Andy Perrin Posted February 8, 2017 Share Posted February 8, 2017 I wanted to try out the IRG photos, and I lucked out with this lime, which looks striking in IRG. halogen, Asahi Super-Takumar 50mm/1.4, NEX-7 body Visible photo, using 1.75mm S8612, F11 1/30" ISO100 NIR photo, using Hoya R72, F11 1/200" ISO100 IRG from the above images, with a re-white balance off the stove top: Link to comment
Adrian Posted February 9, 2017 Share Posted February 9, 2017 Apologies, I must have missed something...IRG ? Link to comment
Guest Posted February 9, 2017 Share Posted February 9, 2017 I like the crisp results from the IRG version. I also shot a lime recently, in a multispectral set (image below). While limes, like other fruits, look rather unappetizing under UV, their fluorescence is quite colorful (though I wouldn't exactly say that looks appetizing either!). On the outer skin, I wonder whether the dark spots are dark because they are IR transparent (thus dark because of shadowing in pits/holes) or IR absorptive. If its something absorptive I wonder whether that would indicate emission somewhere else on the EMS, perhaps even further up into IR? If I was rich I'd buy a SWIR camera and start adding a fifth shot to my multispectral sets ;). Just to be clear - are your "IRG" images a composite of IR in the red channel, Red in the green channel, and Green in the blue channel? Here's my multispectral lime: Link to comment
Andy Perrin Posted February 9, 2017 Author Share Posted February 9, 2017 Apologies, I must have missed something...IRG ? Just to be clear - are your "IRG" images a composite of IR in the red channel, Red in the green channel, and Green in the blue channel?Yes, that's right. I took the IR from the Hoya R72 and did "desaturate" in Photoshop, then I made a new document with the desaturated IR in the red, Red in the green, and Green in the blue. After that I did a one click white balance in PhotoNinja on the stove top. Link to comment
Andy Perrin Posted February 9, 2017 Author Share Posted February 9, 2017 I also did a UV using my Tuofeng torch, which is fairly narrowband around 365nm. Saturation is increased a lot to try to deal with that. 2mm "UG11" (there are some doubts about whether this is a Chinese glass or not), 1.75mm S8612, Noflexar lensF8 30" ISO100 And finally, my SWIR (shortwave infrared, 1480nm-1600nm) photo, using the halogen light source, the Edixa Auto Cassaron lens, a Thorlabs SWIR long pass filter that blocks both visible light AND near infrared out to 1200nm, and a fluorescent screen that has the following manufacturer-supplied absorption spectrum: Link to comment
Guest Posted February 9, 2017 Share Posted February 9, 2017 Andy, how was your SWIR image photographed? My understanding is that CMOS and CCD image sensors are photo blind above 1200 nM. Link to comment
Andy Perrin Posted February 9, 2017 Author Share Posted February 9, 2017 Andy, how was your SWIR image photographed? My understanding is that CMOS and CCD image sensors are photo blind above 1200 nM. You are correct. The cutoff is actually closer to 1125nm. So the SWIR is photographed using a fluorescent screen that upconverts SWIR photons into NIR photons. Physically, it is the anti-Stokes effect. (I believe this to be the cheapest SWIR camera setup in existence! ...and it was still too damn expensive. :( ) Link to comment
Hornblende Posted February 10, 2017 Share Posted February 10, 2017 Interesting how the wood takes a nice red tone in the IRG picture. (I believe this to be the cheapest SWIR camera setup in existence! ...and it was still too damn expensive. :( )Is it even possible to possess a dedicated SWIR camera? I heard it is only reserved for military application in the US. EDIT: I was wrong, these cameras are also commonly used in research... Link to comment
Andy Perrin Posted February 10, 2017 Author Share Posted February 10, 2017 Yes, you can buy one, but even on ebay the cheapest I could find is about $9000. This setup (not counting camera body) is <$500. They are used extensively to examine the underdrawings of paintings, too! Lots of museums have them. I have created a new thread for the SWIR stuff. Please reply there. Link to comment
Andrea B. Posted February 10, 2017 Share Posted February 10, 2017 I do like that IRG look !! :D Link to comment
OlDoinyo Posted February 13, 2017 Share Posted February 13, 2017 Anti-Stokes fluorescence is rather inefficient, is it not? How dim are these images? Link to comment
Andy Perrin Posted February 13, 2017 Author Share Posted February 13, 2017 Dim! 8" at ISO1600 and F2 or so, and a 600W quartz tungsten halogen lamp at close range. The lime was rather dry by the time I finished! Link to comment
OlDoinyo Posted February 13, 2017 Share Posted February 13, 2017 Dim! 8" at ISO1600 and F2 or so, and a 600W quartz tungsten halogen lamp at close range. The lime was rather dry by the time I finished! My experience with such light sources is that they tend to ignite the subject matter! Surely art conservators could not use them on high-value pieces, and incandescence from heated subjects could be a contamination problem. Link to comment
Andy Perrin Posted February 13, 2017 Author Share Posted February 13, 2017 HEEE, no, art conservators don't use my LOW COST SWIR setup. If I had $15,000 ($9000 used on ebay), I could buy a new InGaAs camera, or a germanium one, both of which can cover SWIR with a great deal more sensitivity and with no flames. :-P The quality is so much better -- someone here posted a photo using a TriWave:http://www.ultraviol...ndpost__p__2288 Compare to my self-portrait, taken in sunshine (my ability to focus has improved since taking this, but you get the idea): Link to comment
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