Glossary
ambient light The natural light in the scene. Also referred to as available light.
angle of view The amount of the scene in front of the camera that a specific lens sees. It is also referred to as field of view.
aperture The lens opening that the light passes through before reaching the sensor in the camera. The aperture can be adjusted by controlling the diaphragm, which is done by changing the f-stop. This is expressed as f/number — for example, f/5.6. The size of the aperture is one of the controls that determine the amount of light that can reach the camera’s sensor. The aperture also controls the Depth of Field. See Depth of Field.
aperture priority mode A semiautomatic exposure mode in which the photographer sets the aperture and the camera sets the shutter speed.
artificial light Any light that the photographer introduces into a scene.
aspect ratio The proportions of the image captured by the camera, calculated by dividing the width of the image by the image height.
auto mode In this mode the camera sets the shutter speed, aperture, and ISO to achieve the correct exposure.
autofocus The camera automatically adjusts the focus to keep the subjects in focus.
backlighting A method of lighting where the main light is placed behind the subject. Also see silhouette.
barrel distortion An effect that causes straight lines to bow outward, especially at the outer edges of the frame. This effect is more pronounced when using wide-angle lenses.
bounce light Light that is bounced off a surface before hitting the subject to create a more flattering light source. This is used mainly with a dedicated flash unit that can be aimed at a wall or ceiling.
buffer The camera’s built-in memory that is used as a temporary storage while the image data is being written to the memory card.
camera shake The small movements of the camera that can cause blurring, especially when the camera is being handheld. Slower shutter speeds and long focal lengths can contribute to the problem.
center-weighted metering The entire scene is metered, but a greater emphasis is placed on the center area.
color cast An overall look or predominant color that affects the whole image. Color casts are usually brought about by an incorrectly set white balance. See also cool and warm.
color temperature A way to describe the color of the light using the Kelvin scale. See also Kelvin.
colored gel filters Colored light modifiers that when placed between the light source and the subject, change the color of the light hitting the subject.
compression Reducing image file size by either removing information (lossy compression) or writing the information in a form that can be re-created without any quality loss (lossless compression).
compression distortion A photographic optical illusion that occurs when using a long focal length lens, where objects can appear closer together than they really are.
continuous auto focus mode A mode in which the camera continues to refocus while the shutter release button is held halfway down. This is the best focus mode for moving subjects.
contrast The difference between the highlights and the shadows of a scene.
cool A descriptive term for an image or scene that has a bluish cast.
dedicated flash A flash unit that is designed to work with your camera’s autoexposure modes.
depth of field (DOF) The area of acceptably sharp focus in front of and behind the focus point.
diffused lighting Light that has been scattered and spread out by being bounced off a wall or ceiling or shot through a semi-opaque material, creating a softer, more even light. Diffused lighting can also be sunlight shining through the clouds.
digital noise See noise.
exposure The amount of light that reaches the sensor.
exposure compensation A method of adjusting the exposure so that it differs from the metered reading.
exposure metering Using the light meter built into the camera to determine the proper exposure. See also metering modes.
f-stop A measure of the opening in the diaphragm that controls the amount of light traveling through the lens.
fast lens A description referring to the maximum aperture of a lens. Lenses with apertures of f/2.8 and higher are considered fast lenses. See also slow lens.
fill flash A method where the flash is used to fill in shadow areas to reveal details that would usually be lost.
filter A glass or plastic cover that goes in front of the lens. Filters can be used to alter the color and intensity of light, add special effects like soft focus, and protect the front elements of the lens.
flash A device that produces a short, bright burst of artificial light. The word flash can be used to describe the unit producing the light or the light itself.
flash sync The method by which the flash is fired at the moment the camera shutter is opened.
flat A description of an image or scene that has very little difference between the light values and the dark values. An image or scene with low contrast.
focal length The distance from the optical center of the lens when it is focused at infinity to its focal plane (sensor), described in millimeters (mm).
focal plane The area in the camera where the light passing through the lens is focused. In dSLRs, this is the digital sensor.
focus Adjusting the lens to create a distinct and clear image.
front lighting A method of lighting where the main light is placed directly in front of the subject.
gigabyte A unit of measurement equaling 1 billion bytes. Used in describing the capacity of the memory cards used in digital photography.
high contrast A description of an image or scene where the highlights and shadows are at the extreme differences in density.
high key A description of a photograph with a light tone overall.
histogram A basic bar graph that shows the distribution of tones in your image.
hot shoe The camera mount on top of the viewfinder that accepts flashes or flash triggers and accessories. Make sure that the flash or accessory is supported by your camera before you try to attach it.
ISO International Organization for Standardization. An international body that sets standards for film speeds. The standard is also known as ISO 5800:1987 and is a mathematical representation for measuring film speeds.
ISO sensitivity The light sensitivity of image sensors in digital cameras are rated using the standards set for film. Each doubling of the ISO makes the sensor twice as sensitive to light, meaning that in practical purposes, an ISO rating of 200 needs twice as much light as an ISO of 400.
JPEG Joint Photographic Experts Group. The most commonly used and universally accepted method for image-file compression. The JPEG is a lossy form of compression, meaning that information is lost during the compression. JPEG files have a .jpg file extension. See also lossy compression.
Kelvin Abbreviated with K, it is a unit to measure color temperature. The Kelvin scale used in photography is based on the color changes that occur when a theoretical black body is heated to different temperatures. See also color temperature.
LCD (Liquid Crystal Display) The type of display used on most digital cameras to preview your photos and display menus and shooting data.
light meter A device used to measure the amount of light in a scene. The readings from the light meter can be used to determine what settings produce a proper exposure. All recent cameras have a built-in light meter, which helps the camera determine which settings to use when not in manual mode.
lossless compression A form of computer file compression that allows the original data to be reconstructed without losing any of the information. This is useful when it is important that no changes are made to the information. See also compression and TIFF.
lossy compression A form of computer file compression that reduces the file size by removing data. The file will not match the original file exactly but will be close enough to be of use. This form of compression suffers from generation loss. Repeatedly compressing the same file results in progressive data loss and in photography, image degradation. See also compression and JPEG.
low key A term used to describe a photograph with a darker tone overall.
macro lens A specialty lens with the capability to focus at a very close range, allowing for extreme close-up photographs.
manual mode In this mode, the photographer determines the exposure by setting both the shutter speed and the aperture.
megapixel A description referring to the amount of pixels that a digital camera sensor has. Each megapixel is equal to 1 million pixels.
memory card The removable storage device that image files are stored on. It is the digital film in digital cameras.
metering modes The method the camera uses to determine what light to use in the metering process. See center-weighted metering, scene metering, and spot metering.
middle gray A tone that represents 18% reflectance in visible light. All reflective light meters are calibrated to give an average reading of 18% gray.
noise Pixels of random color introduced by either the amplification process used when shooting at high ISO or heat generated during long exposures in places where there should only be smooth color.
noise reduction Software or hardware used to reduce unwanted random pixels that appear when shooting at high ISO or during long exposures in digital images. See also noise.
overexposure Allowing more than the recommended amount of light to reach the sensor, causing the image to appear too light and with less detail in the highlights.
pixel A contraction of the words picture elements that describes the smallest unit that makes up a digital image.
prime lens A lens with a single unadjustable focal length.
RAW A file type that stores the image data without any in-camera processing.
rear-curtain sync The ability to fire the flash at the end of the exposure instead of at the beginning. This freezes the action at the end of the exposure.
red eye A condition that occurs when the flash is too close to the lens when photographing people. The light from the flash is reflected from the person’s retina, which is covered with tiny blood vessels; thus the red reflects back toward the camera’s lens.
red-eye reduction A flash mode that fires a short burst of light right before the photograph is taken, in the hopes of causing the subject’s pupils to contract, lessening the amount of light that can be reflected back.
saturation In color, it is the intensity of a specific hue.
scene metering The metering mode that reads the brightness in the entire frame and tries to match the data with a built-in database to get the best exposure. In the Canon system this is referred to as Evaluative metering; in the Nikon system this is called Matrix metering.
sharp A way to describe a well-focused image.
shutter A mechanism that controls the amount of light that is allowed to reach the sensor by opening for a specific length of time designated by the shutter speed.
shutter release button The button that when pressed causes the shutter to open and allow light to reach the sensor for the length of time programmed by the shutter speed.
shutter speed The amount of time that the shutter is open and letting light reach the image sensor.
side lighting A method of lighting where the main light source is to the side of the subject.
silhouette An image or scene where the subject is represented by a solid black object against a lighter background. See also backlighting.
slow lens A description referring to the maximum aperture of a lens. Lenses with a maximum aperture of f/5.6 are considered very slow. See also fast lens.
spot metering The only area that the camera uses to meter the light is a small area in the center of the scene. Some cameras will set the metering area to what focus point is being used.
stop A term of measurement in photography that refers to any adjustment in the exposure. When stop is used to describe shutter speed, a 1-stop increase doubles the shutter speed, and a 1-stop decrease halves the shutter speed. When stop is used to describe aperture, a 1-stop increase doubles the amount of light reaching the sensor, and a 1-stop decrease halves the light reaching the sensor. A stop can also be used to describe ISO settings, where a full stop either doubles or halves the ISO settings, making the camera either more or less sensitive to light. Most camera settings can be adjusted in 1/3 or 1/2 stops.
TIFF Tagged Image File Format. A lossless file format for images that is universally acceptable by image-editing software. See also lossless compression.
tonal range The shades of gray that exist between solid black and solid white.
tungsten light A light source that produces light with a color temperature of approximately 3200K. This is the type of incandescent light usually found in homes and produces a very orange color cast.
underexposure Allowing less than the recommended amount of light to reach the sensor, causing the image to appear too dark and have a loss of detail in the shadows.
warm A descriptive term for an image or scene that has an orange or red cast.
white balance An adjustment to how the camera records the colors to match the lighting of the scene. Setting the white balance correctly for the type of light in the scene will render the colors truer and result in a more natural looking image.
zoom lens A lens that has an adjustable range of focal lengths.