An Introduction to Fluoro Imaging...
Your night dives will never be the same.
Taken with Sola Nightsea/Jeff Honda
Even if you never had black light posters on your wall as a kid, it is hard not to be spellbound by your first fluorescent imaging dive. If done on a healthy reef with lots of hard coral, the glowing universe that is revealed is simply jaw dropping. The equipment that it requires is not very extensive and the tools have improved considerably from the early days when this was primarily a past time of researchers and scientist. So lets dive into the current options for this special niche of underwater imaging.
Photo Kevin Palmer
The first thing to understand is what happens when these underwater animals go all psychedelic in front of your camera when hit by certain spectrums of light. Bio-florescence has been discovered in more marine animals around the world than anyone would have guessed a couple of decades ago. The cells on the surface of the creature absorb a high frequency spectrum like deep blue or UV and then convert that to a new, lower frequency light that is emitted by the animal - often green, yellow, orange or red. So the animals are actually producing their own light after being stimulated by the barely visible blue wavelength or ultra-violet lighting.
Tools to unveil a new world
As with many imaging techniques, there are different roads to achieve similarly excellent results, so we will cover a number of options along with some essentials.
One of the first solutions to be experimented with, and still one of the most powerful, is to use a special excitation filter on a conventional strobe. This set up will produce a lot of light, but there are some compromises that come with this arrangement. Because the strobes are not producing blue light all the time, the photographer must have a another blue wave length constant light to be able to find the subjects to shoot. The aiming light of the strobe is generally too weak to produce usable light through the dark blue filter. The other factor is that all strobes have different light temperature and spectrum output, so combined with the excitation filter you won't necessarily get the ideal spectrums. But if you already have a good strong strobe, these filters can be the least expensive way to start playing with fluoro.
Photo Kevin Palmer
When you use a blue light source like this, you will get the best results by using a Reference Filter on your camera lens. These are strong yellow filters designed to filter out blue light. So all that blue light that is hitting things that do not Fluoresce can be seen slightly, so the yellow filter cleans that up and makes the fluoro subject pop from the dark. There are yellow filters that fit directly on the camera lens and filters that fit the front port of your underwater housing. They work equally well.
Fluoro with constant lighting:
This is perhaps the easiest style of shooting fluoro. Primarily because "what you see is what you get". With blue or UV fluoro light, a glowing realm is spread in front of you and you can head towards interesting creatures that seem to stand out. If looking in live view, you only need to make basic adjustments until it looks "good" and take the shot. To get an even better view of the potential subjects available; Light and Motion, Ikelite and Fix make yellow mask filters that slip over your diving mask so you experience what the camera will see with its reference filter.
Some of the best Fluoro Lights available today:
The Sola Nightsea is the only Fluoro light that has been directly endorsed by Nightsea that has done considerable pioneering work in the realm of fluorescence imaging. So it is no surprise that it produces excellent results. It is also small, light and simple which is a plus when engaging in a dazzling new environment. A phosphor filter is included which turns the light back to "white" for general light use. The price has come down considerably in the last couple of years making the light a bargain.
Fix makes a fine series of underwater imaging lights with a lot of flexibility - up to 100 power settings, interchangeable heads for multiple uses and real time remaining read out. Existing Fix light owners may be able to just purchase the blue head with phosphor filter which makes it a bargain or purchase the blue light complete. This light is a little more powerful than the Nightsea, but uses blue wave length LEDs instead of a special filter as L&M does on the Nightsea. Both produce Fluorescence, but with slightly different effects.
This Kraken is a jack-of-all-trades kind of light, so while it may not be the best fluoro performer, it can do a lot of things pretty well and represents a good deal for someone wanting a focus light that can occasionally shoot fluoro. It is worth noting that Kraken calls this a UV LED light mode - not a high frequency blue like the other lights mentioned. UV will work best on some animals and blue will work better on others. It is not better or worse on its own merits. UV lights typically do not require a reference filter on the camera lens as UV is nearly invisible. There is also a Kraken 5000 lumen version of this light, but the UV mode is the same.
Keldan F1 Fluorescence Filter for 4X & 8X Lights
If you already own any of Keldan's extremely popular 4X or 8X video lights, these very affordable 450NM filters are a great addition to your imaging toolbox. Pop them on anytime you want to experiment with fluoro. While they don't quite match the performance of Keldan's dedicated fluorescence lights, it is still a great option.
Keldan 4X Blue Fluorescence Video Light
This Keldan is one of the most powerful Fluoro lights available and can produce spectacular effects. If you plan on shooting fluoro a great deal, or intend to shoot fluoro video, the Keldan is well worth considering. The wave length used is one that performs best with a yellow reference filter. The light is still fairly compact and light weight in the water.
Courtesy NSF
Keldan LED Module Blue 450NM 95W & LED Module UV 400NM 55W
For professional shooters lucky enough to own a Keldan 8M video light with interchangeable modules, Keldan makes extremely powerful fluoro light heads for special applications. These include both a Blue and UV option. These are great for larger animal florescence like large eels and sharks.
Photo Kevin Palmer
A few tips for shooting Fluoro:
Since fluoro is always shot on a night dive and our eyes tend to adjust to the amount of light around us, you may be surprised at how sensitive you need to make your camera in order to capture what you are seeing. When you first go down and fire up your fluoro light it seems amazingly bright on a busy hard coral reef. But your camera needs help to "see" this subtle form of light. Yellow and green are the easiest for the camera to register, but orange and red are pretty tough. You will definitely need to raise your ISO, probably in the 400 neighborhood, but sometimes higher. Shoot as open an aperature as you can get away with and still have some depth of field. Try f8 to f11 depending on the camera. Remember you are hand holding your exposure and creating ambient light emitted from the animal. Too slow a shutter speed and your images will be soft. An absolute minimum would be 1/60 of a second, but try for a little higher. Most people will find a forgiving close focus lens like a 60mm macro on DSLRs or 30mm-45mm macro lenses on M4/3 and APS-C mirrorless systems will work well. If you shoot a compact with a fairly close focusing lens like an Olympus TG, you are all set. With compact cameras that don't focus closely, you might want to use a weak close focus wet lens. The reason you want to focus fairly close is that you lose light with every inch of water you shoot through and this is not very strong light!
Shooting coral polyps is a great first subject as they are easy, don't move much and are usually pretty bright. Anemones and tube worms are also great subjects and if you are lucky enough to find a Nembrotha nudibranch or a florescent cephalopod, you are in for some spectacular images. Keep an eye out for scorpion fish as they are often a very deep red.
Those who are use to using histograms to review your exposures on your camera can turn that off. Histograms are largely useless because of the nature of the light and will always show images as underexposed. To that end, if you can clearly see your image when reviewing underwater (remember to slide your mask filter up so that you are not filtering your image), then you are probably exposed well. What to set your camera white balance to? Good question. You may have to experiment a bit with your particular camera. On some cameras Auto seems to work fine, otherwise I would probably try it on daylight. By definition, your colors should appear day-glow and over-the-top, so this is one case where you are not trying to get the image to look "natural".
Photo Kevin Palmer