Factual piece of information (as measurements or statistics) used as a basis for reasoning, discussion, or calculation. Information output by a sensing device or organ, it includes both useful and irrelevant or redundant pieces of information that must be processed to be meaningful in a decision making process. Information in numerical form that can be digitally transmitted and/or processed. "Don't confuse me with the data, give me information to make decisions".

Dark material used to cover the photographer's head and the ground-glass-viewing screen on large format cameras.

Thin, flat piece of metal or plastic, which protects unprocessed film from light exposure.

The distance between the farthest and nearest points which are in focus. This can also be identified as the zone of acceptable sharpness in front of and behind the subject, to which the lens is focused on. DOF varies according to numerous factors such as lens focal length, aperture, shooting distance, etc.

Where straight lines are not rendered perfectly straight in a photograph. Two types of distortion exist: barrel and pincushion.

A glass developed and trademarked by Nikon Corporation, used in telephoto lenses to offer superior sharpness and color correction by minimizing chromatic aberration. These lenses are resistant to temperature changes, preventing focus shift problems in lenses that use calcium fluorite crystal elements. Fluorite cracks easily and is sensitive to temperature changes that can adversely affect focusing by altering the lens’ refractive index. Super ED glass is a new type, used together with ED glass in some lenses achieves an even higher degree of freedom from chromatic aberration.

The amount of light that reaches a film frame or a digital sensor or the combination of f-stop (light intensity) and shutter speed (duration) that controls the amount of light reaching the film or sensor. Also used to describe an exposed piece of film.

Photosensitive material used in a camera to record an image. Made from a thin, transparent base coated with light sensitive chemicals.

Transparent lens attachment used to modify the light coming into a lens, to change the color, or other characteristics of an image. They are used both on the camera and in the darkroom.

Super wide angle lens. Angle of view can approach 180 degrees. Nearly infinite depth-of-field.

A camera with a non-removable, non-zoom lens with unchangeable focal length. 
A prime lens.

Reflected light; from lens elements, sun, metal, etc. Appears as non-uniform haze or bright spots on the film or digital frame, often taking the shape of the aperture, generally caused from shooting towards the light source. The use of uncoated filters makes a lens more prone to flare; often results in an overall reduction of image contrast. The always-on use of a lens shade is also recommended.

Artificial light source. Usually camera-mounted speedlights (like the SB-28, SB-80DX) but also larger studio models called strobes.

The shutter speed that corresponds to the proper timing of the flash. Any faster and the shutter won't be open for the duration of the flash. Any shorter and subject movement might cause blur.

The distance between the back lens element and the focal plane. In 35mm format, lenses with a focal length of approximately 50mm are called normal (standard), lenses with approximately 35mm or less are called wide-angle, and lenses with a focal length of more than approximately 70mm are called telephoto lenses.

The point on the optical axis where light rays form a sharp image of a subject. An ideal lens would allow light rays to diverge from a subject parallel to the optical axis and converge to a point when they pass through the lens.

To move the lens, or film or digital sensor, in relation to the focal plane in order to record a sharp image on the film/sensor. (Can't forget Contax where the film actually moves for AF operation versus the lens.)

Three basic types of focus modes exist for Nikon AF cameras: Single servo AF (S), Continuous servo AF (C) and Manual AF (M).

Refers to Ground Glass. Usually on large format cameras, a piece of frosted glass at the focal plane where the lens projects an image that can be used for focusing and composition.

Advanced feature through which a camera's microprocessor (computer) analyzes a moving subject's speed, anticipates the position of the subject at the exact moment of exposure, and focuses the lens based on this information.

Can mean either the size of the camera or the size of the film or sensor. For camera, sizes there are APS, 35mm, medium and large format. For film format there is APS, 35mm, 645, 6x6, 6x7, 6x9, 4x5, 5x7, 8x10, etc. In digital photography, DX, 35mm size, 645 and 6x6.

Refers to the contrast rating of black and white enlargement papers. Zero is the lowest contrast and 5 is the maximum contrast.

Exposed and processed silver halides on the film emulsion that turn black and form miniature "grain" that make up the image on a piece of film. The equivalent efect at high ISO in digital photography -which is grainless- is "noise".

Frosted glass used as a viewing mechanism in cameras without prisms. The glass is placed so that the lens projects the image against the glass for focusing and composition purposes.

A number used to describe the output capacity of a flash. Usually measured using an ISO sensitivity or speed of 100. Divided by the distance from flash to subject it yields aperture.