A feature on some cameras that enables you to automatically shoot a sequence of shots of the same scene at slightly different shutter speeds (or aperture settings) from the ‘correct exposure’. This feature can be used if there’s some doubt that the meter reading is accurate for a particular subject. It can also be used to shoot a sequence that’s combined into one high dynamic range image. See HDR. Other auto-bracketing features available on some cameras include automatic flash, ISO or white balance bracketing.
Photography achieved by attaching a camera to a telescope and concerned with recording images of astronomical objects in the night sky such as stars, planets and the moon. Astrophotography can also be used to record astronomical objects invisible to the human eye by using long exposures.
A lens element that has a surface that isn’t perfectly spherical. All camera lenses are made up of a number of individual lenses or elements. Many of these elements are spherical, as if cut from a sphere. A-spherical elements are less rounded and are used in wide-angle and wide-aperture lenses to help provide distortion-free images.
The existing light in a particular scene, which may be sunlight, moonlight or an artificial light already providing illumination. It excludes any light source added by the photographer, such as flash or studio lighting.
This term refers to a range of photographic processes, mostly dating from the late 19th and early 20th century, which devotees continue to use for their unique qualities. They include the daguerreotype, gum bichromate, cyanotype, salt print, bromoil, platinum, and palladian processes.
A type of photographic print invented in 1850 by Frenchman Louis Désiré Blanquart-Evrard (1802-1872). It consists of a sheet of paper coated in egg white (albumen) and salt, then dipped in a light-sensitive silver nitrate solution. The paper, when dried, is overlaid with a glass negative and exposed to the sun. The albumen print was widely used until the late 19th century.
This is a system used by some cameras and flashguns to assist autofocus in low light. A pattern of red light is projected on to the subject, which aids the contrast-detection autofocus to adjust the lens correctly.
AF Stands for autofocus, a function first introduced on cameras in the late 1970s, in which the lens is adjusted automatically to bring the designated part of the image into sharp focus. Almost all modern lenses for digital SLRs have AF, which is achieved via one or more sensors and a motor either integrated into the lens itself or the camera body.
An autofocus (or AF) optical system uses a sensor, a control system, and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication. Autofocus methods are distinguished by their type as being either active, passive or hybrid variants.
Autofocus systems rely on one or more sensors to determine the correct focus. Some AF systems rely on a single sensor, while others use an array of sensors. Most modern SLR cameras use through the lens optical sensors, with a separate sensor array providing light metering, although the latter can be programmed to prioritize its metering to the same area as one or more of the AF sensors.
through-the-lens optical autofocusing is now often speedier and more precise than can be achieved manually with an ordinary viewfinder, although more precise manual focus can be achieved with special accessories such as focusing magnifiers. Autofocus accuracy within 1/3 of the depth of field (DOF) at the widest aperture of the lens is common in professional AF SLR cameras.
Automatic exposure lock. This is a push-button control that enables you to select the part of the scene from which the camera takes its meter reading, and then lock this setting while the image is re-framed for better composition. The auto-exposure lock (AE-L) function on a DSLR camera lets you physically lock the exposure reading from anywhere in the scene. You can use it on its own or at the point where you focus the image. Just about all DSLR cameras have an auto exposure lock button.
An abbreviation for automatic exposure. This camera feature enables the user to determine the shutter speed and aperture for an image, usually via a TTL (through-the-lens) exposure meter. Automatic exposure mode (also called automatic exposure and abbreviated as AE) is a standard feature on digital cameras that will automatically determine the correct exposure for pictures without any user input other than to select the AE option before taking a picture.