Using sunlight or shadow in reflected ultraviolet photography

Today shots of a R. fulgida flower, but is about some principle observations when doing reflected ultraviolet photography in sun or shadow. I was using my "work horse" UV filter, the Baader-U filter. Lens was my CERCO 94mm quartz flourite lens. Light source was sunlight resp. shadow / blue sky at around 1800 hours (early evening). All shots were done at about f5.6.

[click on image to see a larger one]

Visible light image - Sunlight  

UV image using Baader-U filter (approx. 320-395nm, effective peak approx. 375nm) - Sunlight:  

Visible light image - Shadow  

UV image using Baader-U filter (approx. 320-395nm, effective peak approx. 375nm) - Shadow:  

Quadriptych of the above images for comparison:  

Quadriptych of the above images for comparison (detail):  


I had the rare chance to find about identically looking R. fulgida flowers just a few centimeters apart, one in sunlight and one in shadow, when I noticed how different the UV results looked like. Comparing the images taken in sunlight or in shadow (blue sky being the only UV source), the latter UV image shows much clearer details and more even exposure. It comes at a steep difference however, 2.5EV (stops) more the shadow image took.


Stay tuned, more will follow on that fascinating subject...