colinbm Posted December 14, 2013 Share Posted December 14, 2013 Another Allamanda flower with a Violet Blue Cyan Green filter about 380nm to 530nm. For those interested, I have uploaded this file .X3F to DropBox, it is free. It is about 10mb.https://www.dropbox....20380-530nm.X3F It is a Sigma .x3f file from a Sigma DP1 compact camera. Because it is an original (older) Sigma compact some propriety photo editor programs will open it, BUT it is best to open it with the Sigma Photo Pro RAW converter, convert it to a .tiff file & work it that way. I am a novice at PP & only use Sigma Photo Pro, I have next to no experience with the other editors.Windows & Mac versions.....http://www.sigma-dp1.com/software/spp/ Straight out of Sigma DP1 full spectrum camera, with about a 380-530nm filter .JPGThis is a astro 1.25inch filter so it is a circle on the sensor.Please excuse my hairy arms & legs, it is high summer in Queensland :) Good luck & please share your results.CheersCol Link to comment
Andrea B. Posted December 14, 2013 Share Posted December 14, 2013 Col - The link seems to be for the previous photo and not this new one. Who makes this filter ? Link to comment
colinbm Posted December 14, 2013 Author Share Posted December 14, 2013 Sorry about the link........I have replaced it & it seems OK now.The filter was from Omega Optics, a 25mm off eBay :DCheersCol PS I could start some discussion & suggest that this maybe close to Bee vision ??Col Link to comment
Andrea B. Posted December 15, 2013 Share Posted December 15, 2013 Well, Col, I don't know about the bee vision thing. Given bees' trichromatic vision with peaks at UV/345nm, B/440nm and G/535nm, which part of that photo would you assign to UV ? Link to comment
colinbm Posted December 15, 2013 Author Share Posted December 15, 2013 Thanks AndreaThe sub 400nm part that is reflecting UV light ?The UV signatures in the flower are present ?CheersCol Link to comment
Andrea B. Posted December 15, 2013 Share Posted December 15, 2013 From the reference below (and others), we know that a flower which is visibly yellow-ish and also UV-reflective, such as your Allamanda on its petals, is seen by the Bee as a nameless colour designated as "UV-green". How that might be represented in fotos is open to discussion. There seem to be many interpretations of "Bee Vision". Look at some of Nico's work here on UVP, for example. UV-reflective, visible red flowers are seen by the Bee as a nameless colour designated "UV". I don't think you have that in your foto. Chittka, L., Shmida, A., Troje, N., & Menzel, R. (1994) Ultraviolet as a component of flower reflections, and the colour perception of Hymenoptera. Vision Research, 34, 1489-1508. Link to comment
colinbm Posted December 16, 2013 Author Share Posted December 16, 2013 Thanks for these references Andrea, I am learning.How does a Bee see a peak of 345nm when the intensity that reaches Earth is so low. How would the acute brightness of the green affect the Bee's vision ?CheersCol Link to comment
Andrea B. Posted December 16, 2013 Share Posted December 16, 2013 I don't know that much about it, Col. :DApparently bees see green foliage as "uncoloured". I suppose that means some equivalent of grey. Link to comment
colinbm Posted December 16, 2013 Author Share Posted December 16, 2013 Thanks AndreaSomewhere very recently I read that the long waves dominate the short waves, as in full spectrum photography, small amounts of IR will dominate large amounts of UV.So in this image of mine here, UV to Green filter, yellow is trying to show but green is nowhere to be seen & the UV / Blue is dominating the image.Do you have any opinion here please ?CheersCol Link to comment
Andrea B. Posted December 16, 2013 Share Posted December 16, 2013 Do you have a transmission chart for this filter?Without a transmission chart or a further test there is no way to tell whether IR is contaminating the photo.Or how much very-near-UV might pass. :D To test whether your filter leaks IR, stack it with an IR-pass filter which cuts in past 700nm. If shooting with an IR-leaky UV-pass filter such as the Hoya 340 or Hoya 360, then IR will contaminate the UV photo because there is simply so much more IR in Sunlight than there is UV. Even minor IR leaks in a UV filter can cause some contamination. So, it is not that longwave light "dominates" shortwave light because of wavelength, it is rather that there tends to be more longwave light present in the ambient natural lighting of a given scene. And much less shortwave light. If you are asking whether the Allamanda green leaves should appear green in this photo, I don't know. Many green leaves reflect a large blue component also. And, surprisingly, some red sometimes too. Mix those possibilities together with the leaves' reflectivity (or absorption) in UV, and who's to say what the appearance of the Allamanda green leaves will be with this particular filter? Note that there is no uniformity in appearance of green foliage in UV. Some goes dark, some goes light, some goes grey in UV photographs. Also, again, without a transmission chart to see what the right-hand shoulder looks like in terms of slope and cut-off, I wouldn't be able to say how much green you should expect here. Another thought here - when shooting with this 380-530nm filter, you have to choose an in-camera white balance. That can very well affect what you are seeing in the photograph. Without some kind of reflective standard to calibrate the WB response (either in-camera or later in an editor), we don't have a way to know what the proper colour balance should be for this filter. All good questions, Col. Hope I've helped with some aspects of this. Keep experimenting ! Link to comment
Andrea B. Posted December 16, 2013 Share Posted December 16, 2013 After writing the preceding, I got to wondering if there are colour standards available which are stable under UV or IR light. And, it reminded me, that perhaps you might want to look for a piece of white Teflon to use as a reflective standard ? White Teflon is a fairly good substitute for an actual reflective standard. It is not always diffuse, but works pretty well for colour balancing with relatively minor fall off in the UVIR. Teflon = PTFE = poly-tetra-fluoro-ethylene.I don't know where it can be purchased. You will have to Google around. Link to comment
colinbm Posted December 16, 2013 Author Share Posted December 16, 2013 Thanks AndreaI have been looking for some PTFE to make a reflective standard / WB target, will look again after Christmas.I have a grey card that I use for full spectrum WB. The Sigma Foveon cameras are difficult to get custom WB with different filters. The particular grey card that I use is the only grey card that I have found to give a reliable WB on in full spectrum and it can be tweaked in the Sigma Photo Pro raw converter. I have also found that Incandescent WB works well in sunlight for UV imaging as it gives a blue shift to the image.This is the filter that I used for this image at the top of the thread http://cgi.ebay.com....ME:L:OU:AU:1123I used a Tiffen Standard Hot Mirror with this filter as it passes the UV end and cuts the IR end. So I thought !Ok I placed a IR720 filter over the UV-Green filter and I got a lovely IR image !I then placed the Tiffen Standard Hot Mirror over both these filters and got a dark IR image, still not good !I then placed the Sigma Hot Mirror over the IR720 and UV-Green filters and got a black image ;)So the moral of the story is the UV-Green filter leaks IR as the graph shows, but the Tiffen Hot Mirror doesn't do the job well enough either :(So check and double check and check again :DCheersCol Link to comment
Andrea B. Posted December 17, 2013 Share Posted December 17, 2013 Col, if you look in our Filter Sticky you can find some info about IR blocking filters and glass.Probably the best IR-blocking to use with a UV filter is some BG39 or S8612 glass. It can be purchased mounted. Either of these would also work over your 380-530 filter to block IR.The Tiffen hot mirror is not a good choice as you have discovered. Filter Sticky: http://www.ultravioletphotography.com/content/index.php?/topic/140-ultraviolet-photography-2013-filters/ Some experiments with B39 and S8612 to block IR leak in UV-Pass filters.http://www.ultravioletphotography.com/content/index.php?/topic/480-uv-pass-filter-test-i-baader-u-precision-uold-hoya-340-s8612-hoya-360-s8612/http://www.ultravioletphotography.com/content/index.php?/topic/477-uv-pass-filter-test-ii-bw-403-s8612-bw-403-bg39-precision-uold-baader-u/ Link to comment
colinbm Posted December 18, 2013 Author Share Posted December 18, 2013 Thanks AndreaI am learning fast :DI am now on the lookout for a S8612, it will be interesting to see how much IR it blocks.I'll try & leave you in peace for Christmas so you can enjoy it.I'll be waiting to see what Santa brings me & what the New Year brings too.Happy ChristmasCheersCol Link to comment
colinbm Posted December 18, 2013 Author Share Posted December 18, 2013 The MaxMax X-Nite CC1 is showing IR with the IR720 & UV-Green filters......I also had a look through the B+W 486 & 489 filters through the IR720 and UV-Green filters and got IR images from both on the Sigma DP1 camera !!The B+W 486 was only slightly darker IR then the B+W489. I hope the S8612 really blocks IR above 700nm on my Sigma cameras ? Because the Sigma Hot Mirror (420-660nm) is the only ICF that I have that cuts IR......but cuts UV too :DScheinder also has "Transmission range of IF UI 515 is from 380 nm to 650 nm". http://www.schneider...-ir-cut-filter/But it still has tiny bumps in near IR like the 486 & 489 !Col Link to comment
Andrea B. Posted December 18, 2013 Share Posted December 18, 2013 Well, blocking IR is a tricky business as you have already discovered. :D What you want to do is look at transmission charts and try to pick an IR-blockerwhich blocks where your filter leaks and leaks where your filter blocks. If that made sense !?!?None of the BG glass or the 8612 cuts off precisely at 700nm.So matching up transmission charts is a must. I've made good UV fotos with very IR-leaky UV-pass filters stacked with a BG39 or S8612 of sufficient thickness.However, stacking has its own potential problems - possible flare or slower exposures. I don't think I would choose a filter which cuts off UV at 380nm however.That's not much UV getting through. ****** You seem to have a lot of UV-pass filters ? Do you have the Baader-U ?? Link to comment
colinbm Posted December 18, 2013 Author Share Posted December 18, 2013 Thanks again AndreaYes I have a variety of UV & IR cut & pass filters, but not the Baader-U yet. When I get the cover glass on a Sigma dSLR replaced with quartz, I will look at getting a Baader-U. Then I'll have to get a suitable lens too :DI have just been shown this Kolari Vision hot mirror, seems too good to be true ?? http://www.kolarivis.../hotmirror.htmlCheersCol Link to comment
Andrea B. Posted December 19, 2013 Share Posted December 19, 2013 Given that Kolari says it is an absorbtion filter, I'd say it is likely to be made from one of the newer Schott BG 60/61/62/63/64 types of filter glass. LINK: http://www.schott.co...lass/index.html Schott is also making a new VG20 IR blocker.LINK: http://www.schott.com/newsfiles/20131120124112_151_2013_schott_vg20-filterglas-fuer-medizintechnik_en_final.pdf Link to comment
colinbm Posted December 19, 2013 Author Share Posted December 19, 2013 Thanks very much AndreaThese filters look interesting...I don't know how to read these Schott's transmittance charts, the bottom lines have figures like '1E-08' ?Also the chart of interest https://www.schott-pictures.net/pictures/download/199270?presskit_id=217227 has cut-off 565nm, where it looks more like 700nm to me ??CheersCol Link to comment
Alaun Posted December 19, 2013 Share Posted December 19, 2013 Well, Colin, 1E-08 stands for 0.00000001 that is a very smal number compared to 1 The Schott filter chart is given in a logarithmic scale on the y-achsis The cut off frequency/wavelength is where you have only 50% transmission left In the given chart you have about 100% at about 1 (close to the top of the chart, 1 represents 100% here) You have a fall off down to 50% (that is about 0.5 on the y-achsis of that chart) at 565 nm At 700nm there is almost nothing left (about 0.01%) Cheers Link to comment
colinbm Posted December 20, 2013 Author Share Posted December 20, 2013 Thanks Werner for explaining that so well......so the first horizontal line down is 0.1.CheersCol Link to comment
colinbm Posted December 20, 2013 Author Share Posted December 20, 2013 Thanks WernerSo the first line down from the top is 0.1 or 10%. 0.5 will be higher then half way.CheersCol Link to comment
colinbm Posted December 21, 2013 Author Share Posted December 21, 2013 Thanks AndreaLooks good.CheersCol Link to comment
Andrea B. Posted December 21, 2013 Share Posted December 21, 2013 They really squished down the left-hand scale between 10% to 100%. I suppose they wanted to emphasize how much the near-IR was being cut. Link to comment
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