoya U-330 UV-pass filter stacked with different S8612 IR-blockers. Some little breezes were encouraging the flowers to dance, so I stayed at f/8 instead of my usual f/11. The filter stack which worked best to block red in the UvGB photographs was the Hoya U-330 stacked with two S8612 IR-Blockers, 1.75 mm and 2.0 mm in thickness. Shots were made of white reflective standards and a CC Passport in order to create visible, UV and UvGB colour profiles in Photo Ninja. Some of that is lost after resizing and embedding an sRGB profile for online display. Equipment: D600-BB + UV-Nikkor 105/4.5 + Sunlight Visible Reference[ f/8 for 1/10" @ ISO-400 with Baader-UVIR Cut Filter ] UV Reference[ f/8 for 1.3" @ ISO-200 with BaaderU UV-Pass Filter ] Equivalent to f/8 for 1/1.6" @ ISO-400. UvGB[ f/8 for 1/10" @ ISO-400 with Hoya U-330 UV-Pass (1.5 mm) + S8612 IR-Block (1.75 mm)] UvGB[ f/8 for 1/10" @ ISO-400 with Hoya U-330 UV-Pass (1.5 mm) + S8612 IR-Block (2.0 mm)] UvGB[ f/8 for 1/10" @ ISO-400 with Hoya U-330 UV-Pass (1.5 mm) + S8612 (1.75mm) + S8612 IR-Block (2.0 mm)] Two S8612 filters.

Dear All I am new to this topic, but I find it extremely fascinating. I have Canon Cameras 760D,500D and a converted full spectrum 500D My Main aim is to learn from everyone and share what I find out. I like experimenting with IR filters, 720 and 850 and also the UV filter from BG I use both 500D's *converted and Normal( with filters to create pictures and I am always amazed by the outcome. I have attached 2 examples first one with converted camera of the Taj Mahal and the second one from the unconverted using just filters of a Hunters Seat in Germany, where I live. I look forward to learning :-) Cheers griff

In the news today, Hidden figure in Leonardo da Vinci notebook revealed Nice animated image of what appears to be some 20+ spectral bands.

I was checking on recent publications by Adrian Dyer's group and I came across this: Garcia et al 2015 http://journals.plos...al.pone.0125817 Make your self a cup of coffee, or something stronger before you start it as it will make your head hurt. It compares, in the visible region only, a normal DSLR with a multispectral camera with 128 channels. I have no idea how much that costs or whether it would work for UV but it might solve my never ending question of what our false UV colours mean and if they really do relate to wavelength or are just clever artifacts of the RGB dyes and the white balancing process. Cheers, Dave

It should also be pointed out that a UG-5 + IR-cut stack is technically a simulation of tetrachromatic vision (UV + blue, green, and red), and not UV + blue-green. Some red does get through in that stack. Whereas, our current scientific understanding is that bees are not true tetrachromatics, because their ability to detect red-wavelength light is highly muted or limited. Instead, I would say that "bee vision" is "color-shifted" (towards the end of higher energy), so that they see predominantly in UV + blue/green (and an increasingly muted perception of color as the wavelengths head further towards the red-end, so that yellows are still visible, oranges are decreasing in saturation, and red is almost non-existent to them). Thus, bees mostly remain trichromatic animals, just like humans ... just color-shifted more towards the violet-blue side. On the other hand, it is "butterfly vision" that is assumed to be true tetrachromatic vision (as well as certain species of birds). However, I am aware that this still remains an area of great contention, because our current understanding of the "color interpretation" of other animals is based upon what wavelengths their eyes can detect, but it's still up to conjecture as to how their brains actually assign (or map) these colors. Meaning, just because we know what wavelengths an animals eyes can detect, doesn't mean we can predict with any certainty how their brains will interpret the actual wavelength in terms of assigning a "color" to any given wavelength. Which is why the better way to state such photography is to add the word "simulated" to the description. (Ex: simulated bee vision, simulated butterfly vision, and so on.) Anyway, the bottom line though is that UG-5 + an IR-cut stack is not "bee vision", because it produces a tetrachromatic result, and not just UV + blue-green. (There is red in there, too, and some red-colored flower parts will show up in the image as red if the white-balance is neutrally-distributed). I used to go along with this inaccuracy for a while, too (excluding the red in the description), until my own exploration of such stacks taught me better (when I started seeing reds showing up in such stacks). Thus, to produce a "simulated bee vision" result with a UG-5 + IR-cut stack, I would de-saturate the red-end results, or even consider bringing any reds close to a grey-scale appearance.

EDITOR'S NOTE: I split Alex' question from the thread it was posted in so that we could pursue it in more detail. To review, a "channel stack", for our purposes, is basically a 3-layered (R-channel, G-channel, B-channel) difference set where different wavelengths of light are placed in separate channels. There is more than one technique for making a channel stack depending on which editor or tools are used. Here we are concerned with making channel stacks which combine UV and Visible layers. For example, Bee Vision can be simulated with a channel stack made up of UV, green and blue layers where the UV is placed into the Red channel. To set the stage, I had shown a channel stack for a flower foto made up of the UV red channel and the visible blue and visible green channels. *********************************************************************************************************** Andrea, why do you split UV shot into three channels? Shouldn't it be just treated as equivalent of one channel for composing? E.g., just converted to monochromatic?

The GBU-->RGB cross-sampled image is the rarer counterpart of the better-known IRG image, and unlike the latter, has no practical history or technical application; it is largely a curiosity. No film ever produced this sort of image. The only way to obtain this type of image is by a two-exposure technique. My only previous forays in this direction have been on sunny days; but the other day was quite foggy and I was curious to see how this genre interacts with such conditions. I like to shoot in the fog, anyway; give me trees and give me fog and I can usually come up with something, and the best of what I came up with on this occasion follows. Here are some things you might find interesting to look for: -Vegetation is rendered in hues ranging from maroon to rust-brown. -Objects take on a greenish-yellow cast as they become more obscured by the fog. I am not completely sure if this is an artifact of workup or if this reflects some underlying physical reality such as differential Rayleigh scattering or absorption by water (which has a transmission maximum around 466 nm). I have suppressed the effect in several frames where it seemed excessive, but otherwise left it largely alone. I have rendered the fog colorless; it could be argued that this is an artifice, as the ambient UV flux is in reality much less than either the green or blue flux. However, I did not want strongly tinted images. -Yellow: This denotes surfaces which are UV-dark while reflecting visible. Lichens, apple blossoms, and titanium dioxide paint show yellow. -Magenta: this appears on strongly blue-absorbing surfaces that are UV-bright. To my surprise, it shows up in the foreground of one of the frames. All images obtained with Sony A900 and Steinheil 50mm lens at various apertures (aperture matched between frames of same shot.) UV component obtained through Baader U2 filter with manual exposure and custom white balance. Visible component obtained through KolariVision deconverting filter with aperture-priority automatic exposure and +.3 to +.7 exposure compensation. and "cloudy" white balance. "The Bashful Bush 1" "The Bashful Bush 2" "Outcrop" "False Autumn" "Among Strange Flowers" "Triple Echo" "Apple Blossom Time" "Rake and Sand Trap" "Right, Left, Right" "A Choice of Uncertainties" GBU images often do not have the in-your-face surreality of some other cross-sampled image genres; some of these images might be mistaken for ordinary color images. In every case, however, the scene as depicted does depart substantially from what the naked eye saw (or the visible source frames, for that matter.) Green grass is transformed into a quasi-autumnal brown, for example.

Schmitt, K. D. (2015) Tulipa saxatilis Sieber ex Spreng. (Liliaceae) (Cretan Rock Tulip) with crab spider. Flower photographed in ultraviolet and visible light and simulated bee vision. http://www.ultraviol...lip-and-spider/ Hermannshof Park, Weinheim, Germany April 2015 Wild form or Cultivar (?) Synonym: Rock Tulip Reference: 1. Cretan Flora (2015) An Illustrated Guide to the Flowers of Crete. Tulipa saxatilis. http://www.cretanflo..._saxatilis.html Comment: This small tulip is endemic to the rocky fields of Crete and other Greek Islands. It is has also been cultivated and naturalizes easily. The spider is just enjoying some lunch. In UV the Cretan Rock Tulip is absorbing with a darker center around the stamens. Equipment [Panasonic GH2 broadband + Cerco 94mm Quartz Fluorite Lens] Left: Visible Light image (UV/IR Cut filter) Middle: UV Image (Baader-U Filter) Right: Simulated Bee Vision Image (XBV4 Filter - proprietary) http://m9.i.pbase.com/g9/08/747708/2/159824949.mYzpy8wD.jpg EDITOR'S NOTE 27 Mar 2021: This image will no longer load from pbase.

This is a fun little lens. Two renditions. This is Vis + IR. I'm sure no UV made it in there. ADDED LATER: After those finally managed to load up, I decided I didn't like them after all. So here are two more renditions of a similar scene. This is how much colour is in the filterless shot if you reset the "black point". And another experiment. This one I think I like best. Those autumn leaves dotting the grass. The curve of the path. The skewed perspective. (Adds 'creative tension', lol.)

Until last Friday, the spring has not fully came into my part of the world, and the only actively blooming flovers are the Winter Aconite, with a nice patch just next to the entrance to my work. So I have been experimenting with some post-processing.

For the past half-decade or so I've had the great pleasure of working with Ken Boydston and Richard Chang of Megavision to help them develop a lens for their multi-spectral imaging system. This is used mainly by museums to document and archive early books and documents. The general term for this is "Cultural Heritage Imaging", and its an amazingly interesting field. Although I'm not actively involved in any of the exciting imaging projects using the Megavision system (I'm just a lens supplier), I do get to hear about some incredible projects from time to time. One example is the photographic analysis of David Livingstone's diary, which has been fading in storage for the last century and a half. Apparently he made ink out of berries, which hasn't held up well. Fortunately, through multispectral photography it is possible to restore documents like this to legibility. As Ken recently wrote to me, "PBS is airing a National Geographic special on the rediscovery of the diaries and the technology employed that brought them back to life. We are delighted to have been a part of this fascinating project." Showtime will be next Wednesday, 26 March (check for local times http://www.pbs.org/w...s-episode/1103/)

Blum, A.G. (2013) Cucurbita cf. pepo L. (Cucurbitaceae) Ornamental Gourd. Gourd photographed in ultraviolet, visible and infrared light. Channel stacks. http://www.ultraviol...namental-gourd/ Middletown, New Jersey, USA 12 November 2008 Purchased at grocery store Comment: This pretty orange Gourd made a nice still life subject. In UV the irregular growth flaws and various scrapes from handling are more obvious although some of that still shows up in the IR photo. Reference: 1. The American Gourd Society (2014) This is a nonprofit organization dedicated to the education and instruction of those persons who are interested in the culture, uses, history, and/or crafting of gourds. Equipment [Nikon D200-broadband + Novoflex 35mm f/3.5 Noflexar] Visible Light [f/11 for 1/180" @ ISO 400 in Sunlight with Baader UVIR-Block Filter] Click, then click again to see the largest version. Ultraviolet Light [f/11 for 4" @ ISO 400 in Sunlight with Baader UV-Pass Filter] Shooting UV with my old D200-broadband could really bring out the noise. That combined with resizing has induced a few artifacts. Click, then click again to see the largest version. Infrared Light [f/11 for 1/125" @ ISO 400 in Sunlight with B+W 092 IR-Pass Filter] Click, then click again to see the largest version. Composite The preceding Visible, UV and IR frames were stacked as difference layers in Photoshop. Making a composite like this does not always reveal anything particularly unusual. It's just fun to do. The layers do not match up perfectly, so you can detect a few edge discontinuities in the full-sized version. Multispectral Channel Stack [uV->Purple, Visible->GreenBlue, IR->Orange] Each frame was assigned to a colour channel. Typically this is done via an RGB channel assignment. I sometimes like to use Purple (128,0,255), GreenBlue(0,255,128) and Orange(255,128,0) instead. Again, such a composite may not be particularly meaningful, but the result is pretty. Multispectral Channel Stack This is the preceding stack with a 45° turn of the colour wheel. The gourd is starting to look like an apple! Colorized Triptych I put the Visible frame as a Color layer over the UV frame and then the IR frame in order to "colorize" them. The three photos were then combined in this triptych. The forum software's auto-resizing has clobbered the result a bit, but you can still get the general idea. From left to right, the UV, the Visible and the IR frame, respectively. .

As a precursor to using UV for landscape photography, it can be useful to look into the various spectral bands available to invisible spectrum usage. One can combine bands to make false-colour, multispectral composites. There are virtually endless combinations to explore. Here are a few early experiments on an alpine landscape at Jotunheimen Norway. Taken with a broad spectrum modified D1 and the Nikkor 28 mm f/3.5 lens. This lens is usually regarded as excellent for IR photography, but its UV propertiers are less familiar. While it certainly does not transmit deep into UV, it can depict the usual test objects such as UV patterns of a dandelion in a satisfactory manner. For this hastily improvised trial I used a combination of UV and two IR bands. I had no suitable bandpass filter for visible at hand on that trip. All captures were conducted at f/16. The mountain air was crystal clear and cool to give little turbulence and excellent visibility even of the remote peaks (up to 15 km away). First autumn colours had started to appear (this was mid August, 2004). UV light: Hoya U-360 stacked with B+W BG-38. The ground vegetation is rendered fairly dark and the sky is bright. Water surfaces reflect sky and thus are rendered rather bright as well. There probably is some IR contamination present in this capture due to the non-optimal filtration, but the expected UV appearance is present. IR band 1: Hoya RT-830 filter, with a peak around 830 nm and having fairly strong attenuation to either side of the peak. This represents the middle section of the near photoactinic IR. As expected, vegetation is bright and sky and water show up quite dark. IR band 2: Hoya RG1000 filter, starts to transmit around 950 nm and is fully transmitting above 1000 nm. The IR character of the landscape is very strong. Sky and water surfaces are jet black, while vegetation is medium grey to bright depending on vegetation type and ground moisture. When these three are combined into a false-colour composite, or multispectral image, the following picture results: Image reference: :ALPINE_T04081397513_MS(UV,IR).jpg Here, UV is coded B(blue), IR 1 is G (green) and IR 2 is R (red). In the composite, the haziness brought by the UV band tends to blur the distant mountain peaks.