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Saintpaulia sp. [African Violet]

Conical Cells
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#1 Andrea B.

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Posted 10 February 2015 - 03:35

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 1
Middletown, New Jersey, USA
07 February 2015
Cultivar 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.
Attached Image: saintpauliaVisFlash_20150207wf_29423pn1.jpg

Unresized extract from preceding photo, anthers.
Attached Image: saintpauliaVisFlash_20150207wf_29423pn2.jpg


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.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29447pn.jpg

2a.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29451pn.jpg

2b. Unresized extract from preceding photo, center area.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29451pn02.jpg

3.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29455pn.jpg

4a.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29465pn1.jpg

4b. Unresized extract from preceding photo, stigma.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29465pn101.jpg

5a.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29471pn1.jpg

5b. Unresized extract from preceding photo, foreground petal.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29471pn101.jpg

6a.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29475pn1.jpg

6b. Unresized extract from preceding photo, topmost petal.
Attached Image: saintpauliaUVBaad365UVLED_20150207wf_29475pn101.jpg

Set 2
Middletown, New Jersey, USA
13 February 2015
Cultivar 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]
Attached Image: saintpauliaSpUVBaadSB14_20150213wf_29652pnPf.jpg

Ultraviolet Light [Extract from preceding photo]
Attached Image: saintpauliaSpUVBaadSB14_20150213wf_29652pnPfExtract.jpg

Ultraviolet Light [f/11 for 1/30" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]
Conversion in Photo Ninja.
Attached Image: saintpauliaSpUVBaadSB14_20150213wf_29676pnPf.jpg

Ultraviolet Light [Extract from preceding photo]
Attached Image: saintpauliaSpUVBaadSB14_20150214wf_29676pnPfExtract.jpg

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.
Attached Image: saintpauliaSpUVBaadSB14_20150213wf_29676pf.jpg
Andrea G. Blum
Often found hanging out with flowers & bees.

#2 colinbm

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Posted 10 February 2015 - 04:07

Lovely flower & photography Andrea
I like the up close detail you have captured.
Is the conical cell iridescence, in visible & UV ?
Col

#3 Andrea B.

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Posted 10 February 2015 - 05:58

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.
Andrea G. Blum
Often found hanging out with flowers & bees.

#4 DaveO

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Posted 10 February 2015 - 08:58

Excellent images Andrea.
What happens if you use flash? Do you still get UV-blue in the same places?
Dave

#5 nfoto

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Posted 10 February 2015 - 14:13

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.

#6 JCDowdy

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Posted 10 February 2015 - 14:38

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?

Edited by JCDowdy, 10 February 2015 - 14:39.


#7 Andrea B.

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Posted 10 February 2015 - 16:33

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.
Andrea G. Blum
Often found hanging out with flowers & bees.

#8 JCDowdy

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Posted 10 February 2015 - 18:00

View PostAndrea B., on 10 February 2015 - 16:33, said:

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.

#9 Andrea B.

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Posted 10 February 2015 - 18:33

"Them" being what lenses? :P
(But let's start a new thread for that.)
Andrea G. Blum
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#10 Andrea B.

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Posted 15 February 2015 - 05:56

Dave, I added a set made with UV-flash to the original post. They also show iridescencent areas.
Andrea G. Blum
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#11 DaveO

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Posted 16 February 2015 - 00:12

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

#12 nfoto

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Posted 16 February 2015 - 10:15

The false-colour yellow in UV does exist with a 365 nm LED light source, but is less distinct.

#13 Andrea B.

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Posted 16 February 2015 - 19:12

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. "-)
Andrea G. Blum
Often found hanging out with flowers & bees.