Andrea B. Posted February 10, 2015 Share Posted February 10, 2015 Blum, A.G. (2015) Saintpaulia sp. H. Wendl. (Gesneriaceae) African Violet. Flowers photographed in ultraviolet and visible light. http://www.ultraviol...et-iridescence/ Comment:The petals of this African violet provide the best examples of conical cell iridescence I've photographed thus far. There is real colour change based on the directionality of the light. So I have posted more than the usual number of examples to illustrate this. Set 1Middletown, New Jersey, USA07 February 2015Cultivar from garden store Equipment [Nikon D600-broadband + Rodenstock 50mm f/3.5 Omegaron]The EXIF data in the photographs is incorrect for the lens focal length and lens speed because this lens is unchipped. Visible Light [f/11 for 1.3" @ ISO-100 in Sunlight with Baader UVIR-Block Filter]Photo may be clicked up to 1000 pixels wide. Unresized extract from preceding photo, anthers. Ultraviolet Light [f/11 for 1/1.6" @ ISO-400 with Nichia 365nm UV-LED and Baader UV-Pass Filter]All UV photographs have the same exposure.Photos may be clicked up to 1000 pixels wide. 1. 2a. 2b. Unresized extract from preceding photo, center area. 3. 4a. 4b. Unresized extract from preceding photo, stigma. 5a. 5b. Unresized extract from preceding photo, foreground petal. 6a. 6b. Unresized extract from preceding photo, topmost petal. Set 2Middletown, New Jersey, USA13 February 2015Cultivar from garden store Equipment [Nikon D600-broadband + Rodenstock 60mm f/5.6 UV-Rodagon]The EXIF data in the photographs is incorrect for the lens focal length and lens speed because this lens is unchipped. Ultraviolet Light [f/11 for 3" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter] Ultraviolet Light [Extract from preceding photo] Ultraviolet Light [f/11 for 1/30" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]Conversion in Photo Ninja. Ultraviolet Light [Extract from preceding photo] Ultraviolet Light [f/11 for 1/30" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]Alternate conversion in Capture NX2. Link to comment
colinbm Posted February 10, 2015 Share Posted February 10, 2015 Lovely flower & photography AndreaI like the up close detail you have captured.Is the conical cell iridescence, in visible & UV ?Col Link to comment
Andrea B. Posted February 10, 2015 Author Share Posted February 10, 2015 Thanks, Col. "-) I can see a sheen on the petals in Visible light caused by the conical cells. But the colour change is minimal - more of a lighter/darker thing. In the Vis photo, the shininess is not so evident because the photo was made in soft non-directional light. (Well, to be precise the ambient lighting was more from the front than the back.) The UV LED torch used as a raking light really brings out the surface in UV. The UV wavelengths are shorter, so are more refracted by conical cells and thus produce a bit more colour change. ****************** That Rodenstock Omegaron enlarger is a very sharp little cookie of a lens. I was very pleasantly surprised by the sharpness and detail I got in these photos. I only paid $30 for it. Of course, it requires a helicoid and step rings and so on which does add a bit to the price. Link to comment
DaveO Posted February 10, 2015 Share Posted February 10, 2015 Excellent images Andrea.What happens if you use flash? Do you still get UV-blue in the same places?Dave Link to comment
nfoto Posted February 10, 2015 Share Posted February 10, 2015 Very good examples for showing iridescence effects of conical cells. In order to make this apparent, sufficiently high resolution is alpha and omega. Fortunately our UV methodology has advanced to such a stage by now. Link to comment
JCDowdy Posted February 10, 2015 Share Posted February 10, 2015 Andrea, These are really nice, especially UV#2b, what is the reproduction ratio on these photos? Also I recall you were working on blocking light leaks and filter mounting for this, or a similar, enlarger lens. What is the filter set-up on this lens? Link to comment
Andrea B. Posted February 10, 2015 Author Share Posted February 10, 2015 Dave, excellent question. I plan to reshoot the African violet while it is still in bloom using my UV-flash which of course has a broader output of UV light. This violet only seems to bloom once a year so I should catch it while I can given that it has such gorgeous conical cells. Bjørn, thanks. "-) I may eventually have to re-purchase that CO 60 for its sharpness/resolution. JD, this was the Rodenstock Omegaron 50/3.5, an EL, which seems not to leak any light thru its aperture windows in the particular set up I was using - a helicoid and clamp filter-holder combo - about which I will post in a separate thread. You have reminded me that it would be nice to include a photograph of a ruler in future work so that the magnification factor could be determined. The Omegaron and its cousin the Rodenstock Omegar 75/4.5 (also an EL but with no aperture window) seem to be my poor man's Rodenstock 60/5.6 UV-Rodagon - my lens which does indeed leak light thru its aperture windows unless they are stopped up. (poor woman's? poor girl's? smile) It might be nice to set up a 3-way test of these Rodies. Link to comment
JCDowdy Posted February 10, 2015 Share Posted February 10, 2015 JD, this was the Rodenstock Omegaron 50/3.5, an EL, which seems not to leak any light thru its aperture windows in the particular set up I was using - a helicoid and clamp filter-holder combo - about which I will post in a separate thread. ............ The Omegaron and its cousin the Rodenstock Omegar 75/4.5 (also an EL but with no aperture window) seem to be my poor man's Rodenstock 60/5.6 UV-Rodagon - my lens which does indeed leak light thru its aperture windows unless they are stopped up. (poor woman's? poor girl's? smile) It might be nice to set up a 3-way test of these Rodies. I have worked out a way to mount them that blocks the leak and involves no glue and allows rear mounting of 1.25" filters. I need to post it so you can consider using it in your Rodenstock comparison. Link to comment
Andrea B. Posted February 10, 2015 Author Share Posted February 10, 2015 "Them" being what lenses? :P(But let's start a new thread for that.) Link to comment
Andrea B. Posted February 15, 2015 Author Share Posted February 15, 2015 Dave, I added a set made with UV-flash to the original post. They also show iridescencent areas. Link to comment
DaveO Posted February 16, 2015 Share Posted February 16, 2015 Thanks,I asked if there was any change using UV-modified flash vs UV-LED as I thought (obviously incorrectly) that UV-LED lighting tended to be monochromatic compared to flash. I've never used UV-LED outdoors because of subject movement with the longer exposures. Does a flower which gives UV-yellow to flash still give UV-yellow to 365 nm LED?Dave Link to comment
nfoto Posted February 16, 2015 Share Posted February 16, 2015 The false-colour yellow in UV does exist with a 365 nm LED light source, but is less distinct. Link to comment
Andrea B. Posted February 16, 2015 Author Share Posted February 16, 2015 In photos made with the Nichia 365nm UV-Led I do still get the false colour blues & yellows but usually in a much less saturated form. The yellows are paler and the blues grayer. It is difficult to use UV-Led torches outside because unless you do some "painting with light" using the torch, the lighting looks blotchy because it does not quite overcome the strong light from the sun. But to paint with light you need longer exposures and longer exposures are not desireable when the breezes are rambling around thru the flowers. "-) Link to comment
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