Fluorescence / UV Underwater Photography

Also known as: Fluoro photography, fluo diving, UV photography, NightSea photography Key practitioners: Charles Mazel (NightSea), Norbert Wu, Alex Mustard, Alex Tyrrell Equipment: Blue excitation light source (e.g., NightSea, Sola Nightsea), yellow barrier filter on lens port, optional yellow mask filter; macro or wide-angle lens

Overview

Fluorescence photography captures the phenomenon in which marine organisms absorb light at one wavelength and re-emit it at a longer wavelength, causing corals, anemones, nudibranchs, and other creatures to “glow” in vivid greens, yellows, and oranges against a dark background. The technique requires specialized blue or ultraviolet excitation lights and yellow barrier filters that block the excitation wavelength while transmitting the fluorescent emission.

While fluorescence in corals has been known to science for decades, its application as an underwater photography technique developed primarily in the 2000s, driven by NightSea founder Charles Mazel’s pioneering work and the availability of affordable LED excitation lights.

History on Wetpixel

Charles Mazel and the scientific foundation (2005)

The earliest substantial Wetpixel coverage was Eric Cheng’s December 2005 article on Charles Mazel’s ultraviolet photography research. Mazel, founder of NightSea, published a paper in Limnology & Oceanography: Methods describing how to photograph fluorescence underwater using the right flash, filters, and digital camera with manual controls. The paper covered technique for underwater use, its limitations, and strategies for maximizing results. Alex Mustard commented that he had also published a paper on the subject in the same journal (^[1]).

Equipment becomes accessible (2013)

Light & Motion announced a fluorescence filter for GoPro in 2013, signaling that fluoro photography was moving from specialist equipment to accessible consumer products (^[2]). NightSea remained the primary equipment supplier, with their fluorescence filters and excitation lights used by most practitioners.

Alex Tyrrell’s Full Frame feature (2013)

Photographer Alex Tyrrell’s Full Frame gallery on Wetpixel showcased 29 fluorescence images from Koh Tao, Thailand, including fluorescing moray eels, corals, nudibranchs, mantis shrimp, frogfish, and hermit crabs. Tyrrell began fluorescence photography in 2010 in the Philippines, noting that “at the time not many divers were using this type of photographic equipment and it has only recently hit the spotlight.” He used a Nikon D7000 in a Subal housing with NightSea filters on Sea & Sea YS-250 strobes (^[3]).

Norbert Wu’s fluorescence legacy (2015)

Norbert Wu featured a fluorescent coral image from Palau as the first entry in his “Favorite Images” series on Wetpixel. The image, taken on 35mm film at 80 feet depth using only ambient light, showed coral fluorescing in the blue-shifted light where “nearly all red and yellow colors have been removed from sunlight.” The image had been featured on Microsoft’s Bing homepage. Wu noted that scientists “still understand very little about the function of fluorescence among corals” — theories ranged from defense against predators to UV sunscreen (^[4]).

Biofluorescence discovery (2015)

Wetpixel reported on scientists finding the first ever biofluorescent reptile in the Solomon Islands, demonstrating that fluorescence research was expanding beyond corals into new taxa (^[5]).

Wetpixel Live primer (2020)

Alex Mustard and Adam Hanlon dedicated a Wetpixel Live episode to fluorescence photography, discussing “the process and tools that are used to create images of this amazing natural process” (^[6]).

Technique Details

How fluorescence works

Certain marine organisms contain fluorescent proteins or pigments that absorb light at short wavelengths (blue or ultraviolet) and re-emit it at longer wavelengths (green, yellow, orange, red). The fluorescent emission is always at a longer wavelength than the excitation — this is Stokes’ law. The effect is most dramatic at night or in deep water where ambient blue light dominates.

Equipment setup

1. Excitation light: A powerful blue LED torch (typically 440-470nm wavelength) or UV light aimed at the subject. NightSea and Sola Nightsea are the most commonly referenced brands on Wetpixel.
2. Barrier filter on lens: A yellow/orange filter mounted over the camera port or lens that blocks the reflected blue excitation light while transmitting the fluorescent emission wavelengths. Without this filter, the blue light overwhelms the fluorescence.
3. Mask filter (optional): A yellow filter over the dive mask so the photographer can see the fluorescence with their own eyes.
4. Strobe filters: Yellow/orange filters on strobes if using flash, to avoid washing out the fluorescence with white light. Alternatively, some photographers use only the excitation light as their light source.

Subjects

Common fluorescing marine organisms include:

• Hard corals: Many species fluoresce brightly, particularly brain corals, mushroom corals, staghorn corals
• Soft corals and anemones: Magnificent sea anemones (Heteractis magnifica) and clownfish-hosting anemones
• Nudibranchs: Some species show unexpected fluorescence
• Crustaceans: Mantis shrimp, hermit crabs, decorator crabs
• Fish: Moray eels, gobies, clingfish, frogfish, scorpionfish
• Cephalopods: Some squid and cuttlefish

Challenges

• Limited light: Fluorescent emission is dim, requiring wide apertures and higher ISOs
• Color accuracy: The barrier filter creates a color cast that may need correction in post-processing
• Subject finding: Many photographers need time to develop an eye for which organisms fluoresce
• Night diving required: Fluorescence is most visible in darkness, adding the logistical challenges of night diving

Forum discussions

Wetpixel forum threads on fluorescence included discussions of specific filter setups, gear recommendations, and image sharing. The thread “Surprising fluorescence” (13 replies) explored unexpected fluorescent subjects, while “Capturing Fluorescence? - Help Needed” (9 replies) addressed beginner questions about equipment and technique. UV/fluorescence shots from Bonaire and other tropical locations were shared in showcase threads.

References

• ^[7] (article)
• ^[8] (article)
• ^[9] (Full Frame gallery)
• ^[10] (article)
• ^[11] (article)
• ^[12] (article)