Underwater Photography Tips :

How to Choose an Underwater Housing

     While most camera manufacturers do not offer underwater housing for their SLR or DSLR cameras (Canon does make underwater accessories for most PowerShot models), a variety of third-party companies do. Many of these speciality companies offer dedicated underwater housings, each with different specifications and capabilities depending on the camera they are designed for. Housings are generally constructed of acrylic or aluminum. The former are generally less expensive but are sometimes a little bulkier than their aluminum counterparts and may be a little less durable. Depending on your camera model, you may not have a choice but both materials are perfectly acceptable.

     A more important factor to consider is the depth rating. At best, if you take the housing deeper than it’s rated, the camera controls won’t work. At worst, the housing can leak or implode. Consider that, at the surface, air pressure is 14.7 psi (pounds per square inch). Pressure doubles at 33 feet underwater and increases by 14.7 psi for each additional 33 feet of depth. Dive to the bottom of a swimming pool to about 12 feet and you’ll feel the pressure difference in your ears. That gives you a hint about how much pressure your housing needs to withstand to operate at depth. If you’re only going to snorkel, you should be able to get away with a depth rating of about 33 feet (as long as you don’t do any deep free diving). Many DSLR housings have a depth rating of between 200-300 feet, which is deeper than most scuba divers dive but provides a good safety margin for the housing.

     After depth rating, perhaps the most important aspect to consider is which controls can be operated when the camera body is in the housing. Check out several different housings to see which one best meet your needs, especially if you plan to use many of the camera’s manual or advanced features. Get some hands-on time with the housing if you can or examine a diagram to see how the controls are positioned. You want control positioning that falls naturally within reach while your hands remain on the housing’s handles.

     With the advent of Live View, underwater photographers have another option for composing a shot. Keep in mind, though, that autofocus isn’t as fast with Live View but it does make for easier composing. If your camera is equipped with Live View, test it out to see whether it works for you. Otherwise, you can easily use the camera’s optical viewfinder. Although your eye is separated from the optical viewfinder by the housing and your mask, most housings come with a built-in optical system that provides increased eye relief. This magnification allows you to see the entire image in the viewfinder.

     You’ll also need to decide what type(s) of ports to purchase for your housing. Each manufacturer has slightly different specifications and provides a list that matches ports and lenses. Generally, though, you’ll need a dome port for wide angle lenses and a flat port for macro lenses.

Source : Canon.com