Sabtu, 25 April 2009

Equipment for Cave Photography

Other desirable features on a cave camera include a wide angle lens, and the ability to focus manually. Digitals typically have a maximum angle from 28mm to 38mm. Wider angles (e.g., 28 mm) allow more flexibility underground, because the nature of the cave often dictates how far away you can get from your subject (there may be a wall or a gaping abyss behind you). Manual focus is important because many cameras simply won’t autofocus in the darkness of a cave. In show caves, though, the installed lighting may be enough to allow an autofocus camera to work.
The vast majority of images in this book were taken with a Nikon Coolpix 5000 (5 mp) digital camera. It has a 28 mm lens, and an adapter to allow a 19mm equivalent. Complete manual control was used every time.
Flash Units
Electronic flash units (strobes) are the bread-and-butter of cave photography. I typically carry four or more when shooting underground, ranging from very small to very powerful. The ideal flash unit is compact, powerful, has a manual fire switch, and capability to vary the output manually (i.e., to ½ power, ¼ power, etc.). Many flashes have both hotshoe and PC connections, one of which should work with your camera.
The lighting power of a flash is specified by its guide number (see sidebar), the higher the number the better. My favorite flashes, which meet all the above criteria, are the Vivitar 285, and the Sunpak 400 series, with a GN of about 80. By far the most versatile of flashes in the Sunpak 120J, which has a “bare-bulb” flash head with a reflector. Taking the reflector off gives a very broad range of illumination compared to the standard flashtube on most strobes.
To power electronic flashes, I recommend using rechargeable Nickel-metal hydride (Nimh) batteries. Get them in as high an amp-hour rating as you can find (2000 or higher in AA size). Not only are they better for the environment and less costly if you do lots of shooting, they also allow the strobes to recharge much more quickly than do alkaline cells.
Flashbulbs are not made any more, but are very useful for cave photography because of their high power and ability to spread light out over a wide area. They can also be used underwater, as in the various shots of the lakes in this book. Bulbs and the units to fire them can still be readily obtained on ebay or www.flashbulbs.com. Unlike electronic flash, bulbs can only be used once.
Slave units
As mentioned above, slave units can be attached to external flash units and triggered by a small flash on the camera. These units range from about $20 to $80. Many of the cheaper units are rather insensitive, and will only work if fairly close to, and in direct line of sight of, the trigger flash. Better units can respond to even reflected flash, and at great distances. The Wein Ultra-slave is rated by the manufacturer to respond to a flash 1500 feet away! Two highly sensitive slaves are manufactured specifically for cave photography: The Firefly Slave and the Gibson Slave.
Protecting your gear
If you only intend to shoot in show caves, gear protection involves little more than it does on the surface, such as a padded camera case. But shooting in undeveloped caves requires much more. They may be muddy and wet (as in the lower reaches of Black Chasm), and gear may have to be dragged through crawlways and pushed through small openings. I typically use waterproof plastic containers for my gear, such as the boxes made by Pelican and Otter. Less expensive options are Tupperware or other food containers. A bit of duct tape or stout rubber bands help ensure that the lid remains attached as they bounce around in a cave pack

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