Step into any specialty area, diving or non, business or pleasure, and you will come across buzz-words, acronyms, abbreviations, and other odd terminology. Underwater photography is no different. If you are going to get into underwater photography, it is helpful to know some of these terms and buzz words before you venture forth shopping or in conversation with aficionados that have been at it for awhile. For sake of space, I will not spend a lot of time on terminology common to photography, but to those terms that pertain to underwater photography in particular, and no doubt I will miss some.
MACRO vs. WIDE-ANGLE
The job of the lens on a camera is to gather the image in a sharp form and convey it to the film or digital input device. What kind of lens you put on the camera will impart images in different ways. For land cameras, most choose a zoom lens that offers a variety, all in one lens.
With most consumer cameras 50 or 55 mm is a “normal” lens (not to be confused with the term “35 mm camera,” which refers to film size). With a “normal lens” the image you get is roughly equivalent to what your eye sees — no magnification, no reduction. A “wide-angle” lens shrinks the image and takes in more of the view. With film cameras, a lens rated 40mm or smaller are considered “wide-angle.” For underwater 28 mm is good but 20 to 15mm is even better. The main advantage of a wide-angle lens underwater is you can get very close to your subject (minimizing the negative effect of a lot of water between the camera and your subject) and the deep range of focus (depth of field) in wide-angle lenses.
“Macro” refers to extreme close-up photography (two feet or less, usually only inches). Although extreme close-up is possible with a wide-angle lens, macro lenses (or similar set-ups) are for detailed views of small animals at some degree of magnification.
AMPHIBIOUS vs. HOUSED
Cameras underwater fall into one of two categories: amphibious or housed. An amphibious camera is specifically meant to get wet and go underwater. Nikonos (now discontinued) and most of the Sea & Sea cameras are excellent examples of this kind of camera. Amphibious cameras are usually available as complete systems (strobes, arms, cords, etc.) and work well on land as well, although certainly not as well as land cameras.
Housed cameras are cameras that are made specifically for the use on the land, adapted for underwater use by placing them in water-tight “housing” that allows access to the camera through a variety of controls. In general, with a housed camera you must purchase the camera and housing separately, although many manufacturers of lower-cost point-and-shoot models will sell them as a package. With a housed camera you get the sophistication and features available for the most part only in surface cameras. Often the finest lenses are available only with a land camera. With the more sophisticated land cameras, the housings add size, bulk and weight.
PORT
If you are using a housed camera that can accommodate interchangeable lenses, it is rare that the front portion of the housing, the “port,” will fit all lenses. On most high-end housings, this section of the housing is interchangeable to accommodate specialized lenses. You will usually have to have a wide-angle “dome” port and a tube shaped macro port. These ports are important considerations when you realize that they can add hundreds to the cost of a housing system.
STROBE
It’s dark underwater and cameras don’t like that. To make colors and textures stand out you need artificial light. This comes in the form of an underwater flash unit usually known as the strobe. From a battery source a capacitor is charged to hold a high amount of power that is rapidly release as the flash. It puts a high amount of light in one spot at one time.
GUIDE NUMBER
This is the power rating number for the strobe. The higher the number, the more powerful the strobe. But make sure you are comparing apples to apples in that the numbers you are comparing are at the same ASA rating.
STROBE ANGLE
Strobe angle is the beam width of the strobe. This is especially important for wide-angle photography.
RECYCLE TIME
Strobes take time to recharge between full power firings — 2 to 8 seconds depending on the model and power setting. This is important for cameras with motor drives or digital cameras that can rapid fire images.
COLOR TEMPERATURE
The color quality of the output of a strobe is referred to as color temperature. Most are set at color equivalent to daylight, but some have a slightly warm cast to compensate for the blue cast that water can impart.
ARMS
Mounting strobes to the camera is done with strobe arms. The arms allow you necessary flexibility to position strobes to direct light into the desired locations.
TRAY
Foundational support for the extras of strobes and arms and sometimes other items is the tray. Many housed cameras have a tray built in, but most amphibious cameras do not, although many are sold as part of a package.
