All that glitters...

[enricosavazzi]

A good example of the difference that a Convoy UV flashlight can make, even when mixed with a powerful studio flash at an exposure around 1/4 s.

 

Sony A 7 II, UV Rodagon 60 mm, Baader U, Bowens 1500 Pro with original uncoated tube and shield, Convoy 365 nm torch (only in the first of two shots).

 

The subject is Hypericum perforatum. The first shot with flash + Convoy, the second with flash only. The difference in false color is evident, in particular the golden glitter of the blossoms.

 

 

[Andy Perrin]

Love the second one particularly. The first one does have more gold in it, but I like the purples in the background of shot 2.

[Cadmium]

I get that UV gold look outdoors sometimes, with just natural lighting. Never figured out what it is caused by.

I have often thought it was the time of day maybe, but I don't know.

Example:

[enricosavazzi]

My best guess is that you will see more "gold" if you add UV radiation at about 350-365 nm to the ambient illumination, or selectively reduce the level of longer UV wavelengths (380-400 nm). Time of day and/or season may have something to do with it, since during the day the UV spectrum may change, together with UV levels. Weather certainly does affect the UV spectrum. Most of the time, clouds or haze do selectively reduce the levels of the shorter UV wavelengths.

 

Specular surface reflection, on the other hand, is a property of the subject that does not seem to be strongly wavelength-dependent. A reflective subject does enhance the "golden" impression.

[Andrea B.]

Enrico, I have also noticed the increase in golds/yellows when using a 365nm UV-LED outdoors. (There's a post on here about it but I don't remember where.) My usual problem with supplementary UV from a UV-LED is that the coverage is not wide, so I get a flower or other subject looking false-golden but not the flower surroundings. And it is sometimes difficult to properly blend the background with the flower where there is overlap from the UV-LED. Wide painting with the UV-LED torch, as you have done I think, is needed to avoid these mismatched areas.

 

And, as you have noted, many factors play into the capture and its processing. Sometimes a small turn of the color wheel when converting or a slightly different placement of a white balance dropper can change the color cast of the background or the subject. If one rigorously uses a white balance standard and camera/lens profiling, then that helps uniformity of results. But we don't always want uniformity!! I don't anyway. :D :D :D

 

****

 

Cadmium, if you white-click your background in Photo Ninja, then the gold all disappears and the flowers turn a beautiful blue. So your result is probably just an outcome of the way you performed your white balance. Of course, I cannot be sure.