Cave diver with head-mounted light
|Uses||Providing light underwater for safety, navigation, communication, facilitating work or restoring colour|
A dive light is a light source carried by an underwater diver to illuminate the underwater environment. Scuba divers generally carry self-contained lights, but surface supplied divers may carry lights powered by cable supply .
Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done.
Surface-supplied diving is diving using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from scuba diving, where the diver's breathing equipment is completely self-contained and there is no link to the surface. The primary advantages of conventional surface supplied diving are lower risk of drowning and considerably larger breathing gas supply than scuba, allowing longer working periods and safer decompression. Disadvantages are the absolute limitation on diver mobility imposed by the length of the umbilical, encumbrance by the umbilical, and high logistical and equipment costs compared with scuba. The disadvantages restrict use of this mode of diving to applications where the diver operates within a small area, which is common in commercial diving work.
A dive light is routinely used during night dives and cave dives, when there is little or no natural light, but also has a useful function during the day, as water absorbs the longer (red) wavelengths first then the yellow and green with increasing depth. By using artificial light, it is possible to view an object in full color at greater depths.
Water is responsible for the attenuation of light due to absorption so use of a dive light will improve a divers underwater vision.As the depth increases, more light is absorbed by the water. Color absorption depends on the purity of the water - pure water is most transparent to blue frequencies, but impurities may reduce this significantly. Color vision is also affected by turbidity and larger particulate matter.
Underwater, things are less visible because of lower levels of natural illumination caused by rapid attenuation of light with distance passed through the water. They are also blurred by scattering of light between the object and the viewer, also resulting in lower contrast. These effects vary with wavelength of the light, and color and turbidity of the water. The vertebrate eye is usually either optimised for underwater vision or air vision, as is the case in the human eye. The visual acuity of the air-optimised eye is severely adversely affected by the difference in refractive index between air and water when immersed in direct contact. Provision of an airspace between the cornea and the water can compensate, but has the side effect of scale and distance distortion. The diver learns to compensate for these distortions. Artificial illumination is effective to improve illumination at short range.
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.
| A. Metal case containing electrical fittings.|
B. Glass globe and incandescent lamp.
| C. Stand, which also protects the globe.|
D. Ring for suspending lamp.
Early underwater lights were fixed electric flood lamps or portable lamps with dry batteries for use by divers in standard diving dress.Siebe Gorman & Company Ltd developed a model of portable lamp with a parabolic lens and attached to the divers corselet via a ball and socket joint allowing the diver to use both hands while working.
Standard diving dress is a type of diving suit that was formerly used for all underwater work that required more than breath-hold duration, which included marine salvage, civil engineering, pearl shell diving and other commercial diving work, and similar naval diving applications. Standard diving dress has largely been superseded by lighter and more comfortable equipment.
Siebe Gorman & Company Ltd was a British company that developed diving equipment and breathing equipment and worked on commercial diving and marine salvage projects. The company advertised itself as 'Submarine Engineers'. It was founded by Augustus Siebe, a German-born British engineer chiefly known for his contributions to diving equipment.
In 1906, the tungsten filament was introduced and used to produce 200 to 3,000 candlepower dive lights.The Siebe Gorman & Company introduced a 250-watt mercury vapor hand lamp in 1919 that could produce as much as 18,000 candles. For diving in turbid water, 45-watt Sodium hand lamps became the preferred choice. These early lights had to be turned on underwater to avoid cracking the heated glass as it entered cold water.
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. The name tungsten comes from the former Swedish name for the tungstate mineral scheelite, tung sten or "heavy stone". Tungsten is a rare metal found naturally on Earth almost exclusively combined with other elements in chemical compounds rather than alone. It was identified as a new element in 1781 and first isolated as a metal in 1783. Its important ores include wolframite and scheelite.
Candlepower is an obsolete unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents. The historical candlepower is equal to 0.981 candelas. In modern usage, candlepower is sometimes used as a synonym for candela.
The first lantern available to the US Navy had 150 candlepower.The early testing showed a need to increase the length of cable on the US Navy Standard Lantern from 125 feet to 250 feet in 1915 to allow for greater operational range. The United States Navy Experimental Diving Unit continues to evaluate dive lights for wet and dry illumination output, battery duration, watertight integrity, as well as maximum operating depth.
The United States Navy Experimental Diving Unit is the primary source of diving and hyperbaric operational guidance for the US Navy. It is located within the Naval Support Activity Panama City in Panama City Beach, Bay County, Florida.
Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting is sometimes used as the main source of light during daytime in buildings. This can save energy in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants.
There are several options when it comes to light head/bulb types:
Xenon (incandescent) - emit a warm natural light, and tend to be the less expensive, however, offer less brightness and have a shorter battery life than LED or HID lights.
LED (light emitting diode) - are very durable, efficient and powerful.
HID (high intensity discharge) - are extremely powerful and have a nearly white beam. On the downside, HIDs are very delicate and quite expensive.
A modern dive light usually has an output of at least about 100 lumens. Bright dive lights have values from about 2500 lumens. Halogen lamps provide this light at over 50W power consumption. High-intensity discharge lamps (HID)and Light-emitting diodes (LED) can provide similar output for less power.
The light source and the power supply are housed in the same water and pressure resistant housing. The light is switched on and off by a mechanism built into the housing
Canister lights originated when the battery size required for sufficient burn time of a high output light was too large to be conveniently carried in the diver's hand.The work-around was to use a light-head with the light source, which is small and light enough to easily carry in the hand or on a head mount, and provide power through a cable from a waterproof battery canister, which is carried on the diver's harness.
Head mount lights are used by divers who need to use both hands for other purposes. This can be underwater work by a commercial diver, or getting through tight restrictions for a cave or wreck diver. With a head mount there is a greater risk of dazzling other divers in the vicinity, as the lights move with the diver's head, and this arrangement is more appropriate for divers who work or explore alone.[ citation needed ] Helmet mounts are common for commercial work which is often monitored by a helmet mount closed circuit video camera.
Both one piece lights intended to be hand held, and light heads powered from canisters or surface supplied cables are used for head mount lights. There are also a few one piece lights specifically made for head mounting, and a full face mask made by Ocean Reef which has integrated lighting.
Caving head lights are sometimes usable as head mount lights for shallow cave dives, as they are waterproof, but they are generally not designed to be used under much pressure.[ citation needed ]
If the diver is supplied with breathing gas from the surface, it is convenient to supply power for lights from the surface through the same umbilical. An extra cable is generally used for this purpose. The light head is functionally the same as for a canister light, and is usually mounted on the helmet.
Several materials are used for housings. Injection moulded plastics are most popular for the low end and some of the more powerful lights produced in large quantities. Low volume products and home built lights are generally machined from aluminium alloy or high grade engineering plastics such as acetal (Delrin), or occasionally stainless steel, brass or bronze. Lenses (ports) are usually high grade transparent plastic or toughened glass. O-ring seals are standard for sealing joints and connections and for sealing penetrations through the watertight housing for switch controls.[ citation needed ]
Alkaline batteries, zinc-carbon batteries, Nickel–metal hydride batteries (NiMH), lithium-ion batteries, lead-acid batteries,and surface supply by cable are commonly used as power supply.
Voltage depends on the requirements of the specific light source and usually ranges from 1.2V for a single NiMH cell, to 12V for a lead-acid accumulator.Surface powered helmet lights may use 24 or 36V power supplies. High voltage is not generally used except in the final stage of the HID circuit, for safety reasons.
Lights which must be switched on or off underwater require a switch which is unaffected by the pressure and is waterproof.
Technical divers often use a Goodman type handle to carry a light on the back of the hand, so the hand can be used without dropping the light. This handle type was originally rigid, and used to carry a canister light head, but is now also used for small one piece lights. Derivatives use bungee to hold the light in place
Narrow beam (spotlight) vs wide beam (floodlight), vs focusing (by adjustable lens or reflector):
Beam angle is chosen to suit the conditions and activities of the planned dive. Cave divers frequently choose narrow beam lights when diving in good visibility as these provide good illumination over relatively long distances, which is useful when navigating into an unfamiliar space where it is actually possible to see a fairly long distance ahead. Some feel that in poor visibility, or at short range, a narrow beam is not much use, and a wider beam spreads the light over a more useful area. Others feel that in low visibility settings a wide beam angle is distracting as it tends to reflect back to much light from floating particulates (back-scatter). Video lighting usually requires a wider beam as the view angle of the video camera must be accommodated for good results. In the case of very wide angle video, such as the GoPro and similar, an extremely wide angle beam is necessary.
Beam angle may be as tight as 8 to 10 degrees in extreme cases, or as wide as around 140° with a plain flat glass port. Even wider angles are possible (exceeding 180°) with a domed port on the light, or a "test tube" light without reflector. LED lights usually use an internal "lens" to produce a focused beam. This actually focuses the beam by internal reflection on a parabolic surface. Several lens options may be available for different beam angles for a given LED, but most models of light use only the one chosen by the manufacturer.
A few underwater lights have a focusing facility by which the beam angle can be adjusted. There are two ways this can be done, depending on the basic emission pattern of the light source. HID lights, which generally produce non-directional light, are usually focused by a reflector, which can be slid longitudinally over the light. They produce a beam with a central bright area and a diffuse general illumination around it. This is good for illuminating a combination of near and far areas at the same time, but not good for wide angle video, as the hot-spot will confuse the automatic exposure software and the result is generally overexposure in the hot spot and underexposure around it.
Other lights use a lens system over the front of the light, which may be focused by axial movement of the lens, which may be on a screw thread for fine control.
Primary, backup, video light
Usually a powerful light suited to the planned activity of the dive, with sufficient power and suitable beam angle. The beam angle and light output required depend on the objectives of the dive.
Backup lights are carried in case the primary light fails during the dive. This is particularly important in cave and wreck penetration diving, where the light is required to facilitate navigation out of the enclosed space. Cave divers are trained to carry three dive lights as a result of an accident analysis by Sheck Exley published in 1977.
Video lights are a special application. They are generally not important for dive safety, but are required for the video camera to get an acceptable image quality, either for video recording, or for the surface team to monitor the work done by the diver. Modern underwater video lights are now relatively small, have run times of 45–60 minutes and output 600-8000 lumens. These LED lights are powered by Lithium-ion batteries and usually have a 5600K (daylight) color temperature.
A scuba set is any breathing apparatus that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment which is required for providing breathing gas to the diver, general usage includes the harness by which it is carried, and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge, and in the looser sense it has been used to refer to any diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface supplied diving systems, and is allowed by the relevant code of practice.
A flashlight is a portable hand-held electric light. The source of the light is usually an incandescent light bulb (lamp) or light-emitting diode (LED). A typical flashlight consists of the light source mounted in a reflector, a transparent cover to protect the light source and reflector, a battery, and a switch. These are supported and protected by a case.
Underwater photography is the process of taking photographs while under water. It is usually done while scuba diving, but can 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.
Cave diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers lost while diving for one of these reasons. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves decompression.
A diving helmet is a rigid head enclosure with a breathing gas supply used in underwater diving. They are worn mainly by professional divers engaged in surface-supplied diving, though some models can be used with scuba equipment. The upper part of the helmet, known colloquially as the hat or bonnet, may be secured to the diver or diving suit by a lower part, known as a neck dam, breastplate, or corselet, depending on the construction and regional language preferences.
A diving mask is an item of diving equipment that allows underwater divers, including scuba divers, free-divers, and snorkelers, to see clearly underwater. Surface supplied divers usually use a full face mask or diving helmet, but in some systems the half mask may be used. When the human eye is in direct contact with water as opposed to air, its normal environment, light entering the eye is refracted by a different angle and the eye is unable to focus the light on the retina. By providing an air space in front of the eyes, the eye is able to focus nearly normally. The shape of the air space in the mask slightly affects the ability to focus. Corrective lenses can be fitted to the inside surface of the viewport or contact lenses may be worn inside the mask to allow normal vision for people with focusing defects.
Diver communications are the methods used by divers to communicate with each other or with surface members of the dive team. In professional diving, communication is usually between a single working diver and the diving supervisor at the surface control point. This is considered important both for managing the diving work, and as a safety measure for monitoring the condition of the diver. The traditional method of communication was by line signals, but this has been superseded by voice communication, and line signals are now used in emergencies when voice communications have failed. Surface supplied divers often carry a closed circuit video camera on the helmet which allows the surface team to see what the diver is doing and to be involved in inspection tasks. This can also be used to transmit hand signals to the surface if voice communications fails. Underwater slates may be used to write text messages which can be shown to other divers, and there are some dive computers which allow a limited number of pre-programmed text messages to be sent through-water to other divers or surface personnel with compatible equipment.
A full-face diving mask is a type of diving mask that seals the whole of the diver's face from the water and contains a mouthpiece, demand valve or constant flow gas supply that provides the diver with breathing gas. The full face mask has several functions: it lets the diver see clearly underwater, it provides the diver's face with some protection from cold and polluted water and from stings, such as from jellyfish or coral. It increases breathing security and provides a space for equipment that lets the diver communicate with the surface support team.
An umbilical cable or umbilical is a cable and/or hose that supplies required consumables to an apparatus, like a rocket, or to a person, such as a diver or astronaut. It is named by analogy with an umbilical cord. An umbilical can, for example, supply air and power to a pressure suit or hydraulic power, electrical power and fiber optics to subsea equipment and divers.
Sidemount is a scuba diving equipment configuration which has scuba sets mounted alongside the diver, below the shoulders and along the hips, instead of on the back of the diver. It originated as a configuration for advanced cave diving, as it facilitates penetration of tight sections of cave, allows easy access to cylinder valves, provides easy and reliable gas redundancy, and tanks can be easily removed when necessary. These benefits for operating in confined spaces were also recognized by divers who conducted technical wreck diving penetrations.
Diver navigation, termed "underwater navigation" by scuba divers, is a set of techniques—including observing natural features, the use of a compass, and surface observations—that divers use to navigate underwater. Free-divers do not spend enough time underwater for navigation to be important, and surface supplied divers are limited in the distance they can travel by the length of their umbilicals and are usually directed from the surface control point. On those occasions when they need to navigate they can use the same methods used by scuba divers.
A silt out is a situation when underwater visibility is rapidly reduced to functional zero by disturbing fine particulate deposits on the bottom or other solid surfaces. This can happen in scuba and surface supplied diving, or in ROV and submersible operations, and is a more serious hazard for scuba diving in penetration situations where the route to the surface may be obscured.
David John Shaw was an Australian scuba diver, technical diver, and airline pilot for Cathay Pacific, flying the Lockheed L-1011 Tristar, then the 747-400, and then the A330-300, A340-300, and A340-600. He flew for Cathay Pacific from 1989 until his death in 2005. Before flying for Cathay Pacific he flew for Missionary Aviation Fellowship in Papua New Guinea and Tanzania. He also flew agricultural aircraft in South Australia and New South Wales.
Diving equipment is equipment used by underwater divers to make diving activities possible, easier, safer and/or more comfortable. This may be equipment primarily intended for this purpose, or equipment intended for other purposes which is found to be suitable for diving use.
This is a glossary of technical terms, jargon, diver slang and acronyms used in underwater diving. The definitions listed are in the context of underwater diving. There may be other meanings in other contexts.
Scuba skills are the skills required to dive safely using self-contained underwater breathing apparatus, (scuba). Most of these skills are relevant to both open circuit and rebreather scuba, and many are also relevant to surface-supplied diving. Those skills which are critical to the safety of the diver may require more practice than is usually provided during training to achieve reliable long-term proficiency
Doing It Right (DIR) is a holistic approach to scuba diving that encompasses several essential elements, including fundamental diving skills, teamwork, physical fitness, and streamlined and minimalistic equipment configurations. DIR proponents maintain that through these elements, safety is improved by standardizing equipment configuration and dive-team procedures for preventing and dealing with emergencies.
Surface supplied diving skills are the skills and procedures required for the safe operation and use of surface-supplied diving equipment. Besides these skills, which may be categorised as standard operating procedures, emergency procedures and rescue procedures, there are the actual working skills required to do the job, and the procedures for safe operation of the work equipment other than diving equipment that may be needed.