Coral reefs enchant when one dives in fluorescence

by   Profile Mares   When 10th February 2017
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Under blue light, the flathead (platycephalidae), which is brown in daylight, appears a fluorescent pink. (c) Prof.Dr.Horst Grunz
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Under blue light, the flathead (platycephalidae), which is brown in daylight, appears a fluorescent pink. (c) Prof.Dr.Horst Grunz
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Corals seen with fluorescence lighting (c) Prof.Dr.Horst Grunz
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Corals seen with fluorescence lighting (c) Prof.Dr.Horst Grunz

Adventures in fluo-diving in Abu Dabab

No, it wasn't the Pink Panther, but a pink flathead that was the highlight in Abu Dabab in December 2016. Under blue light, the flathead (platycephalidae), which is brown in daylight, appears a fluorescent pink. Twenty-five divers went on a total of 18 night dives with fluorescence lighting, using a new blue light and mask filter. They came away describing the underwater world as magical, impressive and overwhelming.

As a biologist, videographer and diver, Prof. Dr Horst Grunz has been diving using fluorescence lighting since 2007, having invented the world's first HighPower underwater fluorescence torch. The technology was intregrated into lighting manufacturer TillyTec's new Maxi Uni series. Dr Grunz, behind his US colleague Charles Mazel (founder of Nightsea and consultant of Light & Motion) is the person with the most experience in the area of underwater fluorescence.

Mazel and Grunz maintain that only by using blue light (450-465 nm) and a built-in dichroic glass filter would there be no problems with the resultant image. In contrast to polyester films, this interference filter has a high transmission rate for specific wavelengths. This explains the sheer brilliance of the fluorescent colours. The same goes for flashes with 5500° Kelvin, with which only the dichroic glass filter and integrated special foil are suitable. In contrast to polyester films (60%), the dichroic filter and special film reduce the intensity of the flash by just 40%.

Offered with the UV LEDs, the luminaires, with their impossibly low prices, would prove irresistible even for beginners. These include multi-function luminaires, which almost always do not contain royal blue LEDs. Technically, a dichroic filter is not usable because its blue would cover the white and red LEDs. Another important factor for shooting images with good fluorescence is the yellow barrier filter for the camera and mask. That is why Horst tested numerous yellow filters when he was in Abu Dahab (https://youtube/uiBscbURex8). Also, in using barrier filters (LEE, etc) for polyester films, one would hope to photograph a beautiful picture. As such, it would be acceptable that the filter allows a certain proportion of blue light to pass through.

The condition of coral reefs is an important topic in fluorescence diving. Using this fluorescence technique, analysing coral reefs is easier than doing it during the day over large areas. This involves checking on the distribution of individual coral species, and partial or completely dead coral blocs. Particularly important is the detection of tiny 1mm large coral settlers (they are considered the new hope for the reef's regeneration), which are not visible amongst the corals during the day. Under fluorescence, they appear as greenish-yellow spots from several metres away.

In summary, it can be said that fluorescence dives are not only a magical experience for scuba divers, but they are also an important method of checking the condition of coral reefs.

To stay safe during fluorescence dives, a complete set of equipment includes:

1. Blue light lamp with royal blue LEDs (450-465 nm) and built-in dichroic filter
2. Yellow camera filter arc
3. Yellow mask filter (FlipUp filter)
4. Filter to convert white light to blue light (flash and white LEDs)
 
Further information is available at: horst.grunz@uni-due.de 
Video: https://www.youtube.com/watch?v=SO-5F_K5s7o

Information Abu Dabab on Taucher.Net

Written by
Profile Mares
Date
When 10th February 2017
Where
Location El Malikia Resort Abu Dabbab, Egypt

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