Underwater photography
Underwater photography is the practice of capturing images beneath the surface of the water, often done while scuba diving, but can also be done while diving on surface supply, snorkeling, swimming, from a submersible or remotely operated underwater vehicle, or from automated cameras lowered from the surface.
Underwater photography can also be categorized as an art form and a method for recording data.
Successful underwater imaging is usually done with specialized equipment and techniques. However, it offers exciting and rare photographic opportunities. Animals such as fish and marine mammals are common subjects, but photographers also pursue shipwrecks, submerged cave systems, underwater "landscapes", invertebrates, seaweeds, geological features, and portraits of fellow divers.
Equipment
Some cameras are made for use underwater, including modern waterproof digital cameras. The first amphibious camera was the Calypso, reintroduced as the Nikonos in 1963. The Nikonos range was designed specifically for use underwater. Nikon ended the Nikonos series in 2001 and its use has declined, as has that of other 35mm film systems. Sea and Sea USA made the Motor Marine III, an amphibious range-finder camera for 35mm film.Underwater housings
Cameras made for dry work can also work underwater, protected by add-on housings, which are made for point and shoot cameras, compact cameras with full exposure controls, and single lens reflex cameras. Most such housings are specific to the camera model. Materials range from relatively inexpensive injection molded plastic to higher-priced die-cast or machined from solid aluminum. Housings allow many options: users can choose housings specific to their everyday "land" cameras and use any lens, provided that it fits or they use the appropriate lens port accessory. Underwater photographers generally use wide-angle lenses or macro lenses, both of which allow close focus and therefore a shorter distance to the subject, which reduces the loss of clarity to scattering.Digital media can hold many more shots than standard film. This gives digital cameras an advantage, since it is impractical to change film underwater. Other comparisons between digital and film photography also apply, and the use of film under water has declined, as it has on land. It is also not possible to change regular lenses underwater, though some wet connectable telephoto, fisheye and macro extensions are available for some housings.
Underwater housings have control knobs and buttons that reach the camera inside, allowing use of most of its normal functions. These housings may also have connectors to attach external flash units. Some basic housings allow the use of the flash on the camera, but the on-board flash may not be powerful enough or properly placed for underwater use. More-advanced housings either redirect the on-board strobe to fire a slave strobe via a fiber-optic cable, or physically prevent the use of the on-board strobe. Housings are made waterproof by silicone or other elastomer O-rings at the closures and where control spindles and pushbuttons pass through the housing. High-end housings may use double O-rings on many of the critical pushbuttons and spindles to reduce the risk of leaks, which can destroy the electronics in cameras. Some cameras are inherently waterproof, or submersible to shallow depths; when these are in submersible housings, the consequences of a small leak are generally not serious.
There are optical problems with using cameras inside a watertight housing. Because of refraction, the image coming through the glass port will be distorted, especially with wide-angle lenses. A dome-shaped or fish-eye port corrects this distortion. Most manufacturers make these dome ports for their housings, often designing them to be used with specific lenses to maximize their effectiveness.
The Nikonos series allowed the use of water-contact optics—lenses designed to be used submerged, without the ability to focus correctly when used in air. There is also a problem with some digital cameras, which do not have sufficiently wide lenses built in; to solve this, there are housings made with supplementary optics in addition to the dome port, making the apparent angle of view wider. Some housings work with wet-coupled lenses, which are screwed on to the outside of the lens port and increase the field of view; these lenses may be added or removed under water, allowing both macro and wide-angle photography on the same dive.
With macro lenses, the distortion caused by refraction is not a problem, so normally a simple flat glass port is used. Refraction through a flat port increases the magnification of a macro lens; this is considered a benefit to photographers who are trying to capture very small subjects. Digital cameras may have several user selectable or programmable modes, which may include modes specifically for underwater use.Buoyancy of the housing may have to be adjusted by adding ballast or buoyancy chambers. Ideally these should be incompressible at working depth range so the buoyancy remains constant throughout the dive, and can be set with considerable precision. Most divers can manage a small divergence from neutral buoyancy, but a large divergence can make it difficult to hold the camera in place with one hand, which can often be useful, particularly with point and shoot cameras. When photographing on breath-hold, it is convenient if the camera will float back to the surface if dropped. On scuba it may be more convenient if it does not float away.
Smartphone housings
Underwater housings for smartphones are available with a variety of depth ratings and features. These can be less expensive than dedicated underwater photography cameras. The simplest form is a waterproof pouch, best used for shallow-water photography.Some smartphone housings are limited by operating system. Others are compatible with almost any phone that will physically fit into the housing, but require Bluetooth and an app enabling the phone to communicate with the housing. Wireless communication allows the housing to be made with only one opening hull penetration and no moving parts penetrating the camera compartment. Some housings are pumped down to a near vacuum after sealing, which secures the cover and allows the seal to be tested before entering the water. Some use physical capacitive buttons that interact with the touch screen.
Camera formats
Most types of digital camera have some underwater application. Those commonly seen in use are the models for which stock underwater housings are available, or which are inherently waterproof, such as rugged compact cameras, which may be used at shallow depths without a housing, but have housings available for greater depths.- Compacts, rugged compacts and bridge cameras have great versatility regarding focal length, they tend to have a wide angle to telephoto lens with macro capabilities making these functions available without need to change lenses, which cannot be done during a dive. Although wet change accessories are available to increase or decrease focal length and for greater magnification, the 2020 generation rugged compacts already have inherent very close focus ability, and fairly wide angle low end of the focal length. Some of the rugged compact cameras will fit into a large dry suit or BC pocket in their underwater housing, though not usually with an external strobe or video light, allowing a diver to conveniently carry the camera on a working dive in case it may be useful, or for a larger format photographer to carry it as a backup, or for opportunities where the main camera has an unsuitable lens fitted.
- Action cameras are popular with divers who want a record of the dive, but not the task loading of operating the camera controls. The camera can be hand held for versatility, or can be head mounted for first person view, or mounted on other equipment, like a diver propulsion vehicle.
- Mirrorless interchangeable-lens cameras and Digital single-lens reflex cameras have very similar ranges of applications, mostly for high end work, where the photographer wants the best possible image quality, and has the skills and desire to put in the necessary effort and accepts the limitations of being stuck with the same lens throughout the dive, and managing bulky equipment. These formats are almost always used with large external lighting systems which are needed in most circumstances to get the best results. A relatively large capital investment in equipment is associated with the format.
Lighting
The primary obstacle faced by underwater photographers is the loss of color and contrast when submerged to any significant depth. One issue faced is light attenuation. The longer wavelengths of sunlight are absorbed quickly by the surrounding water, so even to the naked eye everything appears blue-green. The loss of color increases not only vertically through the water column, but also horizontally, so subjects farther away from the camera also appear colorless and indistinct. This effect occurs in apparently clear water, such as that found around tropical coral reefs.
Underwater photographers solve this problem by combining two techniques. The first is to get the camera as close to the photographic subject as possible, minimizing the horizontal loss of color. Many serious underwater photographers consider any more than about one yard or meter unacceptable. The second technique is the use of a flash or video lights to restore colour lost to depth. Fill flash, used effectively, "paints" in missing colors by providing full-spectrum visible light to the overall exposure.
Another environmental effect is range of visibility. The water is seldom optimally clear, and the dissolved and suspended matter can reduce visibility by both absorption and scattering of light.