Colutea arborescens [Bladder Senna]

[nfoto]

Rørslett, B. 2014. Colutea arborescens L. (Fabaceae). Bladder Senna. Flowers photographed in visible and ultraviolet light. http://www.ultraviol...-bladder-senna/

 

 

A bush or low shrub up to 3 m tall, occurring on dry meadows and rocky outcrops in Continental and Eastern Europe. It is also used as an ornamental plant and has been introduced in Northern America.

 

Material from Lovćen nature reserve, Montenegro. 24 June, 2014.

 

image reference: COLE_ARB_G1406241218_VIS.jpg

Visible light: Nikon Df, Voigtländer 125 mm f/2.5 APO-Lanthar, daylight.

 

Image reference: COLE_ARB_I1406241723_UV.jpg

Ultraviolet light: Nikon D3200 (modified), Coastal Optics 60 mm f/4 APO lens, internal Baader U2" (Venus) filter, SB-140 flash.

 

The very prominent UV-dark marks on the upper petal loosely corresponds to a reddish outlined region of the corolla.

 

A lot of beetles, flies, and bees were visiting these flowers.

 

[Published 28 June, 2014]

[nfoto]

Andrea kindly commented on a possible colour cast in the UV capture of C. arborescens. I plan to add a few more UV examples when time allows and shall address the issue then.

[Andrea B.]

I was curious about the purple. (Or violet if that is what it is properly called.) It appears to me that there is a magenta cast to this photo.

 

We have tried to create a standardized look for presentation of our UV signatures so that illustrations from different cameras would look the same - as best can be accomplished. This does make the assumption that a Baader-U is in use for the UV shot. And further that a typical Bayer filter is present in the camera. Of course, each combination of camera+lens+filter+lighting will give variations.

 

Our current Best Practice would be to photograph a white standard and colour patch card for each session (each flower). In circumstances where that is not possible, well, then wing it !! B)

 

If Bjørn's photo is taken into Photo Ninja and Magenta is turned off (fully desaturated) on the Color Enhancement page, then it looks like this and the purple becomes a very dark blue.

 

If you move the Magenta (325) slider -60 so that it becomes Blue (265), then the photo looks like this and the dark blue is a bit more obvious. (And rather pretty, imho.)

 

[i note for the record that desaturating either the Blue slider or alternately the Red slider did nothing to the photo. So it is a Magenta cast we are dealing with I think.]

 

Of these three photos, which is correct? There is no answer. This is false colour.

We aim for blues and yellows and sometimes some greens in our converted UV signature photos, but this is currently an art and not a hard-and-fast science. I personally prefer no purples or magentas if that is possible. But, as they say ---- ymmv. ;) B)

[colinbm]

"ymmv" depending on your monitor ?

Col

[Andrea B.]

Gotta have a profiled/adjusted monitor or ya can't be in this business for sure !! B)

Gotta also understand a bit about colour management - colour spaces and colour profiles.

 

Thus ymmv = your mileage may vary. Not = your monitor may vary. ;) ;) B) B)