Rubies seen through 'crossed' filters
A set of synthetic rubies seen through a deep-red filter (RG715) and illuminated with blue light (6500K LED + 5mm/BG38). The camera only sees light arising from the chromium fluorescence from the rubies. This is what is known as the 'crossed-filter' technique which is a very sensitive way of detecting fluorescence (especially red).
The Sony camera in 'night-shot' mode has very high sensitivity at the wavelength of the ruby fluorescence (694nm).
Flickr page for this photo.
Visit the Eye for Science Flickr group.
Visit our Facebook app profile page.