It’s not often that you get to see the world in a totally new way. So my first dive to view fluorescence in underwater creatures was really mind-blowing. Fluorescence is commonly confused with bioluminescence, the simple difference being that bioluminescence refers to light generated from within the organism, while fluorescence requires an external stimulus, in this case light.
In order to view fluorescence, you need a light source (flashlight, camera strobe) and special set of filters – one for the light source and one for the viewer (your eyes, camera lens). I use filters from NightSea. The filter on your light source is called an exciter filter. It is calibrated to only allow let through wavelengths that will excite the fluorescent pigments. The exciter filter is blue/purple. The filter on the camera lens or in the visor you wear over your mask is called a barrier filter. The barrier filter is calibrated to block the exciter wavelengths so that the only light seen by the camera is the fluorescence. The barrier filter is yellow/orange (opposite of blue/purple). My barrier filter is inside my camera housing, so I am fully committed to photographing fluorescence for that dive!
So what is it like diving with all these filters everywhere? Pretty weird. It adds a totally new dimension to night diving. Your vision can be in one of four states at any given time: no filters (normal night dive), exciter filter only (everything looks blue), barrier filter only (everything looks yellow), or both filters on. Your world goes black when both filters are active. Inky black. The glow from fluorescence is a very faint greenish glow and not much to navigate by. In the photographs you can clearly see the differential in light coming from the subject and background or substrate. For my camera settings this means f2.8, ISO 1600, shutter just fast enough to get sharp images, strobe dumping a full charge every shot.
Creatures that look quite ordinary during the day now take on otherworldly colors. Giant sea anemone tentacles look light green or tan during the day; at night they glow brilliant green and wouldn’t look out of place at a rave. Bearded fireworms look quite festive. Lizardfish blend in with the sand during the day, when hit with the exciter source they look like radioactive fish that swam too close to the nuclear plant. Coral polyps glow with variety of colors. Hope this was enlightening! I’ll show myself out.