Guides & Tutorials

Photography and Underwater Photography Glossary of Terms

Photography is defined as the process or art of producing images of objects on sensitized surfaces by the chemical action of light or other forms of radiant energy.
Underwater Photography is defined as the process of photography under the water.

Basic Photography Terminology

Angle of View Determined by the focal length of the lens, the angle of view is the area of a particular scene that a lens covers, or, what the lens can “see”. See different lens types below. The angle of view is measure in horizontal and vertical degrees.

Aperture (F-Stop) The opening of the lens through which light passes through. Aperture is measured in f-stops. The smaller the number, the larger the lens opening, and the larger the number, the smaller the opening and the less light allowed to reach the sensor. Aperture also controls depth of field, a smaller aperture (larger number) will produce maximum image sharpness, while a larger aperture (smaller number) will blur the scene around the subject.
Aperture is mostly used in underwater photography with an external light source (strobe or video light) to detemine the amount of ambient light vs the amount of artificial light in the image.

Small Depth of Field Large Depth of Field
Aperture of f/4.5 – the area around the kitten is blurred, only his face is focused. Aperture f/14 – the entire kitten is in focus.

Depth of Field The distance between the nearest and furthest objects that appear acceptably sharp in a given photograph. Or, in other words, the range of sharp focus beyond and in front of the main object the camera is focused on.
It is common in underwater photography that macro images are shot with a small depth of field and wide angle images with a large one.

Large Depth of Field
Small Depth of Field

The top image has a large depth of field. The flowers in the background are just as sharp as those in the foreground.
This bottom image has less depth of field, at f/6.3. Only the flowers directly in front of the camera are sharp and focused.

Exposure The amount of light allowed to reach the sensor, in the case of digital cameras. The amount, or intensity of the light reaching the sensor is manipulated by the lens opening, and the duration of time that the light is able to strike the sensor is controlled by shutter speed.

Over Exposed Image Underwater Under Exposed Image Underwater
An over-exposed underwater image An under-exposed underwater image

Exposure Value (EV) A number representing all available combinations of aperture and shutter speed resulting in the same exposure (with scene brightness remaining the same). The EV +/- setting on the camera is used to make the image more or less exposed in automatic modes (ones that the camera calculates the Aperture and shutter speed).
It is common in ambient light underwater photography to under expose the image by 1/3 or 2/3 stop to give the water a deeper blue color.

Focal Length Measured in millimeters, focal length is the distance between the sensor and the optical center of the lens, when focused on infinity. The focal length is usually marked on the lens itself, sometimes with a range (example: 55mm-250mm). For more on focal length, see the section on lenses.

Macro (Photography) Also called photomacrography, this is the process of taking pictures of very small objects at 1x reproduction ratios or greater.
Macro photography is perhaps the most common type of photography underwater. The existence of so many tiny creates in unique shapes and impressive colors has made this form of photography very popular. Due to the close proximity of the object from the camera, these type of underwater shots are usually the clearest and most impressive as very little water lies between the lens and the object.

Macro Shot Underwater
Macro shot Underwater

White Balance The process of removing undesirable white colorcasts. Digital cameras are not as good as the human eye at judging what is white under different light conditions when using Auto White Balance modes. If pictures are coming out with a blue, yellow, or green cast, the camera is having difficulty adjusting the white balance, which is relative to the “color temperature” of a light source.
This is one of the most important concepts in underwater photography. The water serves as a Blue filter thus eliminating the Red tones in the image more at every depth increase. This results in very blueish photos that lack the original color of the objects shot. This can be corrected in a few ways:

  • Using a Red filter (see filter terms)
  • Shooting RAW (see RAW) and using post processing to set the white balance.
  • Shooting with Manual White Balance mode – The camera usually calculates the white balance automatically. Underwater, it has trouble doing so as it does not have a white reference point to use. Manual white balance is the process of pointing the camera to a white or grey card (sometimes the ait tank can be used) and having the camera calculate the white balance according to that reference point.
Auto White Balance Underwater Manual White Balance Underwater
Shot with Auto White Balance Shot with Manual White Balance

Camera Features & Settings

Aperture Priority – This is a mode where the user sets the aperture and the camera decides the shutter speed. User controls depth of field, while the camera makes a smart, corresponding choice for shutter speed based on the user’s decision. This is a common mode to shoot at underwater without an external strobe and using the EV +/- to determine the exposure of the image. (With a strobe, manual mode is needed to set the amount of ambient light vs strobe light)

Automatic Exposure (AE) Aperture Priority, Shutter Priority, and programmed Auto Exposure are all forms of automatic exposure. When clicking the half shutter button, the AE is locked and the camera can me moved while maintaining the same exposure. There is also a dedicated button in many cameras called AE-L which locks the AE when pressed and allows taking multiple shots with the same calculated AE.

Flash / Strobe Artificial light source that provides the light necessary for taking photos in dark or low light conditions. Provides a brief, intense flash of light that is generally considered to be comparable to daylight. Usually come built into the camera, but additional higher-powered flash accessories are available.
In Underwater photography, a flash is called a strobe. It is basically a waterproof , depth rated flash that connects to the camera by a fiber optic cable or electric sync cord. Due to the lack of light and colors when shooting underwater, a strobe is a must accessory and is being used by the vast majority of photographers underwater.

Flash /Strobe Exposure Compensation Compensates for flash output when flash is used in Auto or TTL mode, adjusting the level of illumination provided by the flash. Exposure is unaffected. This setting is a very important one for UW photography, it can be changed either on the camera itself or on some strobes which support it. The strobe exposure compensation allows the user to have the image lit more or less by the strobe while still keeping the same , correct exposure. This can be used to reduce the amount of ambient light thus darkening the water background. When shooting in Auto/P/Av or Tv this is the only way to control the amount of ambient light vs strobe light. It is generally not needed when shooting manual but some cameras allow Automatic flash exposure (TTL) in Manual mode and in this case the setting will be efficient as well.

Focus Simply put, this is the act of adjusting a lens in order to produce a sharp image. More technically, what happens is that focal length is minutely adjusted to bring a desired subject into sharpness, thus “focused”. There are several types of focus:

  • Manual (MF) The camera user directly manipulates focus, by hand, to bring an object into focus. A dial is usually located at the front of the camera lens, and essentially adjusting this dial even minutely brings the subject in or out of focus by adjusting focal length.
  • Automatic Focus (AF) The camera lens automatically adjusts its configuration to focus on a subject, whether near or far, by using a combination of a sensor, a motor, and a control system. Usually guided by brackets provided in the viewfinder.
  • Focus-Assist (Light) A feature in which the camera sends out a flash of light to lighten up the subject, assisting with autofocus in low light situations. It is very common to carry an external focus light underwater as most cameras do not focus as well underwater as they do above water. Also , the built in focus assist light is usually blocked by the housing or lens port.

ISO – (International Standards Organization) The ISO number represents the film or sensor’s sensitivity to light. A higher ISO means more sensitivity and less light needed for a proper exposure. The lower the ISO, the more light is needed in order for a desirable photo to result.

Live View in digital cameras (more specifically DSLR), live view allows the user to switch to using the electronic display as a viewfinder. This can be used as a tool to frame and preview the photo before taking a shot. Because the camera has to project the preview, this option can sometimes slow the camera down. Live view is starting to be very popular for underwater use as the new DSLR’s perform very well in this mode and looking at a 3″ screen is much easier than a small eyepiece especially with a mask on and other equipment.

Manual Manual Exposure Mode (M) User selects both the shutter speed and the aperture. This mode is used to override the camera’s settings when you believe it is being thrown off (perhaps by low or very high light) or you wish to manipulate the recommended settings for creative effect. Almost every good underwater shot was taken this way. The cameras do not perform well enough undewater to be using any form of automatic calculation therefore , even the beginning photographer is forced to use Manual mode.

Rear Curtain Sync When a flash is fired a second before the rear curtain of the focal plane shutter begins to move. In other words, the flash fires at the end of the exposure. This is used a lot in sport photography, because it can show a ghost trail behind the subject as the subject moves.

Shutter Priority (Tv or S) User chooses shutter speed, camera selects a corresponding aperture. This setting is often used when trying to capture movement; a higher shutter speed will freeze the moving subject. Slower shutter speeds will produce blur.

Shooting Mode The range of options that give you limited or total control over camera settings. Can refer to the various live shooting modes available such as Manual, Auto, Close-Up, Landscape where the camera may choose options for the user automatically, or the user sets them all themselves. Less commonly refers to the actual photo shooting Continuous, timed, or single – in other words, how often/quickly the camera snaps a picture when pressing the shutter once.

Shutter The mechanical device on a camera that opens and closes to control the time of photographic exposure, or how long the sensor or film is exposed to light. Can also refer to the button you press to initiate the camera to take a photograph.

Shutter Speed Determines how long the sensor will be exposed to light, by changing how quickly the shutter opens and closes. It affects the degree to which subjects will appear frozen or blurred. Due to the fact that water is much thicker and dense than air, it serves as a vibration absorbant and therefore photographer body shakes are much less disturbing. It is more common to use slower shutter speeds underwater and get good results.

Shutter Speed Blur Shutter Speed - Fast
This Shutter Speed was set far too low, making a subtle movement cause image blur.. This shutter speed, aperture, and exposure are perfect, capturing a moving horse without blurring any part of the image. To blur the background, a larger aperture could have been used.

VR (Vibration Reduction) Nikon image stabilization technology that minimizes blur by reducing camera shake.

NR (Noise Reduction) Camera noise is present when colored speckles appear where there should be none. Noise Reduction technology ‘tightens” these particles. Most digital SLR’s are very sufficient at reducing noise, especially at the proper settings.

TTL (Through The Lens) Commonly used to refer to metering that is done through the lens, and not with a separate device. This method is mainly used for focusing and for automatic flash exposure. In underwater photography , the term TTL automatically correlates the Automatic exposure calculation with a strobe. A strobe that supports TTL can be put on auto mode and will fire at the amount necessary to correctly expose the image. This information is synced from the camera by fiber optic means ( imitating the built in flash) or by sync cord (electronic fire and cease pulses).
As the image changes rapidly underwater due to moving fish and currents, shooting manual with a strobe is challenging , more than using a flash above water, for this reson , TTL is very helpful and is used by many.

Accessories

Filters Filters are attachments that go over the front of the lens. They produce photo effects and help reduce certain issues by ‘filtering’ what the lens sees. With digital photo enhancement the way it is today, many people don’t believe they need filters. However, there are just some things you cannot change, even with a photo editor.

  • UV Absorb ultraviolet rays and atmospheric haze. These filters can be left on all the time to protect the lens as they have no effect on images aside form absorbing rays and reducing haze.
  • Skylight Reduce color inconsistencies when photographing outdoors, especially in shade. Can also reduce shadows from appearing on skin tones.
  • Polarizing Remove reflections from non-metallic surfaces (water, glass) and enhance vibrancy and clarity of colors.
  • B&W/Sepia/Color Correcting These filters can be considered useless because most cameras come with included settings that allow you to change color. However, with the filters the photographer is able to preview the image with the color changes already in effect instead of waiting to see what they look like once taken. A Red filter for seawater and Pink filter for fresh water a very common to use underwater in order to correct the loss of color.
  • Intensifying These filters intensify a particular color. They can be used to make grass or sky appear more vibrant, but will cast the color onto other colors as well.
  • Macro Macro filters help a regular lens to better take extreme close up shots, without buying a macro lens itself. A Macro filter , also called a diopter or close-up filter is very common to use underwater to allow taking shots of small creatures without getting very close to them and forcing them to run away. Such macro filters can also be mounted outside the housing , this is called a wet filter or wet lens.

Flash Diffuser – A flash diffuser is a white semi-transparant plastic mounted over the flash in order to disparese the light for softer look and wider angle coverage.

Lens By definition a lens is one or more pieces of optical glass or similar material designed to collect and focus rays of light to form a sharp image on film, paper, or a projection screen. Think of the lens as the “eye” of the camera. A normal lens has a perspective (or viewing angle) much the same as a normal human eye. Lenses are identified by their focal length (see Focal Length), in millimeters. Camera lenses are made in a whole range of viewing angles.

  • Telephoto Also referred to as “Long Lenses”, telephoto lenses compress space, while magnifying far off objects. They have a longer focal length, and the longer the focal length, the more they compress and magnify the scene. They have shallow depth of field, and are sometimes referred to as portrait lenses because they make the subject stand out.
    Telephoto lenses are less used underwater due to the fact that distance is a serious obstacle for good shots. The more water between you and the subject the image will not be as clear. Common ranges for shooting underwater is 2 Inches to 5 feet.
  • Wide-Angle Just like it sounds, a wide-angle lens has a smaller focal length and makes the scene appear deeper and wider. They have deep depth of field and high close-focusing abilities.We’ve mentioned in Telephoto that distance is an obstacle , wide angle leses allow you to take the same shot at a closer distance. This makes them very popular for underwater use.
  • Zoom These lenses generally have a range of focal lengths, in millimeters. They are a combination of wide-angle and telephoto lenses. For example, a 10x zoom has a range from moderate wide-angle to long telephoto. These lenses allow the user to manipulate the focal length without changing the focus.

Zoom Lens
Photo taken with a zoom lens at 250mm, ISO 100, f/5.6.

  • Macro Macro lenses are designed to magnify a subject far more than a regular lens can accomplish, being able to capture very fine detail in subjects too small for the naked eye to see. These lenses are used to take extreme close up photographs, generally of very small objects. As previously mentioned Macro is very popular underwater and so are Macro lenses.
  • Fish Eye A lens with an extremely wide angle of view, up to 180 degrees, usually with a short focal length. It produces an image with a distorted angle of view, usually circular. Depth of field is practically infinite with most of these lenses. The water has a natural magnification effect, therefore the fisheye effect is reduced underwater and these lenses serve as very wide wide angle lenses and are extremely popular.

Fisheye Lens
Photo taken with a fisheye lens.

Lens Hood an attachment for the front of the lens that prevents undesirable light from striking the lens and causing flare. Come in different sizes, and should always be sized per lens to avoid an unwanted vignette effect (underexposure in the corners of the photo).

Tripod A Tripod is a three-legged camera stand that allows the user to reduce vibration/shake when taking images that require a still hand (slow shutter speeds, when using an extreme telephoto lens, etc.). A monopod serves the same purpose, but stands on only one leg, therefore helps to steady the camera, but not to the extent of a tripod.

Tripod Shots
This night photo of Cleveland, Ohio would have benefited from the use of a tripod to clarify and sharpen the lights of the city.

Bits & Pieces

JPEG The most widely used file format, but it compresses the file sizes up to 90%, causing reduction of image quality. To compress the files, some date must be thrown away, and the amount of loss of data is relevant to loss of photo quality, and depends on how much the file is compressed. Most cameras offer various options for file format and size. At the highest JPEG setting, quality will not change much to the naked eye, but for purposes of editing and/or resizing, the less compression, the better.

RAW (File) “Digital Negative” The only file format that does not include any compression, it records the images exactly how the were seen by the camera, making no adjustments. RAW files are pure digital images that have had little to no processing applied by the camera. So when the images are loaded unto a computer, the user can make any corrections there. The camera has not applied color or exposure correction, sharpening, or white balance, so these can all be adjusted by the user upon upload to a computer! Example: If you took a photo in RAW format and your ISO was off, you can literally go back in and reset the ISO speed from the computer. It’s like being able to go back in time and fix mistakes.

Megapixel (MP) A “pixel” is short for “picture elements” and they are little squares that make up the building blocks of an image. If you were to blow up a photograph to its maximum magnification, you would be able to see these pixels. It takes millions of them to make a high quality image. The more megapixels a camera has, the sharper and more detailed the images, even when blown up into larger images. Pixels can also differ in size among cameras; digital SLR’s generally have larger pixels, therefore creating better images in lower light levels.

Brand Specific Terminology

AF-I (Nikon) Lens with built-in CPU and autofocus drive motor.
AI (Nikon) Stands for Automatic Index, which is Nikon’s system for relaying to the camera’s exposure meter what the maximum aperture is for a particular lens.

AI/s (Nikon) Stands for Automatic Index/Shutter, which is Nikon’s lens mount that permits automatic operation in shutter-priority mode and programmed auto-exposure systems.

USM (Canon) Stands for Ultra Sonic Motor, Canon’s quietest and fastest autofocus lens system.

EOS (Canon) Electronic Optical System, an entire line of autofocus cameras by Canon.

E-TTL (Canon) Evaluative through the lens flash monitoring.

Camera Types & Parts

Mirror-less Camera These digital cameras are without mirrors, so are also without a viewfinder. Only way to preview pictures is to use the LCD screen. They are lighter and more compact than regular DSLR’s, until you add lenses. Mirror-less cameras are becoming very very popular underwater. As the housing and accessories make the system very big , having a compact camera at DSLR quality can be a huge advantage. Another reason is that viewfinders are much less comfortable to use underwater and the standard of shooting with an LCD monitor is much more appropriate.

Micro 4/3rd’s Cameras A standard created by Panasonic and Olympus for digital mirror-less interchangeable lens cameras. They are kind of an in-between camera, fitting somewhere between compact digital camera’s and digital SLR’s. They are compact, have medium sized sensors, and offer passable image quality.

DSLR Digital Single Lens Reflux Camera. These cameras use a digital mirror system to direct light from the lens to an optical viewfinder on the back of the camera.

Hotshoe A mount, usually on the top of the camera, that allows additional flash to be attached and triggered by the camera, rather than as a separate unit.

LCD Liquid Crystal Display. Used to preview images, take video, and make setting selections.

Sensor (CCD/CMOS) converts an optical image to an electric signal. In other words, it is the digital form of film.

Viewfinder The “window” in which the user looks into to frame, focus, and set the picture. Using the view finder instead of the LCD preview screen allows for more image stability, since the camera must be pressed against the face.

Image Composition and Quality

Flare A composition flaw, caused by stray light passing through the lens that does not become focused with the rest of the photograph. Appears like a “bubble” somewhere on the image, usually of multiple colors. A lens flare can occassionaly happen underwater when positioning the strobes in front of the lens. This can be eliminating by either moving back the strobes or using a lens hood.

Lens Flare
Image flare(towards the right) caused by the sun (upper left). (Photo taken with fisheye lens, hence the distortion)

Golden Rectangle A ratio, used to make the most balanced and pleasing composition for the viewer, (width VS height) allowing the viewer to recognize the central focus of an image as easily as possible.

Latitude The variance between proper exposure and any exposure that still creates a desirable image.

Monochrome Defined as a picture or photograph developed or executed in only black and white, or varying tones of one color. The term monochrome is the more technical term for the more easily recognized, “black and white”.

Resolution Resolution is a loaded term that is most easily described as the sharpness and quality image detail. Resolution quality is directly related to pixels per inch, and the quality of the pixels themselves, which can vary greatly between cameras. Resolution is dependent upon the lens itself and the resolving power of the camera sensor. The two are not related, but image quality is dependent on each of them.

Rule of Thirds A simple composition technique that is used to assure balance in a photograph. The scene is mentally divided into thirds both horizontally and vertically. The placement of key subject matter at the intersections of the thirds creates a balanced division of space within the frame.

Sunny-16 Rule A guideline stating that you can expose a bright and sunny scene at an aperture of f/16 with a shutter speed corresponding to the ISO and produce a proper image. The name is deceiving, as it’s a guideline, not a rule there will be times you’ll have to vary from it.

Value Also known as “tone”, is the degree of lightness or darkness in a photograph, or particular area of a photograph. Value/Tone sometimes gives a photograph a creative effect, whether intentional or accidental. Value/Tone can be easily manipulated to create very interesting changes in the “feel” of a photograph. Cold tones (blues) and warm tones (red) bring out the color of a photograph, even in black and white.

Vignette The underexposure of image corners, usually caused by faulty or poor fitting equipment (such as lens hoods, or poorly designed lenses). Vignette can also sometimes be a setting available in photo editing programs to produce a creative effect. Vignetting can occur underwater when the wrong lens port is used for a lens. It is always important to consult with the manuafacturer before using another lens hood or lens port.
Vignetting
Vignetting caused by a poor fitting lens hood.

Underwater Photography Only Terms

Wet Lens – A wet lens is a lens that can be mounted on top of the housing while underwater. Common ones are wide angle and macro lenses which enhance the optics of compact cameras and improve the macro distance of DSLR’s.

Cold Shoe – Very different than hotshoe , this part is a mount on top of the housing that resembles the hotshoe but does not have any electrical connections. It is simply there to hold a focus light , strobe or action cam.

Fiber Optic Cable – Used to connect the strobe to the housing in order to pass the light on from the cameras built in flash to the strobe’s light sensor. This type of connection is very popular as water does not have any effect on such connection and they are therefore very reliable.

Housing – A camera housing is used to waterproof and depth rate a camera for shooting underwater. Such housing are made of Polycarboncate or Aluminum and is usualy camera model specific.

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