Watertighting: Key to Underwater Photography
Our World has been blessed with an abundance of life-supporting water. The wish to learn what lies underneath water surfaces is really ancient, but our ability to bring out the visuals from our “Inner Space” became possible only relatively recently.
Underwater housings are “air bubbles”
Our photographing devices are created for use in the air. All optical, mechanical and electrical components must have air around them to work properly. That’s why we encase a normal camera in an artificial “air bubble” and thus make sure it will operate in water. All underwater housings and bodies of amphibious cameras are just that: air bubbles for our everyday mechanisms, to work safely within.
There are ways to construct photo cameras impervious to both chemical and depth-pressure influence of waters. Instead of having air inside, these are filled with clear, electrically non-conductive fluid. This of course means that all the optical and mechanical elements have to be adapted to the new medium, but it is possible and such devices withstand all depths.
Types of underwater cameras
We use two main types of underwater photographing means, both becoming ever cheaper with some standardizations and mass production. While amphibious cameras can be used in the air and in the water, these seem the logical choice.
For now, the amphibians are somewhat depth-limited, usually to a maximum of -10 meters (33 feet) seawater. For SCUBA divers who normally go deeper, or for people who do not want to photograph underwater very often, the housing for their specific cameras may present a better solution. Whatever the urge and need, whatever kind of a camera has been decided upon, it’s “air bubble” has to remain safe and dependable.
In order to understand the watertighting, which is the most important feature of such cameras and housings, one has to know what a watertighting system does and how it should be maintained in proper working order. The drawings show how it works.
All cameras and u/w casings have to be opened to access some elements: batteries, contacts or memory cards. Their doors, covers and hatches must be opened and closed many times without compromising their ability to properly reseal the opening.
Manufacturers are trying to construct these accessing points as simple as possible for the user to operate, but some of those solutions are not as safe as can be for the innards of our air bubble! The extremely flimsy aprons, scratch-sensitive ridges and rubber covers are easily damaged.
Manufacturers that use O-ring sealings delegate some of the maintenance to the user, but also offer more safety to the cameras. Among all the watertighting means known, the O-ring principle works the best.
An O-ring is a self explaining name. It is made of perbunane, neoprene or silicon compound material, round in shape and also in cross-cut. The drawings show it as a fat black dot.
To work properly, the round O-ring has to lie in the square groove. Such a groove is usually provided either in the casing body, or in the cover that seals it. Usually the three sides of groove square belong to one part, while the second part closes the remaining fourth.
The exception is seen in the Ikelite watertight box crosscut, where the cover and the box form the three sides for the O-ring square seat, while the fourth is open to the water and pressure ambient. And while all the other sealing types provide fixed closure, only O-ring will move to adjust itself under water pressure. The Ikelite type uses water pressure to progressively push the lid down onto the O-ring so as to form even more solid seal. This type of sealing does its work equally well as the other O-ring principles shown, but the better part is in the ease of Ikelite’s O-ring replaceability, removal and maintenance.
Properly greased O-rings
O-rings move and deform under water pressure. They wedge themselves in the corner open to the inner, lesser pressure. To enable it to move, O-ring and its groove must be lightly greased. A proper grease must be used, depending upon O-ring material, so follow the manufacturer’s suggestion!
The grease adds nothing to actual watertighting but many people tend to overgrease, thinking “the more the better.” This is dangerously wrong. Surplus grease collects sand, hair and salt crystals, which may effectively break the sealing and let the water where it doesn’t belong.
Properly greased O-ring is just grease-shiny – not more. To remove it for cleaning and greasing purposes, the easiest way is to slide the O-ring with two fingers along its groove toward one side until it pops out. After cleaning it first, lightly grease a q-tip and run it all along the groove. Nothing but a thin film of grease should remain. Grease the O-ring by pulling it trough greasy fingers. Carefully put the O-ring back into the groove – and that’s all the maintenance it requires!
If you won’t use your camera casing for longer time, remove maintenance-accessible O-rings and save them separately. This way these will retain their form. Prior to the next use, just clean and re-grease as described.
If you take care of your camera or casing and its sealing elements, these will serve you long and well.
More information about underwater cameras and housings