Glossary

AE

Automatic Exposure; Three kinds are available: programmed auto exposure, aperture-priority auto exposure and shutter-priority auto exposure.
 

AF-I (Nikon)

Lens with built-in autofocus drive motor. CPU is also built in. AF-I Nikkor lenses send information on distance to the camera body and are classified as D-type AF Nikkor lenses.
 

AI (Nikon)

Automatic index; Nikon's system for telling the camera's exposure meter what the lens' maximum aperture is.
 

AI/S (Nikon)

Automatic index/Shutter; Nikon's lens mount permitting automatic operation in shutter-priority and program auto-exposure systems.
 

Aperture

The variable opening produced by the iris-diaphragm through which light passes to the film plane. Measured in f/stops.
 

Aperture Priority

Autoexposure systems wherein the photographer selects the aperture and the camera selects the appropriate shutter speed.
 

APO

Apochromatic; a type of lens which focuses different wavelengths of light on the filmplane for improved image sharpness. Especially useful in telephoto lenses. (Chromatic aberration is corrected).
 

ASA

American Standards Association; (see ISO).
 

B (Bulb)

At the B setting, the shutter remains open as long as the shutter release button remains fully depressed.
 

Bracketing

Take a series of pictures at different exposures.
 

Coating

A layer or multiple layers of thin anti-reflective materials applied to the surface of lens elements to reduce light reflection (flare) and increase the amount of transmitted light.
 

Close-Up

The general term for pictures taken at relatively close distances, from 1/10 life-size (1:10) to life-size (1:1).
 

Depth of Field

The range of acceptably sharp focus in front of and behind the distance the lens is focused on.
 

Diaphragm

A series of metal "blades" that can be manipulated to form a larger or smaller opening through which the light is admitted.
 

Digital Imaging

The new evolution of the art of photography where images are scanned into an electronic format and then "processed" with software such as Adobe Photoshop.
 

DIN

International Standard (see ISO).
 

DX-Coding

Code printed on film cartridges providing most new cameras with film speed information.
 

Element

One piece of glass comprising the internal optics of a lens. (See Group).
 

EOS (Canon)

Electronic Optical System; Canon's current line of autofocus cameras and accessories.
 

E-TTL (Canon)

Evaluative, through-the-lens flash metering.
 

EV

Exposure Value; A number that represents available combinations of shutter speed and aperture offering the same exposure effect when scene brightness remains the same. Each EV number can be applied to various shutter speed and aperture combinations.
 

Exposure

Light striking a sensitized material (film or paper emulsion).
 

Exposure Compensation

Modifying the shutter speed and/or lens aperture recommended by the camera's light meter in order to produce special creative effects or to meet special requirements.
 

Fill-Flash

Exposure consisting of a combination of flash and "available light" balanced to produce a pleasing mix of the two.
 

Fisheye

An ultra-wide angle lens which purposely introduces barrel distortion so straight lines near the edges of the frame appear to curve out.
 

Flare

Image degradation caused by stray light which passes through the lens but is not focused to form the primary image. Often caused by light bouncing off internal air-to-glass surfaces.
 

Focal Length

The distance from the optical center of a lens to the image plane when the lens is focused to infinity.
 

Golden Rectangle

An image ratio (width vs the height) that makes the most pleasing, balanced impression on the viewer. Panoramics are long and skinny; square negatives often make it hard for the viewer to recognize the central focus of a composition. A 35mm format is pretty close to a golden retangle.
 

Group

Two or more elements cemented together within a lens. Lenses are described as having a certain number of elements in a certain smaller number of groups.
 

Guide Number

The power of a flash in relation to ISO film speed. Guide numbers are quoted in either meters or feet. (To convert from meters to feet, multiply the metric number by 3.3). Guide numbers are used to calculate the f/stop for correct exposure as follows: f/stop=guide number/distance.
 

Hot Shoe

A mounting device, usually built onto the top of a camera, that enables a flash unit, or speedlight, to be mounted on and triggered by the camera.
 

ISO

International Standards Organization; the number represents the film's sensitivity to light. A higher ISO number indicates the film is more sensitive and requires less light for a proper exposure.
 

Latitude

The variance from "proper" exposure which will still provide acceptable results.
 

Matrix

Autoexposure metering where the camera sets both aperture and shutter speed according to data stored in the camera's built-in memory, comparing the scene to be photographed to reference scenes.
 

Macro Focusing

Macro focusing, applied to zoom lenses, moves the lens group(s), enabling the lens to focus closer than the normal focusing distance from close-up shooting.
 

Photography

From the Greek the means "painting or writing with light."
 

Resolution

A word with many meanings. In digital imaging, it most often refers to the number of pixels per inch in an image file. It can also refer to printer resolution, digital camera CCD resolution, etc. In traditional photography, if refers to the ability of a lens or photographic material to reproduce small details and is measured in lines per millimeter.
 

Shutter Speed

How fast the camera's shutters open. Determines how long the film is exposed for.
 

Shutter Priority

When the photographer selects the shutter speed and the camera automatically sets the corresponding aperture.
 

SLR

Single Lens Reflex; a camera with one lens (as opposed to Twin Lens Reflex like the Rolleiflex) that involves a mirror and prism that the viewer looks through (as opposed to a point and shoot or rangefinder where the viewer looks through a separate viewfinder.
 

Sunny-16 Rule

A guideline that states that you can expose a normal scene, lit by bright sunlight, at an aperture of f16 and a shutter speed equivalent to the film speed (ISO or ASA) being used.
 

TTL

Through-the-lens; commonly used when referring to metering through the lens as opposed to via a separate meter. Effective for fill-flash and other tricky lighting situations.
 

Rule of Thirds

The rule states that an image should be imagined as divided into nine equal parts by two equally-spaced horizontal lines and two equally-spaced vertical lines, and that important compositional elements should be placed along these lines or their intersections.   Further Information and some more.
 

USM (Canon)

UltraSonic Motor; Canon's fastest, quietest autofocus lens mechanism.
 

 


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