The latest superbright lights are proving particularly suitable in the demanding world of underwater video and photo shooting. American underwater housing specialist Fantasea has used these up-to-the-minute LEDs in its latest lamp, and thrown in some nifty lighting modes as well. I integrated one into my camera system to give it a go.

The Design
The Radiant Pro 2500 is a slim tubular light that can be handheld or mounted via a YS adaptor and integrated into a camera-arm system. The lighting head on the Radiant Pro’s body is constructed from marine-grade aluminium with a bright blue anodised finish, and the slim rear battery-holder is built from high-grade gloss black polycarbonate.
The two sections are connected via a screw thread, with a double O-ring seal giving the lamp a maximum depth-rating of 100m. Power is supplied from twin removable and rechargeable 18650 li-ion batteries, with two spares provided along with a charger and mains adaptor, and a wrist lanyard and clip to help avoid loss.
The lamp has a single multi-functional push-switch mounted within the head, with a colour-coded illuminated ring indicating battery state.

Lighting Modes & Outputs
The lamp uses no fewer than 12 LEDs, offering choices that include two white-light modes.
The wide mode delivers a 120° beam at 100% power (2500 lumens), 50% (1250 lumens) and 25% (625 lumens).
A narrow 15° spot beam offers the same three output settings. The white light has a colour temperature between 5300 and 5600° Kelvin.
Red LEDs deliver a wide 120° beam with two power settings of 100% and 40%. An ultra-violet (UV) mode has a single output setting, again with a 120° beam angle. The actual outputs of the red and UV modes were not available.
The lighting options are enhanced with safety modes. The Radiant Pro will flash as a slow strobe or as a “dot-dot-dot-dash-dash-dash” Morse code SOS signal in both white and red light modes.
Burntimes range from a claimed 50 minutes at 100% power (white light) up to eight hours of continuous SOS flashing from a fully charged battery set.

In Use
I took the Radiant Pro 2500 with me on a trip to Mauritius, which promised to be a high-yield Indian Ocean photo destination offering plenty of subjects at which to point a stills or video camera, and an effective proving ground for this multi-function tool.
I used it first as a spotting light. In the red beam mode I could see clearly under dark overhangs and in nooks and crannies to find shy, elusive subjects for my memory cards. The red light proved the most useful, and with power output at the minimum setting the wild marine creatures seemed unfazed by the illumination, and didn’t scurry away to hide.
The white light seemed a bit harsh for spotting purposes, and some of the subjects resembled rabbits frozen in car headlights.
The next task was to see if the white light alone could be used to capture stills and video in the bright ambient light found under water in the middle of the day.
The short answer was “yes, it could”. Although a pair of lights would have been more attuned to the task, a single light set to wide beam on full power coupled with an increase in ISO in my camera settings produced pleasing, well-lit subjects.
I found that narrow field-of-view macro lenses gave the best results, with the single light struggling to illuminate the full 180° coverage of my fisheye lenses.
Dusk is my favourite time to be under water with a camera, but reduced ambient light levels create a problem for most photographers at this time of day. The subjects are lost in shadow, without any visible contrast onto which autofocus systems can lock. This is when a good-quality torch proves its worth.
With the Radiant Pro used in white-light mode the camera could easily detect the subject and produce sharp, in-focus images. However, shy subjects seemed easily spooked by the intensity of the beam, turning their tails to the bright light or scooting away to find cover.
By using the red beam in conjunction with separate strobe lights, I found that I could easily focus without scaring the subjects. The flash from the strobes overpowered the red light, leaving it invisible in the final images.
As dusk turned into night, I started to use the UV mode. Flora, fauna and some marine animals give off fluorescent proteins that glow when excited by ultra-violet light, although to get the full effect a yellow mask filter is required, and to record the effect on camera a yellow lens filter is needed.
The radiant Pro UV mode isn’t the brightest I’ve seen, and I struggled to capture any usable images without pushing the camera’s ISO settings to the max and using slow shutter speeds with wide-open apertures.
This was challenging at best, but I did get some images of a porcelain crab in an anemone that put a smile on my face.
The last mode to test out was the flashing red SOS feature. I had briefed the boat-crew beforehand to avoid instigating a full-on emergency-rescue scenario as I bobbed about on the surface in total darkness, with the light proving to be unmistakably visible to all.

Ease of Use
At first glance, the single push-button control for this torch seemed confusing and perhaps a little daunting. Indeed, on the first dive I ended up in red flashing mode when in reality
I wanted to be using the white spot beam.
It took a bit of practice to get my head around the short-push/long-push method of turning the light on and off or switching modes, but it quickly became second nature.
One pleasing feature is that the light remembers the last mode used when it’s switched off, resuming in that mode when it’s next switched on.
The battery-power indicator was a godsend, changing through green when fully charged to yellow between 60% and 30% capacity and red between 30% and 15%.
Below 15% it gives a flashing red warning, so you’re in no doubt that it’s about to be fully discharged and may leave you in the dark.

Conclusion
I found the Radiant Pro 2500 an extremely versatile tool. It could be used as a handheld torch with a tight beam suitable for wreck-diving, a focus light in both red or white modes to assist camera autofocus systems or a stand-alone constant light, successfully illuminating subjects for both stills and video capture.
The UV mode wasn’t brilliant, but with a little perseverance and willingness to push the camera’s limits I still managed some pleasing results.

SPECS
PRICE: £442
DIMENSIONS: 210 x 53mm diameter
WEIGHT: 376g (without batteries)
LIGHT SOURCE: 12 LEDs
MAX OUTPUT: 2500 lumens
COLOUR TEMP: 5300-5600°K
MODES: White wide, spot. Red wide. UV wide. White & red flashing (SOS).
OUTPUT SETTINGS: Wide & spot (white & red) 100%, 50%, 25%. Flashing red 100%, 40%.
BEAM ANGLE: Wide 120°, spot 15°
BATTERIES: Two 18650 li-ion rechargeable
CONTACT: www.fantasea.com
DIVER GUIDE 9/10

See more lights and torches in Divernet Showcase