glossary - a
ABERRATION:(1) Something that prevents light from being brought into sharp focus, disenabling the formation of a clear image.
(2) Lens flaw - the inability of a lens to reproduce an accurate, focused, sharp image.
ABSORPTION:Occurs when light is partially or completely absorbed by a surface, converting its energy to heat.
ABSTRACT:In the photographic sense, an image that is conceived apart from concrete reality, generally emphasizing lines, colors and geometrical forms, and their relationship to one another.
A fitting generally located on top of a camera to which accessories (such as a flash unit) are attached.
ACHROMATIC:Free from chromatic aberration. An achromatic lens is able to transmit light without separating it into colors.
ACTIVE AUTOFOCUS:A radar-like autofocus system that (actively) sends out a beam of light to determine focusing distance. Passive Autofocus.
See Also: Passive Autofocus.
A measure of the sharpness with which the film can produce the edge of an object.
The perception of depth or distance caused by atmospheric haze and its effect on tonal change in an image.
Photography conducted above ground, commonly understood to be picture-taking from an aircraft.
Above ground; in the air. Also casually refers to a picture taken from the air, as in an aerial or an aerial photograph.
Autofocus Lock - Causes the camera to stop automatically focusing. AF lock is typically used when the subject is outside of the viewfinders autofocus sensor(s). The photographer first aims the camera so that subject comes automatically into focus, locks in that focus setting using AF lock so that autofocus is temporarily disabled, then recomposes the image and takes the picture.
Gentle movement of liquid photo-processing chemicals (developer, stop-bath, fixer) during processing of film or paper in order to achieve uniform results.
Existing light surrounding a subject; the light that is illuminating a scene without any additional light supplied by the photographer. Available light and existing light are two other terms that mean the same thing.
A lens that compresses a wide-angle of view into a standard frame.
ANGLE OF INCIDENCE:
Light striking a surface is called incident light. It becomes reflected light when it reflects from the surface. The angle of incidence is the angle at which the incident light strikes the surface, and is measured from a line that is perpendicular to the surface (called the normal).
ANGLE OF VIEW:
Also known as the Field of view, FOV and the Angle of the field of view, it is the extent of the view taken in by a lens. Focal length of a lens, in conjunction with film size, determines the angle of view. A standard lens has an angle of view equal to the diagonal of the film, which is generally around 52 or 53.
APERTURE:An iris-like device in a lens that opens and closes to control the amount of light allowed to reach the film.
APO:A lens designation that stands for "Apochromatic". Refers to a lenss ability to bring all colors of the visible spectrum to a common plane of focus, within close tolerances. Used to indicate a lens with superior color correction
Often shortened to APO, means corrected for spherical and chromatic aberration. Lenses that are apochromatic cause all visible light wavelengths to focus on the film plane. Lenses that are not corrected for chromatic aberration tend to focus red, green and blue wavelengths on different planes.
The handling, treating and storage of photographic materials in a manner that lessens their deterioration from aging or from reaction to other materials.
ARTIFACT:Misinterpreted color value assignation for a pixel in a digital image. Usually happens as part of a compression or decompression process
Illumination that comes from a man-made source, such as electronic flash.
The now defunct film speed rating system of the USA Standards Institute, which was formerly called the American Standards Association - hence the acronym ASA. The ASA system has been replaced by the more universal ISO system.
ASPHERIC:Common lens designation. Refers to lens element with one or two non-spherically shaped surfaces. Such surfaces can compensate for lens aberrations, often allowing for smaller and lighter-weight lenses with resolving power and superior imaging characteristics of larger lenses.
AUTO BACKLIGHT CONTROL:A metering feature that automatically recognizes a subject in shadow (that is, backlit) and increases the exposure to compensate.
AUTO BRACKETING CONTROL (ABC):A feature of some mid- and high-end single-lens-reflex camera that automatically produces three of more different exposures with one press of the shutter release. Typically, one exposure is made at the metered exposure setting, the others at user-specified intervals above and below the meter reading.
AUTO EXPOSURE BRACKETING (AEB):
See Also: Auto Bracketing Control.
AUTO EXPOSURE LOCK (AEL):A metering feature that holds exposure settings even if lighting conditions change. Useful when background lighting changes, but the subject
AUTOFLASH:A camera operation mode in which the camera automatically fires its flash when its programming suggests flash is needed, such as in low-light situations.
An automatic aperture remains fully open until the shutter is released, at which time it closes down to the pre-set aperture size in order for the picture to be properly-exposed. An automatic lens has an automatic aperture.
Camera that adjusts the aperture and shutter speed automatically using its built-in exposure meter.
A lens that remains open at its widest aperture until the shutter is released, regardless of the aperture setting. Such a lens facilitates focusing with through-the-lens cameras since the maximum amount of light reaches the viewfinder. When the shutter is released, the aperture automatically stops down to its pre-set opening so that proper exposure is made, then returns to a wide-open position until the next time.
Existing light surrounding a subject; the light that is illuminating a scene without any additional light supplied by the photographer. Ambient light and existing light are two other terms that mean the same thing.