nfoto Posted June 12, 2013 Share Posted June 12, 2013 Rørslett, B. 2013. Potentilla anserina L. (Rosaceae). Silverweed. Flowers photographed in visible and ultraviolet light. http://www.ultraviol...ina-silverweed/ Potentilla anserina L.Syn. Argentina anserina (L.)Rydb. NO: GåsemureSE: GåsörtDK: Gåse-PotentilFI: Ketohanhikki IS: Tagamura DE: Gänse-Fingerkraut EN: Silverweed P. anserina is a small creeping herb, having a wide circumboreal distribution in different races (ssp. anserina, ssp. egedii (Wormsk.)Hiit.). It thrives on sandy soils mainly along coastlines and can stand a level of trampling few other species can manage. Small and large pollinators frequent the large, deep yellow flowers borne on long stalks from the rhizome. Flowering is late spring to early summer and can continue into the autumn. The plant has been utilised for medical and nutritional purposes. Together with P. erecta, P. anserina has been instrumental to my getting involved in UV photography. Both species show prominent marks under UV light. I have photographed both species over a period of 2 decades, first on film, then digital. While the results visually differ, they in fact show exactly the same underlying UV signature. Specimens of P. anserina were collected at various locations near Oslo, Norway 1999-2012. They all belong to ssp. anserina. The northern race ssp. egedii is only found north of the Polar circle in Norway. I hope to be able to document ssp. egedii later this year. Image reference: POTE_ANS_D990618915_VIS.jpgVisible light: Nikon F5, UV-Nikkor 105 mm f/4.5 lens, Tiffen Hot-mirror filter, Fuji Velvia film. Daylight. Image reference: POTE_ANS_D990618923_UV.jpgUltraviolet light: Nikon F5, UV-Nikkor 105 mm f/4.5 lens, Nikon FF filter (Wratten 18B equivalent), Fuji RTP film, daylight. The colour balance of the tungsten film (RTP) makes highly UV-reflective areas come out in near white whilst the UV-dark patches are red. The latter is caused by the filter's leakage in IR that already commences in the deeper red band. Taken all together this characteristic makes for striking images. To compare to modern digital UV footage, transform the red into dark grey or black. Image reference: POTE_ANS_S990618720_UV_BW.jpgUltraviolet light: Nikon F5, UV-Nikkor 105 mm f/4.5 lens, Nikon FF filter (Wratten 18B equivalent), Ilford XP2 b/w film, daylight. Using b/w film for UV flowers results in images very similar to today's digital UV, but without colours of course. Image reference: POTE_ANS_I1006060407_UV.jpgUltraviolet light: Nikon D40X, Coastal Optics 60 m f/4 APO lens, Baader U2" (Venus) filter, SB-140 flash. The digital capture above shows the identical UV signature to the film-based images. Image reference: :POTE_ANS_I1206010293_UV.jpgUltraviolet light: Panasonic GH-2, Coastal Optics 60 m f/4 APO lens, Baader U2" (Venus) filter, daylight. This overview indicates that older flowers change their UV-appearance from yellow to near white. Thus, the high UV reflectivity of the petals is unchanged, but the spectral peak within the UV band no longer shows the yellow cast. This might indicate that substances causing the yellow colouration are degraded or leaked out as the flower ages. [Published 12 June 2013] Link to comment
Andrea B. Posted June 12, 2013 Share Posted June 12, 2013 A very interesting post! Thanks for showing the older film-based UV fotos. Link to comment
nfoto Posted June 12, 2013 Author Share Posted June 12, 2013 Over time, progress should add more sophisticated and improved methods, but that on its own does not entail all lessons from the past are to be discarded. The striking red bull's eye pictures continue to attract buyers. Link to comment
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now