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LIGHTING
Back in the Swinging '60s, Kodak brought out an infra-red-sensitive film that reproduced images from the heat they gave off and used a system of false colours. It was intended as a tool for aerial reconnaissance.
It was not long before we saw trendy magazine articles illustrated with pictures of familiar subjects reproduced in the unfamiliar colours obtained by using this film outside its intended sphere of use.
Gimmicks rarely hang around for long. Needless to say, we tired of these pictures as quickly as we tired of fashion photographs made using the medical photographer's ring-flash.
Most divers who have been under water at night are aware of the bioluminescence given off by plankton in the water. A vivid memory of mine is that of the three dolphins from outer space that swam at the bow of the sailing vessel on which I was once making night-passage near the Galapagos Islands. They were lit up by the eerie green light given off by the plankton as it passed over their bodies.
Similarly, I remember a bioluminescent green sea-lion that swam around our boat later in the dark, when we were at anchor.
Lots of marine animals and organisms live in association with phosphorescent zooantheles, and simple fluorescence can be found in corals, shrimps, anemones, nudibranchs and fish, even some minerals.
What is the difference between phosphorescence and fluorescence? Well, the first will emit light some time after receiving energy from another light source, while the second emits light only for as long as it is receiving energy.
Fluorescent subjects do not emit light unless they receive light, but they can receive light of one wavelength or colour and emit it as another.
Many coloured dyes used in the printing of packaging use fluorescence to make them especially bright. A particular bugbear of commercial photographers is the bright yellow or green ink used in some packaging that photographs as dull brown.
The trick would be to light up a suitable subject with a suitable wavelength of light that would cause it to fluoresce, and at the same time to stop other visible light from reaching either your eyes or the lens of your camera.
Enter Charles Mazel PhD, who began dabbling (his words) with underwater fluorescence back in 1975 but launched into it in earnest only in 1986. He is a research scientist and founded NightSea to share equipment and techniques with others in the sport and scientific diving communities.
NightSea's BlueStar torch uses the latest in high-intensity LED technology, combined with focused optics, to produce an ultra-bright, ultra-tight beam. It uses three C-cells as batteries, with a burntime of 10 hours. A barrier-filter for wearing over your mask is included.
The photo accessory kit includes an excitation-filter that fits over your flash or video light, and a barrier-filter that screws on to your camera lens (I used the standard Nikon 52mm screw mount). There is also a guidebook to underwater fluorescence photography.
Daylight overwhelms any likely effect, so this is something to try out on a night dive. The effect is also quite weak, so you'll need to position your flash close to a subject. This confines its use almost exclusively to macro-photography subjects.
Under water on a typical coral reef in the Red Sea, I found that without the filter over my mask the BlueStar torch had a particularly penetrative beam. Those back on the boat reported knowing at all times which light source among the many others out there was me.
However, with the mask-filter in place, I was reduced to something akin to an underwater version of a ride on the Ghost Train at the Hayling Island Butlins holiday camp of my childhood.
I was unimpressed then, and I was less than stunned this time. Fewer parts of the coral fluoresced than I had anticipated. Almost without exception the sleeping fish did not seem to fluoresce either, apart from a single dragonet that I found hiding under a rock.
Then, over a sandy bottom, it suddenly seemed as if I had been given the senses of a sting ray. I saw tiny animals hiding in the sand that were totally transparent, and therefore invisible with the normal spectrum of lighting from my traditional diver's torch. They glowed a ghostly fluorescent green when lit by the BlueStar torch and viewed through the mask filter.
Photography proved difficult. I found it impossible to focus my macro-lens-equipped camera. I needed to use white light for this, which was still difficult because the camera lens was fitted with its heavy yellow filter.
I was limited to inanimate subjects, dousing the white light of the focusing light immediately before I released the camera shutter. In fact, overall, it made night-diving rather hard work.
Charles Mazel has obviously pursued the technique over a long period and is now getting some fascinating results. I got him to send me an example of a shot of a bristleworm taken using both white light and fluorescence. If you decide to have a go with the kit, be aware that you may not achieve satisfying results without a period of experimentation.
The BlueStar torch costs around £70, including a barrier-filter for your mask, and a photographic accessory kit with flash exciter-filter and camera lens filter costs around £180.
NightSea, www.nightsea.com
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+ A novel way of seeing things in the dark
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- Will the novelty soon pall?
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These pictures by Charles Mazel show a bristleworm shot using white light (top) and fluorescence
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CAMBANDS
SO HOW DO YOU GO ABOUT TWINNING UP a typical pair of independent cylinders that you might find at a dive centre abroad? Well, you could take a set of steel bands and a spanner with you, but I prefer to use Buddy Twinning Bands and Blocks.
This is far from a new product, but I wanted to revisit it in Tests simply because I have heard all sorts of ill-informed comment about the use of these items and feel the record should be set straight.
Believe me when I tell you that they really work - provided that you have a BC or wing with the requisite four slots in the backpack or backplate.
I have heard people say that the ABS backpack that comes with Buddy BCs is not strong enough to take twin cylinders - to which I reply that has been using Buddy Twinning Bands for every project involving in-water regulator and computer comparisons since we started doing them more than 12 years ago. Never have I, or any of our test divers, experienced any problem with them.
You simply substitute the single camband of your BC for a pair threaded through a curved block. A second pair and another block is used to stabilise the unit.
Make sure that the bands are done up as tightly as possible and, as webbing can stretch when wet, that they are properly soaked first.
Some Buddy wings, notably the Tech Wing and redundant Red Wing, have two sets of four slots so that the tank has maximum attachment, but even my old Buddy Trimix (now called a Trident) with only one set of slots works well with Twinning Bands and Blocks, even though the lower pair of bands is clamped into a totally arbitrary position on the tanks.
The same can be said of all other Buddy BCs - they can all work with independent twins. Of course, if your tanks are connected by a manifold things are less than ideal. Presumably they will be already banded, in which case you can dispense with the blocks.
So what about using twins that are totally independent? Well, cave-divers have been doing that for years. You will need two separate pressure gauges, and to switch regulators during the dive, but what's hard about that? It's the same as diving with two separate aqua-lungs; when others are going in with a single cylinder and regulator set, you have the security of two.
I have even used two cylinders of different sizes, one 12 litre aluminium and one 15 litre steel. In that case I found I had to be a bit canny about how I arranged my weights so that I was not twisted to one side, but with identical 12 litre aluminium cylinders I noticed a slight pull to one side only when there was a 150 bar difference in remaining tank pressures.
When rigging two cylinders, stand them upright on a flat surface and, after slipping the wetted bands over them, progressively tighten each side until maximum torque is achieved. After that, even if dried out, the tanks stay secure all week.
The Blocks come in two sizes, to suit standard tall tanks or with curvature to suit squatter ÒdumpyÓ tanks. They take up little space in your luggage and their weight is of little consequence. You will need to take the extra regulator, however!
Buddy Twinning Bands and Blocks cost £39.
AP Valves 01326 561040, www.apvalves.com
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+ Lightweight take-anywhere solution to twinning cylinders
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- May not be ideal for use with manifolds
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I have received some criticism of late. So what's new? This time it has come from those who think I miss out an important fact when I write about any dive bags I have used - namely, the actual unloaded weight of the bag.
This can be crucial to those travelling with a restricted weight allowance. For example, the best bag I possess, judged on its ability to protect the contents, weighs 15kg empty. It's made of robust polycarbonate, rigid enough to take any amount of knocks yet keep the contents safely cocooned within it.
However, this quality is reflected in the excess-baggage charges to which I am subjected when travelling with it.
I normally return the equipment sent for test to the supplier. Bags are another matter, because they are not always handled by people who feel they should be looked after.
When a company sends a bag for test, it doesn't expect to be able to sell it afterwards, as some suppliers do with other items of gear submitted for test. So at any given time I have a number of bags in various states of destruction.
A quick examination of these reveals that most weigh in at 4-5kg. These big bags with extending handles and wheels will take all my dive kit and more, plus clothes for a typical trip. I include the products of Stahlsac, Tribord and IQ in this line-up.
With the mean-minded baggage allowance of 20kg typical on inter-European flights (now often 25-30kg on charters arranged by those selling diving holidays) such a weight makes a dent before you even start packing.
I have never had contents broken while using any of these bags, because they use robust materials, but they all get ripped or torn eventually. It depends how many trips you expect such a bag to make, and I make more than most.
A reader wrote to me full of praise for the bags made by Quba Sails. Aimed originally at the sailing fraternity, they are made from sail-cloth - perhaps even cloth from sails that no longer make the grade for their original use.
Quba sent me a Large Bag to try and it weighed less than 1.5kg. That's light. It's made in the same way that sails are made, with broad stitching.
Its massive nylon zip is closed by a stainless-steel ring-pull of the sort you might expect to see on yachting equipment, but it has no other features to mention. Its capacity is as big as that of any of those dive-bags I have tested, but what it seems best suited for is carrying sails. I don't know how it would withstand the wear and tear once loaded with the rather heavier items that we divers tend to transport, and I was reluctant to give it a try.
My last trip involved checking-in my bag to be sent to its final destination via two other airports. In the event, it arrived slightly the worse for wear one day late, stickers revealing that it had taken in three unexpected airports around Europe.
I wonder how the Quba bag would have stood up to all that baggage-handling. I had loaded it ready for my departure, but at the last moment decided to change back to one of the typical bags I knew would stand up to the journey. So this was not so much a test of the Quba bag as of my confidence in it - and that confidence just wasn't there.
Call me old-fashioned, but I find it really boring to discover that I am in a distant country with some item of kit missing, and unable to do what I went there for.
Not only that, but once I had loaded it with more than 20kg, I had to carry it. My arms are long enough, and I don't need my knuckles dragging on the ground when I walk, so carrying as opposed to wheeling a bag has become a definite no-no for me.
I've seen people dragging heavy bags across airport floors. No doubt they wonder why the bottom drops out prematurely.
However, if you are young and strong, not prepared to pay excess charges to transport a heavier bag and willing to take a risk, this could be a useful bag for you.
The Quba Large Bag is not cheap. It costs £76.55.
Quba Sails 0870 777 1651, www.quba.com
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- You have to carry it
- Leaves contents vulnerable to knocks
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DIVE SLATE
What, I was asked recently by a journalist, is the greatest danger faced by a diver? Is it being entangled in kelp or attacked by a shark? He either hadn't seen the film Open Water or hadn't taken it seriously, because I surprised him by saying that being left at the surface was probably the greatest hazard. Recent events in the news have borne this out.
One winter, years ago, I went out diving in Majorca with a girlfriend. We had a lot of mechanical problems with our boat and, although the weather was foul and the boat out of action, we were still determined to get under water. So we persuaded a local fisherman to take us out in his little wooden boat.
The Mediterranean Sea is a challenging place when the sky is black with rain, the water grey and heaving, and the wind blowing remorselessly. Ours was the only boat on the ocean, but often the diving is at its best under these circumstances and we were not disappointed at the remote tip of Isla Dragonera.
Before we dropped over the side, I explained in my not-very-coherent Spanish that we would resurface in exactly 40 minutes and the boat should be there when we came up. It was not.
It's at this point that one starts having regrets. Had the fisherman fully understood the plan? Had he gone off fishing for the day? Did he even have a watch? Were we going to have to make the four-mile swim in turbulent waters back to land?
After 10 minutes, the little boat reappeared and we climbed gratefully aboard. We had been using precise northern European time, whereas he had been using Majorcan fisherman's time - a much more relaxed method of time-keeping. However, it served to remind me of how much we need to be able to trust those in charge of the boat that provides our surface cover.
When you gleefully jump into the water from a boat, how often do you question whether anyone will be there to pick you up? It would have been unforgivable if our fisherman had forgotten us, but what about those big liveaboards where the passengers don't know each other and the diver accounting system may not be that great? Ever thought of supplying your own?
That's what the guys from British Divers Manufacturing decided to do. They have come up with an individual diver's tally that you give to your boat cox'n or dive marshal before you start your dive. It's called the Dive Marshall. I guess the spelling is related to the name of its inventor - or was the idea perhaps conceived at Bikini Atoll in the Marshall Islands?
It's a heavy engraved stainless-steel plate, reminiscent of a US Marshal's badge, with its own neoprene pouch attached by a lanyard. It also has a pencil attached by a second and separate lanyard. There are roughened areas on which you can write your own and your buddy's names, and details of your dive plan.
Most importantly, part of the writing area is designated for the planned dive time, and this is below a small Casio digital timer that is firmly attached to the metal.
You set this timer going on leaving the boat, and the fact that the tally remains with those aboard tells them that you are still diving. A simple comparison of the planned dive time with the elapsed time tells them how overdue you might be. You can also add extra information, such as at the time-point in the dive at which you expect to send up a delayed SMB.
Of course an unscrupulous crewman, on finding that he had left you behind the day before, could lose the Dive Marshall and deny ever having been given it. Or reset the timer in your absence to cover any negligence or forgetfulness. So this idea will work only with the co-operation of those covering for you. Still, if it makes their life easier, I'm sure they will take to it.
On the initial examples sent for me to try, the roughened area for the writing made erasing it afterwards difficult. The final product has a far better finish and I found it easy to remove my writing by dabbing it with Blu-Tack (not supplied). There's also an area on the reverse that allows you to re-sharpen the pencil, a feature I found very necessary.
With the pencil securely attached to the slate as designed, the stop/start button of the timer is covered. I guess one could accidentally reset the timer to zero during handling, though the button is recessed to stop that happening.
The Dive Marshall comes in three colours, to help you pick out yours if travelling with other similarly equipped divers.
It's not cheap, but it should last a long time, as it's made of 316 marine-grade stainless steel. The timer should put up with the wet conditions found on some boats because it is depth-rated to 50m. The manufacturer claims that test examples survived being thrown from aircraft (presumably in flight), dragged behind a speeding RIB, frozen in a block of ice, and repeatedly run over by a Land Rover.
Well, that should cover the worst excesses of the way I treat my diving equipment in a typical day!
The Dive Marshall costs £49.50
British Divers Manufacturing, www.britishdiversmanufacturing.co.uk
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+ A good safety-tool when used properly
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The slates come in several colours to make them more readily identifiable
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