Photography terms starting with A

Animal and Bird Detection Focus & Depth of Field Subject recognition trained on animal anatomy, able to find and hold an eye on a creature rather than a human face.

Aperture Exposure & Metering f-stops (EV) The adjustable opening inside a lens that controls how much light passes through to the sensor, and with it the depth of field. N = f / D

Aperture Blades Optics, Lenses & Filters count The overlapping leaves inside a lens that form the iris, whose number and shape determine the geometry of the opening.

Aperture Priority Exposure & Metering A semi-automatic mode, marked A or Av, in which the photographer sets aperture and ISO while the camera chooses shutter speed.

Apochromatic Lens Optics, Lenses & Filters A lens corrected to bring three wavelengths of light to a common focus, rather than the two of a conventional achromat.

APS-C Cameras, Formats & Systems mm A sensor format roughly 23.5 by 15.6 millimetres, giving a crop factor of about 1.5× against full frame. Crop factor ≈ 1.5 (1.6 Canon)

APS-H Cameras, Formats & Systems mm An intermediate sensor format of about 28.7 by 19 millimetres, with a crop factor near 1.3×. Crop factor ≈ 1.3

Arca-Swiss Plate Cameras, Formats & Systems mm A dovetail quick-release plate standard, widely adopted so heads and plates from different makers interoperate.

Architectural Photography Genres, Movements & Theory Photography of buildings and structures, concerned with form, space and the accurate rendering of geometry.

Archive Files, Metadata & Workflow TB Long-term storage of completed work in a form intended to remain readable for decades.

Aspect Ratio Composition & Visual Design ratio The proportional relationship between an image's width and its height. Ratio = width : height

Aspherical Element Optics, Lenses & Filters count A lens element whose surface departs from a simple sphere, correcting aberrations that spherical glass cannot.

Astigmatism Optics, Lenses & Filters An aberration in which lines running radially and tangentially from the frame centre focus at different distances.

Astrophotography Genres, Movements & Theory seconds Photography of the night sky, from wide-field starscapes to magnified images of deep-sky objects. Rule of 500: t ≈ 500 / focal length

Asymmetrical Balance Composition & Visual Design A composition in which unequal elements are arranged so the frame still feels stable overall.

Aura Genres, Movements & Theory Walter Benjamin's term for the unique presence of an original artwork, which he argued mechanical reproduction dissolves.

Auto Exposure Bracketing (AEB) Exposure & Metering stops (EV) Shooting a rapid sequence of frames at different exposures around the metered value, as insurance or as source material for merging.

Auto Exposure Lock (AE-L) Exposure & Metering A control that freezes the metered exposure so the frame can be recomposed without the reading changing.

Auto ISO Exposure & Metering ISO A camera mode that lets the body select sensitivity automatically within limits the photographer sets, usually with a minimum shutter speed.

Auto White Balance Colour & Colour Management K A camera function that estimates the illuminant from the scene and sets white balance accordingly.

Autochrome Film, Darkroom & Historic Processes The first commercially successful colour process, using a screen of dyed potato starch grains over a black and white emulsion.

Autofocus Focus & Depth of Field A system that measures focus error and drives the lens to correct it automatically.

Automatic Servo Selection Focus & Depth of Field A mode, marked AF-A, in which the camera decides whether to lock focus or track continuously based on whether the subject appears to be moving.

AVIF Files, Metadata & Workflow MB An image format based on the AV1 video codec, offering high compression efficiency, wide gamut and high dynamic range support.

Terms starting with A