Monthly Archives: August 2016

  • Talk About Tank Valves!

    We divers are creatures of habit. We like to do things the way we always have. Instructors who teach their trainees exactly what their instructor taught them exacerbate these habits. Outdated techniques and theories are handed down like gospels. Sometimes, a better way presents itself, but there is often a reluctance to step off the well-trodden path into the undergrowth of a new experience.

    Take the tank valve. It’s like a water tap. ‘It’s lefty loosey, righty tighty.’ One shouldn’t need to know more than that. However, with a tank valve, you’ll want it either fully open or fully closed. This is where old habits can interfere with good practice.

    Back in the day, tank valves could jam if they were opened too far. Older divers were taught to open the valve all the way and then close it a quarter of a turn. All well and good if you are precise in your habits, but what of the diver who does that and then forgets he’s opened the tank and closes it by mistake, turning it back open a quarter of a turn? His air supply will be uninterrupted at the surface, but as he goes deeper, it will become harder and harder to breathe. If he’s lucky, he’ll see his pressure gauge drop to zero on each inhalation before returning to the full-tank position. If he’s unlucky…well?

    Today’s tank valves don’t jam in the open position, so open the tank all the way and leave it there. When you want to shut off the gas, close it all the way. No half-measures, no quarter turns, and you’ll stay safe.

    If you are using higher percentages of oxygen, you should know to open a tank valve cautiously, especially the O2 tank on a rebreather. A sudden rush of oxygen could cause a fire.

    Also, do you give your regulator dust cap a blast of air to dry it after a dive? That’s no better at removing water than using a towel, and it is exponentially noisier and can be harmful to the well-being of a person standing nearby, by startling them. Furthermore, that blast may actually drive water droplets into the uncovered first-stage of a regulator -- now you have to service it -- or dislodge the O-ring of a tank suitable for use with an international A-clamp. Using a towel can save you from scrambling around your dive boat, looking for that missing O-ring.

    These outdated habits regarding tank valves simply refuse to die. Changing the habit of a lifetime can save your reputation as a serious diver, maybe even save your life.

     

     

     

     

     

     

     

  • Electronic Flash (Strobe) or Video Light?

    Photography techniques continually evolve. Back in the ‘sixties when I first started life as a photographer, lighting for photography was directly developed from lighting for movies. Huge spotlights of 2000 watts and more were called ‘brutes’ because they could really hurt you. Smaller ones were called ‘pups’. Little 500 watt spots were called ‘inky-dinkies’ because they produced so little light. Camera exposures were long, in the order of a second or more. Live subjects had to keep very still.

    Lighting men wore heavy gloves and needed to be very muscular. The lights themselves produced a huge amount of heat, which meant ramifications, especially with food photography because the subject would literally cook under the lights. Enterprising photographers got round this by substituting mashed potatoes for ice cream, painted ball bearings for peas, and so on. No wonder the contents of food packaging never looked like what was shown on the label!

    Flash was limited to expendable flashbulbs, some as big as household bulbs, which came at a cost. Then reliable electronic flash was invented and the likes of David Bailey and modern photographers of the ’sixties never looked back. Of course, it needed a lot of skill to use because you could not see what you were getting until the film was processed.

    This was paralleled in the underwater photography world. Pioneers used big flashbulbs because the batteries needed to fuel big constant light sources were impractical.

    Eventually, underwater electronic flashguns (sometimes called strobes) became reliable and small enough not to encumber a diver already with a big camera. Electronic flash became ‘de rigeur’ for underwater still photography. Shooting video was different. You needed a constant light output.

    Bulb and battery technology was such that as recently as 1992, I was taking a video rig into the water that weighed more than 100kg thanks to the huge ni-cad batteries for the lights. It often had to be derrick’d into the water. Even so, the lights were not bright enough to be effective over more than 75cm distant and totalled only 400 watts.

    bigblue_big_2Times change and technology develops. Today you can buy a 15,000 lumen LED light that weighs less than a kilo including its battery. At the same time, underwater electronic flash (strobe) has become quite tiny compared to its light output. Obviously, you need a constant light source for recording live-action, but which is better to use for still pictures?

    Well, we don’t have to wait for our film to be processed to see results thanks to digital technology. The results appear instantly on the LCD screen of the camera the moment an exposure is made. So what are the differences?

    Electronic flash, even in a small package, can deliver a very high output, more even than that 15000 lumen light, in a very fast burst, freezing the action. A set of four small batteries with last for hundreds of exposures.inon_s2000_1

    However, you need to have some idea of what you are doing. This comes with practice because you cannot see the effect before you press the camera’s button. You need to spend a little time familiarising yourself with the controls. You need to take at least one shot to be sure of what you are getting.

    Some electronic flashguns have aiming light built in. These are only good for telling you where they are pointed during a night dive. They cannot be a substitute for a dive light. sea_sea_ysd2_1To help a camera focus on macro subjects, often it’s a good idea to employ a separate aiming light mounted on top of the camera. These can have an auto-flash-off function so that there is no annoying spot of light added to your pictures. They can also have a red light mode so that marine life is not aware of your light at night and you can ambush it with the pulse of white light from your flash.bigblue_blackmolly2_1

    A video light is a constant light source and can double as a dive light although since the spread is so wide and even, it will not be very penetrative like a purpose-designed diving light.

    When lighting a subject for the camera you can see its effect before taking the picture but it will not give you such a small working exposure as a flash and less depth-of-field (focus). It can also be difficult to get close to marine life because the light might scare it, and you will need to get close for it to be effective. Of course, a constant light source (video light) can be used to live action as well as still pictures and its controls will be easy to understand.

    idas_venom38_1Don’t expect a video light to be less expensive than a flashgun (strobe) either. By the time you’ve mounted it on the camera, the cost will be around the same.

    So which is best for your needs? A flashgun or a video light? There is now one solution available that combines both. The iDivesite SS-1 Symbiosis and the doubly powerful SS-2 Symbiosis each combine a 2000 lumen video light with an electronic flashgun (strobe), powering both from the same rechargeable battery.i-divesite_symbiosis_ss2_b

     

     

     

     

     

     

     

2 Item(s)

Our Brands