Monday, 10 June 2013

European spindle (Euonymous europaeus): UV reflexion and UV-induced visible fluorescence.

So far, I have published only images that show the UV-reflexion of flowers. However, some flowers show also very interesting UV-induced visible fluorescence. The latter can be documented by illuminating the flowers with UV-light in the dark, or at least under dim light conditions. Photographing fluorescence does not require a modified camera, since visible light is captured. Using an appropriate light source and the setting the white-balance has a significant effect of the appearance of the photos. I will write about this in more detail later, after acquiring some more experience. For now, just an example.

First, the visible light image:

Second the UV-photo using the Baader U-filter. The sun was the only light source. The petals have a UV-reflecting base but are mainly UV dark towards the tips.

Third the flower illuminated with a LED-UV-torch with a peak output at 365 nm (photographed in the dark):

Even with some background illumination the UV-induces fluorescence is visible:


  1. Unfortunately most of that "UV induced visible fluorescence" shown is blue leakage from the used UV LED that those LEDs all have, even the 365nm Nichia LED. Needs proper filtering, then the results will look much better.

  2. Klaus,
    many thanks for your comment. I admit that I have limited experience with UV-induced fluorescence. Therefore, I much appreciate your input.
    For these shots I had put a UV-A transmission filter (from Optik-Makario, should be similar to Schott UG11) in front of the UV-torch. What filtration would you recommend?
    Despite the fact that there might be blue leakage in my images, I’m pretty confident that there is also fluorescence, since other white flowers or other white surfaces do not appear that bright under the same light. (Which should be the case for pure reflexion of blue light.)
    Best regards,