A flash unit separate from the camera that has either a wireless connection or attaches directly to the camera's hot shoe. Also called external flash, it provides supplemental light to a scene.

The preeminent image-editing software used for adjusting photos. Photoshop comes in two versions: Photoshop Elements for amateur photographers and Photoshop CS for advanced and professional photographers.

The light, natural or artificial, that is found illuminating a subject or scene; the photographer adds no additional light to it. Also called existing light and available light.

An adjustable, circular opening in a lens through which light passes to reach the camera's sensor. It works with shutter speed to deliver the proper amount of light for a correct exposure of a picture. The diameter of the aperture is expressed as an f-stop number; the smaller the f-stop, the larger the aperture.

An exposure mode that allows the photographer to choose the aperture {f-stop); the camera then sets the shutter speed to provide a correct exposure. Also called Av,

An exposure mode in the camera which sets both the shutter speed and the aperture. Depending on the camera model, it may also adjust the ISO and turn on the flash to achieve correct exposure.

A camera function that enables the lens to focus automatically on a specified area in the scene.

At this setting, the light metering gives equal emphasis to all light values reaching the sensor, and then averages them to determine the camera's exposure settings.

The subject is lit from behind—and the light shines directly at you.

A series of exposures that varies the amount of light reaching the sensor. You create a sequence of pictures with different degrees of brightness with the expectation that one of the series will be correctly exposed. Bracket exposures when you think the scene lighting or subjects may fool the camera meter.

A camera function that automatically takes 3 to 7 pictures at different exposures when you press the shutter button.

In a digital image, the lightness value of a pixel is expressed from black to white, with 0 zero) for black and 255 for white.

The computer memory in your camera that temporarily stores digital photos as you take them. Later, the pictures are written to a memory card.

A shutter speed setting that keeps the shutter open as long as the shutter button is depressed. Normally used for time exposures of several minutes and longer.

See Continuous Shooting mode.

An electronic or mechanical cable that attaches to the camera which you use to release the shutter without incurring the vibration or jarring that often occurs when you press the shutter release with your finger.

A metering mode that gives extra emphasis to the center of the picture area when measuring light in a scene.

A special polarizing filter for autofocusing cameras. See polarizing filter.

Also known as a macro lens. It enables the camera to focus extra close to the subject by using a focusing mechanism that extends the lens further out than a conventional lens does; not to be confused with supplementary close-up lenses that screw on to the front of a lens like a filter.

The overall color appearance of a picture. Normally, white subjects should look white and colors should appear natural and match the color in the scene. The color of light varies depending on the source and on the time of day for sunlight. White balance settings on the camera can be used to create neutral results.

A color shift or tint that uniformly covers an image. It is often caused by a mismatch between light source and white balance setting. Can also be caused by light reflected from colored walls and other surfaces.

A specific type of removable memory card used to store pictures in many dSLR cameras.

The arrangement of subjects in a photograph to create a pleasing and meaningful design. Composition is largely a matter of personal taste.

A reduction in the file size of a stored digital picture. This reduction is achieved by algorithms for file compression that evaluate picture data and eliminate redundant information. See also JPEG.

A function that enables the lens to continuously adjust focus as the subject moves, so long as you continue to partially depress the shutter button.

A setting that enables the camera to keep taking multiple pictures once you press and hold down the shutter button. Continuous Shooting mode is also known as Burst mode.

See dynamic range.

See exposure.

To eliminate unwanted portions of a picture with image-editing software.

A camera setting that delays the opening of the shutter by a few seconds, usually to reduce vibration that may occur when the mirror in a dSLR lifts up to admit image-forming light from the lens.

The near-to-far distance in a scene that appears sharp in a picture. Once the camera is ready to take a picture, depth of field is controlled by the aperture setting. Before the camera is set to take a picture, depth of field can be altered by the aperture, camera-to-subject distance, and the lens focal length.

A series of markings on a lens barrel, typically in both feet and meters, which indicates the depth of field for a given aperture setting and subject distance.

Digital single-lens-reflex camera. A digital camera design that uses a pentaprism to bounce the light image from the lens to a view finder via a 45-degree minor.

Backlighting, side lighting, and front lighting are examples of light which strikes a subject from a particular (and usually obvious) direction.

See LCD.

From the lightest to the darkest, the range of tones in a digital photo. The greater the dynamic range, the more detail appears in both shadow and highlight areas. Also called contrast or tonal range.

A device that creates a brief and bright burst of light to enable picture taking when the light is too dim. The light is created by using electricity from a battery to spark a gas (usually xenon) contained in a small tube.

Random electrical signals from the camera's sensor that appear as stray and unwanted colored specks in a digital photo. Noise increases at higher ISOs, because cameras amplify the signal from the sensor, which in turns amplifies or increases the amount of noise. Also called noise and random noise.

A cable that attaches to the camera and allows the photographer to open the shutter without jarring the camera by pressing a button on the cable that sends an electronic signal to the camera and opens the shutter.

Different combinations of aperture and shutter speed settings that let in the same amount of light. For example, 1/125 second at f/16, 1/250 second at f/11, and 1/500 second at f/8 arc equivalent exposures because they admit identical quantities of light when the scene illumination remains unchanged.

Acronym for Exchangeable Image File format. This standard describes how digital cameras can store a variety of picture-taking data in the picture file that can later be reviewed by looking at the Properties portion of the file using a Windows or Macintosh computer. Typical data stored includes a wide variety of camera settings such as shutter speed, f/stop, focus mode, focal length, scene illumination, white balance, file size, and so on.

See ambient light.

The amount of light that reaches the sensor; a correct exposure requires a specific measure of light to give a picture brightness and darkness values that closely resemble the scene. The amount of light reaching the sensor is controlled by shutter speed and aperture setting.

See bracketed exposure.

The process of deviating from the meter recommendation to increase or decrease the amount of light reaching the sensor for artistic or technical exposure reasons; often done to accommodate for shortcomings of the metering system or to customize the setting to a specific subject in the scene.

A setting that automatically increases or decreases exposure.

The camera meter that measures the amount of light when framing a photo and determines the best exposure. Averaging, center-weighted, matrix, and spot are the main metering types.

A series of camera functions that automatically sets the shutter speed and aperture to give good exposure based on predetermined requirement for each mode.

See accessory flash.

The structure of the photo file when it is saved on a camera memory card or a computer hard drive. Common file formats include JPEG, TIFF and RAW.

The use of flash outdoors, usually in sunlight, to lighten deep shadows on faces; can also be used with other subjects. Also called fill-in flash.

Optical quality glass or plastic placed in front of the lens to modify the qualities of light.

A lens with only one focal length as opposed to a zoom lens which has a specific range of continuously variable focal lengths. Also called a prime lens or single-focal-length lens.

Typically the fastest shutter speed in which the shutter fully opens so that the flash can be used. Slower shutter speeds can also be used, but at higher shutter speeds, the shutter forms a slit that travels above the sensor and would cut off part of the light from the flash.

An optical measurement of the internal focusing distance of a lens expressed in millimetres. Commonly used to classify a lens as to whether it's a wide-angle, normal, or telephoto lens.

A measure of the rate at which pictures are taken.

The direction of light that strikes the surface of the subject facing the camera.

A numerical indicator of the size of the lens aperture. Also called f-number.

A lens filter with its density decreasing from the greatest density at the top to no density from the middle to the bottom. Referred to as neutral because it doesn't alter color.

A technique in which a series of pictures of an identical scene are taken in a range from underexposure to normal exposure to overexposure and then combined in special software to extend the dynamic range beyond what a single exposure could reveal.

A graphic display of tonal values in an image. It is a feature on cameras and image-editing software commonly used to evaluate the quality of an image's exposure.

A bracket on the camera used to hold an accessory flash unit.

Computer software designed to enable uses to adjust and manipulate digital pictures. With image editing software, you can darken or lighten a photo, rotate it, adjust its contrast, crop out extraneous detail, remove red-eye and more.

The number of pixels in a digital photo. Often used as an indicator of how much a photo can be enlarged.

Technology that counteracts slight movement of the camera when it is handheld to create sharp pictures taken at slower shutter speeds. Also known as optical stabilization.

A lens technology that employs a movable glass element to counteract slight movement of the camera when it is handheld so as to enable sharp pictures at slower shutter speeds.

The distance setting on the lens at which light rays enter the lens effectively parallel to each other and everything beyond it appears in focus.

Determines the sensitivity of the camera sensor and affects how much light is required to make a correct exposure. Based on the rules from the International Organization for Standardization. This sensitivity is expressed with ISO numbers: ISO 100 is a slow speed and indicates low light sensitivity; ISO 800 is a fast speed and indicates high sensitivity.

The most popular file format used in digital photography. JPEG is the standard method for compressing image data and was developed by the Joint Photographic Experts Group. Compression is used to make image files small enough to store greater quantities of them on memory cards. JPEGs image files are considered lossy in that they get rid of some of the image data when they are compressed.

The time between when you press the shutter release button and the camera takes the picture.

The device on the back of a camera used to display digital pictures and menus.

Designated by the maximum aperture of a lens. A lens with a relatively large maximum aperture is considered fast. One with a medium or small maximum aperture is considered slow.

An instrument that measures light so the camera can deliver the amount of light required by the sensor for a correct exposure of a specific scene. It's built into all modem cameras, but is also available as a separate unit.

See close-up lens.

A camera setting that requires the user to set both the shutter speed and aperture to achieve a correct exposure.

A focus adjustment made by hand-turning the focus ring on the lens.

A setting that requires the user to turn a ring on the lens to adjust the focus.

A meter setting that determines the exposure settings required by variably weighting data through the use of a segmented pattern superimposed on a scene as seen through the viewfinder or LCD.

I See also pixel. One million pixels. The measure often used to indicate a camera's resolution, although it should not be used as an indication of picture quality which also depends on a variety of other factors.

A small and portable electronic storage device for recording and storing pictures from a digital camera.

Data about data. At the time of picture taking, cameras capture a variety of information about camera settings and picture specifications that can be accessed through the camera, your computer's operating system, or your image-editing program.

Individual settings that determine the pattern the meter uses to measure light from a scene; modes include center-weighted, averaging, matrix, and spot metering.

A camera setting that lifts the mirror and locks it in position during picture taking so its movement does not vibrate the camera.

A lightweight, one leg piece of tube about three feet long with a mount to support a camera to enable the use of slower shutter speeds.

A lens filter made of material that reduces the amount of light passing through it without altering the light's color quality. Also called ND filter.

The introduction of unwanted colored pixels into an image. Noise is increased by electronically boosting the signal by setting a higher ISO. Also called electronic noise and random noise.

A lens focal length believed to show a scene similar to how the human eye sees it. In 35mm equivalent focal lengths, this would be about a 50mm focal length lens.

Increasing the size of the aperture to let in more light.

See image stabilization.

A picture that is too bright because too much light was allowed to reach the sensor. It lacks details in the highlights.

The technique of moving the camera to track the subject while using a medium to slow shutter speed. The purpose is to convey a sense of motion by showing the subject fairly sharp against a blurred background.

Another name for picture element, the smallest light-sensitive component of a sensor used to form pictures. A digital photograph's resolution, or visual quality, is measured by the width and beight of the image measured in pixels.

A rotating lens filter (also called a polarizer) that is capable of reducing reflections from nonmetallic surfaces (glass, water, etc.) by filtering out certain angles of light waves. Polarizing filters are also able to darken blue skies (by removing reflections from airborne moisture) and saturate colors. Auto-focus lenses require what is known as a circular polarizing filter.

A camera program that measures the path of a subject as it moves and adjusts focus of the lens after the shutter button is pressed to anticipate the location of the subject when the shutter opens.

To focus on the area of the scene you want to photograph before composing and taking the picture. Often used in action photography.

A lens with one fixed focal length.

The exposure mode that tries to give equal emphasis to shutter speed and f-stop during picture taking.

An industry term used to describe cameras designed to fit the needs of consumers who demand some of the performance features of a professional camera but at a lower cost.

A file format that saves a camera image as an unfinished file that preserves much of the original photo data in an unaltered form. This allows you to make many more broad adjustments in image-editing software than you could with a JPEG or TIFF file.

Rear curtain synch is an electronic flash mode in which the flash fires at the end of the exposure, immediately before the camera's shutter closes.

An electronic device that allows you to press a button to send a signal to the camera to take a picture.

See image resolution.

Intentionally limiting focus to a specific area of the subject for creative effect by restricting a photograph's depth of field.

The camera device that when set and then activated by pressing the shutter button takes a picture at predetermined delay time typically from 2 to 20 seconds.

See ISO speed.

The electronic, light-sensitive device in a camera that records a picture in a digital camera.

An image-stabilization technology that moves the sensor to counteract movement of a handheld camera and thus enable sharp pictures at slower shutter speeds.

The clarity of detail in a photo.

A mechanical device in the camera that opens to admit image-forming light from the lens onto the sensor to form a picture.

An exposure mode that requires the user to set the shutter speed; the camera then selects the aperture to give a correct exposure. Also called Tv.

A button usually on top of the camera that you press to take a picture.

The length of time that the camera's shutter remains open to create an exposure; typically measured in full seconds, hundredths of a second, and thousandths of a second.

Light that shines on a subject from either side and creates shadows that show a subject's dimensionality.

A lens with a fixed focal length that cannot be adjusted; as opposed to a zoom lens which offers a fixed range of focal lengths that the user can select from.

a function that causes the lens to focus once when you partially depress the shutter button. See Continuous Servo focus mode.

A function that results in the camera taking only one picture each time you fully depress the shutter button.

Gentle light that is created from a large, diffuse light source, such as found on a cloudy day or next to a window away from direct sunlight. Also called diffuse light.

A small, often inexpensive camera designed with automatic and often non-adjustable settings to simplify picture taking for casual photographers.

A light meter function that measures only a tiny area of a scene—typically anywhere from a 1- to 5-degree angle of view.

Reducing the size of a lens aperture to decrease the amount of light admitted by the lens.

See memory card and compact flash card.

A rule for manually setting (or checking) exposure for taking pictures of subjects in bright sunlight. "The rule states that the correct exposure for a subject in bright sunlight is to use an aperture of f/16 at a shutter speed of 1/ISO setting on the camera. Example; If the camera ISO is set to 200, the correct exposure would be 1/200 second at f/16 (or an equivalent exposure, such 1/800 second at f/8.

A lens using an optical design that magnifies the apparent size of distant subjects by narrowing the field of view. In 35mm equivalent measurements, a telephoto lens would include focal lengths upwards of 70mm.

A lens with an optical design that both magnifies distant subjects and allows the focal length to be varied through a specified range. Common zoom lenses include 70 – 200mm and 70 −300mm focal length ranges.

Tagged image file format. A standard photo file format. No longer common in cameras but still widely used for saving images in image-editing software because it maintains lossless quality and supports most advanced features, such as layers, embedded by the image-editing program.

See dynamic range.

To took through the camera viewfinder and follow a moving subject with the intent to take its picture.

A camera setting that automatically takes a picture when a subject moves into a preset focus distance within the camera's field of view.

A three-legged camera support used to steady the camera during long exposures.

Acronym. Through-the-lens light metering means that the light is measured at the sensor plane of the camera.

A picture that is too dark because too-little light reached the sensor. An underexposed photograph lacks details in the darker tones.

An optical device built into the camera through which the photographer looks to determine the area to choose to make a picture.

A method of neutralizing color shifts in the existing light source by matching the color response of the digital sensor to the color temperature of the light.

A lens using an optical design that reduces the apparent size of distant subjects by increasing the field of view. In 35mm equivalent measurements, a wide-angle lens would include focal lengths downwards of 40mm.

A lens with an optical design that allows the photographer to continuously change the field of view through a specified focal length range to include more or less of a scene. Such lenses come in a wide variety of focal length ranges, some offering extended focal length ranges from wide-angle to telephoto, such as an 18-200mm lens. Typical ranges include l2-24mm (wide-angle only), 18-55mm, 18-70mm, 70-300mm (all telephoto settings).

A technique using a zoom lens to instill a sense of motion in an inanimate object. The photographer sets a relatively slow shutter speed, such as 1/4 second and while the shutter remains open, quickly adjusts the zoom control to move through a wide range of focal lengths.