Monthly Archives: April 2015

  • Lighting Underwater Pictures

     

    Flashguns mounted on long mounting arms. Underwater photography requires special considerations and it's best to read a book on the subject before you jump in!
    How often do we hear divers, ecstatic after coming back from a dive and describing the visibility as being ‘gin-clear’? The horizontal visibility might have been exceptional and offered clear vision for thirty-metres. Great! How often do we hear of fog warnings on major roads with visibility reduced to thirty-metres? That sums up the difference between being in air and being under water. Water is full of detritus, tiny planktonic life-forms, and other contents for the ‘soup’ in which we normally dive. Not only that but natural daylight from above tends to be flat and dull. Yet when you look at pictures in diving magazines that are crisp and there is usually no hint of this poorer visibility. The photographs look sharp and clear. Why is that?
    The author's lighting rig. (Picture by Ivan Petrov) The author's lighting rig. (Picture by Ivan Petrov)
    Well, your pictures can be equally crisp once you have an understanding of the limitations imposed by making them water. The same rules apply whether you are using flash to shoot still photographs or a continuous light source to shoot moving images. The first rule is to get as close to your subject as possible, eliminating as much of that water as you can. This is where a wide-angle lens, a fish-eye lens or a macro lens can help. The second rule is to light your subject with a full spectrum of colour and that normally needs to be supplied by a light or strobe (electronic flash) that you take with you. You will need to be sure that the light coverage of that light source is adequate for the lens you are using. Plastic diffusers fitted over the front of the light ensures an even wide-angle of light output. Although many underwater photographers opt for two flashguns to give them even lighting, a thoughtfully positioned single flashgun with such a diffuser will usually give just as pleasing results. Some subjects such as sharks actually benefit from the added contrast of a solitary light source.
    A hawksbill turtle feeding on soft coral and photographed by a solitary flash. A hawksbill turtle feeding on soft coral and photographed by a solitary flash.
    How you position this ancillary light is crucial and at Ocean Leisure we can supply you with all manner of problem-solving devices in order to mount your lighting to your camera rig. The major difficulty that people encounter is inadvertently lighting up this detritus in the water. We call it ‘back-scatter’. There are two basic philosophies to how you might position your lights. I subscribe to a solution that positions my light or light as far away from the lens axis of the camera as possible. Imagine if you will, your light or lights illuminating a cone of detritus directly in front of them for a distance of, say, thirty centimetres. You need to be sure that these cones of back-scatter do not intrude into your picture area. This means that with a wide-angle or fish-eye lens you need to get them as far from the lens as possible. I use long flash-mounting arms, angled in such a way that the light sources are not ahead of the lens. They are angled slightly backwards but I can point the flash heads back directly at the subject and get the full effect of the light emitted. An alternative philosophy is to angle your flash heads in such a way that the cone of back-scatter is angled out of the picture. Lighting cameramen in the movie industry call this ‘edge-lighting.’ You use the edge of the light and that reflected off the back-scatter in the ‘cone of light’ adds to the amount of light arriving at the subject. This allows you to use shorter flash-mounting arms with the added convenience that brings with it, but reduces the amount of light illuminating your subject. The standard one-inch ball and clamp systems effect many different solutions.
    My flashguns are mounted on the long arms that ensure they are far from the lens axis of the camera. My flashguns are mounted on the long arms that ensure they are far from the lens axis of the camera. (picture by Saeed Rashid)
    Be coincidence, Saeed Rashid and I both photographed a turtle at the same time and each shot reveals the two alternative ways to light a subject. His flashguns are angled outwards for ‘edge lighting’ whilst mine are angled for a direct effect. The choice is yours but Ocean Leisure has a large stock of mounting arms and trays by a range of different manufacturers.
    Saeed Rashid angles his lights outwards a little in a semblance of 'edge lighting'. Saeed Rashid angles his lights outwards in a semblance of 'edge lighting'. (picture by John Bantin)
  • Nitrox - All You Needed To Know

    Know what you breathe before you take that plunge! Know what you breathe before you take that plunge!
    What is Nitrox? Air is mainly made up of two gases – 21% oxygen and 78% nitrogen (1% other gases). We metabolise some oxygen in the air we breathe but the greater part, the nitrogen, is inert. When we put ourselves under pressure, as we do when we go under water, our bodies absorb some of this inert nitrogen. As we go deeper and stay longer we absorb more. The time that we spend underwater is limited by the amount of that nitrogen we absorb. That is why we used to use tables or, more recently, a diving-computer. So why not breathe an air that has less inert nitrogen gas and so reduce the problem? If you’ve been breathing air, you’ve already been breathing nitrox – nitrox21. Other nitrox mixes have the percentage of oxygen increased and therefore the percentage of nitrogen is decreased. Nitrox 32 has 32% oxygen and nitrox36 has 36% oxygen.Nitrox Diving Breathing a richer nitrox mix instead of plain old air reduces the chance of decompression illness due to a diver staying down too long or coming up too quickly - providing no-stop times and ascent-rates for air are adhered to. If you want to continue with conventional levels of caution you can simply adjust your decompression requirement by adjusting your computer to match the nitrox mix you use and in that way get more time underwater.Scuba Jump However oxygen too has its problems too. Pure oxygen becomes poisonous at quite low pressures. It is currently thought unsafe to breathe pure oxygen at a greater pressure than 1.6 bars underwater and that occurs at only 6m deep. Therefore each specific nitrox mix has its own maximum operating depth and nitrox training agencies are unanimous in limiting the use of oxygen to 1.4bars of partial pressure within a mix with nitrogen._DSC0019 What you need to know is that the oxygen in air (nitrox21) can become hazardous at 54m deep. That does not affect leisure divers limited to an absolute maximum depth of 40m. A standard mix of nitrox32 should not be breathed deeper than 32m. Some training agencies tells new divers that this limit is 30m. Most popular sites for diving in the world now adhere to a 30m limit for leisure diving anyway. PADI Open Water Divers with Level One training are still limited to a maximum depth of 18m during training as before but suitably qualified divers can use nitrox32 to its full maximum operating depth (MOD).
    No additional equipment is need in the water. No additional equipment is need in the water.
    So for nitrox mixes up to 40% oxygen, no additional diving equipment is needed, only the knowledge of how to analyse the contents of a tank before diving, using the analyser supplied by the dive-centre and knowing how to set your computer to match. The day is foreseen when all new divers will start off breathing nitrox and air for diving will only be for specialised uses. More advanced divers that have been deeper than normal leisure diving depths use nitrox to speed up their decompression.
    Using a richer Nitrox in an additional tank to speed up decompression after a deep dive. Using a richer Nitrox in an additional tank to speed up decompression after a deep dive.
    They take additional tanks of rich nitrox with them and swap to these once they have ascended shallow enough for it to be safe do so. There are more advanced diving computers that allow you to set different levels of nitrox and to switch to the one that matches the actual mix the diver is currently breathing, and in that way track both decompression requirements and oxygen exposure accurately. All the diving computers sold at Ocean Leisure are nitrox compatible. If you want to know how to take high-speed sequences of pictures or successfully take photographs underwater, ask the guys at Ocean Leisure Cameras.

  • What's a Reef Hook For?

    We recently received a FaceBook message from a very happy customer to Ocean Leisure, who told us what a godsend the reef hook we had suggested was. He had called by on his way to the Sudan and equipped himself with all the underwater photography equipment he needed as well as a lot of new scuba diving equipment. As usual we asked him where he was going and on hearing that he was joining a member of the Cousteau family on a trip we suggested he took with him a reef hook.

    A Reef hook with braided line and clip.
    The water that forces itself over the deep water tongues of each reef in the Sudan can be forced to speed up just as the air over the top of an aircraft's wing has to increase its velocity resulting in often strong currents. Places like Sha'ab Rumi are famous for this phenomenon and that is what encourages the sharks. Requiem sharks need forward motion to force water through their gills in order to breathe. If they find a place with a strong current, they can relax in the flow letting the forces of nature do the work for them. It's not unique to the Sudan. Water forces its  way into the channels of the Maldives, through the passes of the Tua Motos in French Polynesia and between the islands of Indonesia as tidal differences in the ocean affect the height of the water within the lagoons of atolls of the water levels in the minor seas to the north of the Indonesian archipelago. Among many other places, Palau has some powerful current points like that at Pelelui Cut and Blue Corner too. We should not forget the diver's flavour-of-the-year, the Dampier Strait in Raja Ampat, either.
    Grey Reef Shark in the Maldives Grey Reef Shark in the Maldives
    It can make scuba diving arduous but many divers think it's worth the effort. Why? Because once you have swum down and located yourself at the point on the reef wall where the action is to be found, you merely need to cling on and watch the show. Of course, clinging on to a coral reef is to be discouraged thanks to the damage it does. Even if you were able to cling on to bare rock as one can in the waters of Cocos or the Galapagos, you'd need a strong pair of leather gloves if your hands are not to be torn. Gloves more often used by sailors are appropriate. Neoprene diving gloves get ripped to pieces within a few dives.
    Enjoying a strong current at Rangiroa in French Polynesia. Enjoying a strong current at Rangiroa in French Polynesia.
    Better still, why not avoiding touching any surface altogether? That's where the reef hook comes into its own. You simply hook in to a suitable area of rocky substrate and allow yourself to be pushed back by the flow of water. The reef hook is at the end of a length of line that is hooked to a strong part of your BC such as a suitable stainless steel D-ring. A little bit of air added to the BC gives to enough buoyancy to fly like a kite above the reef and you hover there comfortably while you watch the sharks and other fishes putting on a show.
    Flying like a kite with a reef hook to enjoy diving in a channel in the Maldives. Using a reef hook to enjoy diving in a channel in the Maldives.
    When it comes to time to go, you simply pull yourself down the comfortably braided line and unhook, not forgetting to dump that buoyancy air from your BC before you are swept back into the channel behind you or into the lee of the reef. A reef hook is an inexpensive item of kit that is stowed in a BC pocket forgotten until you need it. If you are going anywhere that currents are featured, we certainly recommend it. If you've enjoyed reading these blogs, you will enjoy reading Amazing Diving Stories by the same author.

  • The Joys of the Bahamas

    The Bahamas are only a single flight away from the UK and represent some fabulous scuba diving and snorkelling opportunities. Even if you are a non-swimmer you can experience its underwater world courtesy of a bubble-sub operated by centres on New Providence, the home to the capital of the Bahamas, Nassau.

    Enjoying a ride in a Bubblesub. Enjoying a ride in a Bubblesub.
    The Bahamas are famous among divers for its shark-feeding dives, where diver can get close-up and personal with its Caribbean reef sharks. Diver's are never in any danger and he sharks are only turn up for the free hand-out of food offered. It's an educational experience when you discover that these are not the undiscerning and voracious predators so often portrayed by the sensation-seeking media. In fact thousands of divers have attended these shark feeds near New Providence without anyone being injured although more experienced divers are now visiting other parts of the archipelago in a quest for greater thrills with tiger sharks and oceanic white-tips.
    Caribbean reef sharks pass close by divers in the Bahamas and yet nobody feels in the leas bit threatened by them Caribbean reef sharks pass close by divers in the Bahamas and yet nobody feels in the leas bit threatened by them
    Divers are fully briefed before they enter the water where they take up position as instructed and wait for the shark feeder to arrive with a box full of bait. The sharks are used to this and will follow the feeder rather like a flock of over-sized pigeons. Once the feed begins the sharks circle round in an orderly manner while the feeder passes out cuts of fish on the end of a short spear. The sharks are careful not to get in each others' way and subscribe to a definite order of priority. While they are circling in this way it makes for a great photo-opportunity.
    Cave Diving within a Blue Hole
    If you really want to seek out hazardous circumstances under water, the islands of the Bahamas are riddled with prehistoric cave systems that flooded once sea levels rose after the last Ice Age and these tidal caves so formed (often called Blue Holes) can represent some of the toughest diving conditions in the world and are only suitable for visits by carefully trained cave divers. However, on the island of Grand Bahama it is possible to get a carefully supervised introduction to this sort of experience. You'll need plenty of reliable lighting equipment and we can help with that at Ocean Leisure. Notwithstanding that, there are plenty of other great scuba diving opportunities in the waters of the Bahamas. Many of the reefs are still in pristine condition and make for very pretty dives.
    Theo's wreck off Grand Bahama Theo's wreck off Grand Bahama
    The outer islands have immaculate conditions with reefs heavily populated with fishes while around New Providence and Grand Bahama there is a plethora of shipwrecks waiting to be visited. Most of them have been intentionally sunk for the benefit of divers ad some of them have been used as underwater sets for famous Hollywood films. Sanctuary Bay on Grand Bahama is home to a colony of dolphins that have been rescued from circuses and dolphinarium throughout the world. You can pay for a dolphin experience and go out to see with one of these human-friendly mammals.  You pend around forty-five minutes in the company of the best breath-hold diver you will ever encounter. On your part, it's breath-taking!  You would certainly regret not taking a camera with you to record the experience.
    A human-friendly dolphin from Sanctuary Bay, Grand Bahama. A human-friendly dolphin from Sanctuary Bay, Grand Bahama.
    These are Atlantic bottlenose dolphin and they represent very big animals. It'd amazing to watch how effortlessly they can move in their home environment yet they are never tempted to stray from home because they are regularly fed there and are clever to know a good thing when they see it. What do you do in the Bahamas when you are not underwater? Did we mention the warm sunshine, the fabulous food, the white sandy beaches, the clear turquoise water and the friendly people? Remember to get your diving equipment serviced in good time before you make any dive trip.
    Did we mention the turquoise water and the friendly people? Did we mention the warm sunshine, the clear turquoise water and the friendly people?
     

  • Vacuum Leak Tests

    Photographing a Dugong in Egypt The Author photographing a Dugong in Egypt
    In a career as an underwater photojournalist spanning twenty-one years I made around three-hundred individual dive trips. That amounts to more than six-and-a-half -thousand dives and virtually every one was made armed with a camera. Would it surprise you to know that in the process I flooded a couple? Well, you might think that two floods in that many dives is not a bad average but I can tell you that every one left me cringing. It’s not just the cost of replacing the camera but it’s the cost of missing out on the pictures while you are so disarmed. How do floods occur? Inevitably it’s a case of user error. All you need is a badly seated main O-ring or some foreign body to drop on to it just as you close up the housing and it’s “Goodnight, Nurse!” Putting the camera into its housing after reloading a freshly charged battery of a new memory card should be straightforward. It is if you are in a clean environment such as a well-lit hotel room and nobody distracts you while you do it. However the world is not a perfect place and substitute those idyllically serene conditions for the rolling deck of a dive boat in a rough sea or the gloomy interior of an island hut and operational accidents can happen. Some people take their housings into the sea for a first dive without their camera installed. I see little point in this since the housing must be cracked open in order to install the camera later and that is when O-rings might pop unobserved or  a stray strand your girlfriend’s hair might float into the place where it can cause chaos. As a busy professional, I always carried a duplicate camera and lens with me in case the worst happened. I might see tell-tale bubbles escaping from the housing while underwater and lose a dive but at least I could carry on afterwards. To flood two cameras on the same trip is tantamount to carelessness.
    The author photographing a Great Hammerhead (Picture by Bob Semple) The Author photographing a Great Hammerhead shark (Picture by Bob Semple)
    With a little compact camera in a transparent plastic housing you can always check for a leak by gingerly immersing it in the fresh water rinse tank. The sight of a few drops of water that can be removed before they do any real damage will reveal a leak. Not only that but a cursory examination of the O-ring in its groove through the transparent plastic will show up any break in the watertight seal. Not so with machined aluminium housings. One just had to be fastidious in preparation and have faith in your ability to do it right. A leak detector merely sets off a loud siren should it detect water inside the housing. By then it is usually too late and only adds more crisis to the drama as you try to get back to the surface before the precious camera inside is lost for good.
    Leaksentinel unit Nauticam Vacuum Valve
    Gradually I evolved from shooting on 35mm film to digital cameras and from there inevitably ended up working with full-frame DSLR cameras. These became so expensive to buy that there was no way I could warrant the expense of doubling up but technology came to my rescue in the form of the vacuum leak-test.
    Nauticam Leak Detector In Use Pumping out the Air from the Housing
    Instead of testing for leaks with water that will ruin the camera should you get it wrong, you test for leaks prior to diving using non-destructive air. This is by and large how they work although different makes of equipment have intermediate lights using different strategies. After sealing up the housing with the interior full of air at ambient pressure, a warning light indicates that. It is red. You then pump out the interior through a special valve in the bulkhead of the housing using the pump supplied. Once the interior pressure-sensor determines that a suitably low pressure has been reached, the indicator light shows green. Green is good.
    Nauticam traffic lights Indicator Lights. Green is Good, Red is Bad!
    Leave the housing for at least twenty minutes. If any air leaks back in, the warning light changes to red. Red is bad. If that happens you should reopen the housing and see what is amiss. It’s not a test of the housing. It’s a test of how well you closed it up after installing the camera. During the last seven or so years that I had the benefit of the vacuum leak test on my camera housing, I never lost a camera. Twice in that time I got a red light but was able to rectify the problem before it was too late. In previous years I would only have discovered the fault once I was under water with depressing results.
    Leaksentinel by Vivid Housings Sentinel Vacuum Leak Test
    I recommend anyone with a valuable camera to get the advantage of a vacuum leak test installed. Both Hugyfot and Nauticam, makers of camera housings, can supply them although it is an extra cost with Nauticam. There is also and after-market version called the Leak Sentinel that can be fitted to a wide range of housings. I can confirm that I always slept well in my cabin or hotel room while that little green light winked all night but I woke up with a start both times a red light began to flash. Green is good. A by-product of depressurising the housing is that the fittings are pulled tight and it is impossible to open unless you purposefully release the air-input valve. This means that both lens port and back are secure from accidental opening, for example in the fresh-water rinse tank, the site of many an accidental flood. I recommend you get a housing with a vacuum leak test or get one fitted and be released from the stress of waiting for a flood. After all, the saying goes, it’s not ‘if’ but ‘when’. John Bantin is the author of Amazing Diving Stories.

  • Our Colourful World Underwater

    If you read the last blog about the physics of underwater photography you will understand why everything can look monochromatic underwater, once you have moved away from the surface. This can be misleading and often the new diver’s first introduction to the colour of our underwater world is during his or her first night dive.

    Soft corals in the Maldives (Vilamendhoo).
    Without the blue of the daylight swamping the true colours of the reef, the diver’s underwater light illuminates everything in its true colours – and what a colourful world it is! It’s for this reason that experienced divers are often seen going into the water with powerful lights or torches even on the most brightly lit days. By taking a bright white light close to a subject, it’s revealed in its true kaleidoscope of tints. However, at night you’ll see the fishes in their night-clothes (so to speak) because often the colours they exhibit in daylight are different to those in the dark.
    Coral trout on a sponge encrusted wreck.
    It’s amazing how much marine animal life is actually bright red when you consider that red looks black to most marine life. Nobody can really explain the reasoning but it’s true. Often, fishes that may appear a dirty green colour by natural light are revealed to be bright scarlet in the beam of a lamp. Underwater photographers can take advantage of this phenomenon by lighting up their subjects with an underwater flashgun or strobe light while those shooting live action can employ powerful video lights to the same effect.
    Anemone fish in a purple anemone.
    Even the smallest subjects can be revealed in a startling vividness once they are subjected to a full spectrum of light. Sharks may be the guys in the grey suits, along with many other predatory pelagic species, but once you look closely at any territorial animal with the aid of your diver’s torch, you can appreciate the full range of hues that they wear.
    A wreckfish in the wreck of the Chikusen, BVI.
    Big grouper suddenly appear to be much prettier than their otherwise brutish look might signify.
    Green turtle feeding on seagrass (Egyptian Red Sea)
    Even green turtles can be revealed as more colourful than you would expect. You would not contemplate entering a dark wreck without a lamp to guide your way (and possibly a second one stowed about your person as a back-up should the battery in your primary lamp inexplicably fail). That may seem obvious but even rusty shipwrecks and their cargoes can be quite colourful beyond the range of the oxidising metal because they get encrusted with tiny sponges and hydroids that give them colour. It's a colourful world.
    Inside the Rio de Janeiro Maru, Truk Lagoon.
    As for soft corals, these colonies of animals blossom in a strong current and display themselves in a wide range of reds, oranges, yellows, purples and blues. Going diving on a tropical coral reef without the aid of a lamp is rather like turning down the colour on your television set and watching everything in black-and-white.
    The wreck of the Bianca C in Grenada.
    Get yourself a good diving lamp and a back-up if you are diving at night or in wrecks and if you are shooting pictures, the people in Ocean Leisure Cameras, the store within the store, can fix you up with the appropriate lighting array. Come in and discuss it with them. The store is open seven days each week. Take a suitable light with you when scuba diving  and reveal the colourful underwater world. If you've enjoyed reading these blogs, you will enjoy reading Amazing Diving Stories by the same author.

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