colinbm Posted November 12, 2013 Share Posted November 12, 2013 My home grown Allamanda runner flower. This was grown from a cutting, thanks to my Mum :DThanks to Wikipedia we have http://en.wikipedia.org/wiki/AllamandaAllamanda cathartica.These are a 40mm deep trumpet flower. This was taken with a Sigma DP2 converted to full spectrum & with the addition of an Astrodon UVenus filter to exclude all light except UVA from the cameras sensor. Visible light. This is the Sigma DP2 full spectrum compact used to capture this photo of the Allamanda flower.It has a AstroDon UVenus filter in front of the lens & I have used a automotive 50watt HID lamp, which while they are advertised as Xenon are actually a Mercury Gas Discharge Lamp & has the usual mercury emission peak at 365nm, which is useful to illuminate the subject in UV light too. CheersCol Link to comment
nfoto Posted November 12, 2013 Share Posted November 12, 2013 The UV-dark patch makes the inner deeper yellow area of the corolla. An interesting signature. I disclose my ignorance with respect to the Sigma camera - does it have a fixed lens or can the lens be exchanged for something more transparent to UV? Link to comment
colinbm Posted November 12, 2013 Author Share Posted November 12, 2013 Thanks for your interest BjornThis is the fixed lens Sigma DP2 compact, the lens is not changeable.I use this mostly for my experimenting as it has 'live view' which I find useful for out of visible spectrum photography.It does have the same APS-C sensor as the Sigma SD15 dSLR, which I also have.I have tested the lens for transmittance to UVA & it seems to be getting down to the 365nm mercury emission line.The unknown with the camera is the transmittance of the cover glass on the sensor & the transmittance of the micro lenses on the sensor ??When I get an older Sigma SD9 dSLR I will do some more tests on the glass cover on the sensor & replace it with a quartz cover & see the results in a few weeks.CheersCol Link to comment
nfoto Posted November 12, 2013 Share Posted November 12, 2013 I found some UV shots of Allamanda neriifolia taken some years ago and they indeed replicate the UV features shown here. I had forgotten this species was documented. Link to comment
JCDowdy Posted November 13, 2013 Share Posted November 13, 2013 Col, Nice little portable HID lamp you have set up there. I have been thinking of building one from an little 12V AutoZone headlight conversion kit. I recall the lamp I was looking at was claiming to be Xe but now you have me wondering it is is actually a Hg Xe. John Link to comment
colinbm Posted November 13, 2013 Author Share Posted November 13, 2013 Thanks JohnYes, the labelling of Mercury inside a produce is not too desirable these days !But these lamps have some useful UVA output.CheersCol Link to comment
colinbm Posted January 2, 2014 Author Share Posted January 2, 2014 I have been looking for some material on the reproduction of the Allamanda flower, without much luck.The reproduction parts of the Allamanda flower are hidden from view inside the base of the flower.I have found a reference that would suggest that wasps & ants are the main pollinators.http://onlinelibrary...030512/abstractQuote "The nectar is coming out through stomata and it contains an equal concentration of glucose and fructose. The major visitors to suck nectar are wasp and ants."Some description of reproduction & a cut cross section are here.... http://www.backyardnature.net/yucatan/allamand.htmCheersCol Link to comment
Andrea B. Posted January 2, 2014 Share Posted January 2, 2014 Those are good links, Col. I think you should work on a formal write-up for your Allamanda so we can post it in the botanical section somewhere. While we cannot manage to produce a "standardized colour" from your SigMerril fotos,you could simply use a nice black & white version of the UV foto in a formal post. Link to comment
colinbm Posted January 3, 2014 Author Share Posted January 3, 2014 Thanks AndreaI am learning fast (I hope).Learning biology & getting the best UV out of the camera.The Andrea-U filter is working out good, just need to cut a bit more IR leak.What is the filter combination in the Andrea-U ? Perhaps I should get a different IR cut filter to cut the small leak in IR ?OR find out where I can purchase the new VG20 IR blocker in 52mm filter ring or 50mm dia ??CheersCol Link to comment
nfoto Posted January 3, 2014 Share Posted January 3, 2014 You can contact Reed F Curry for the filter details. (he is a UVP member). Link to comment
colinbm Posted January 3, 2014 Author Share Posted January 3, 2014 Thanks very much BjornPage 13 of this presentation http://www.us.schott.com/advanced_optics/english/download/schott-vg20-nir-absorbing-optical-filter-glass-2013-us.pdfhas the BG39 as having a better IR attenuation then the VG20 ?I am a bit confused now ? I can see they have different thicknesses, but that would make the VG20 less transmissive in the UV ?CheersCol Link to comment
nfoto Posted January 3, 2014 Share Posted January 3, 2014 Thickness is the critical parameter as overall transmission in any spectral band is attenuated by "depth" (ie filter thickness) Link to comment
Andrea B. Posted January 3, 2014 Share Posted January 3, 2014 I would go with a BG 39. For one thing, it is available pre-mounted from various sellers. And I have not yet seen the newer VG20 sold as a mounted filter. It is possible that the VG20 glass is being manufactured for use as an internal hot mirror for digital devices, so may not make it into a filter mount? Remember that what you want to do is have the IR-blocker cover the range where your UV filter may transmit tiny bits of IR. Thus if an IR-blocker transmits IR way out past 1200nm and the UV filter does not, then there are no worries. The Ebay seller uviroptics might have an uncoated BG39 filter available. (Or an S8612). And the B+W company has a pre-mounted, coated BG 39 filter for sale from various retailers. I think with the Andrea-U a .75mm or 1.0mm thickness will suffice. Link to comment
colinbm Posted January 4, 2014 Author Share Posted January 4, 2014 Thanks Andrea & BjornThe eBay seller has got my order.CheersCol Link to comment
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