Exposure & Metering — 60 Terms Defined

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 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.

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.

Base ISO Exposure & Metering ISO The sensitivity at which a sensor is read out with no amplification, delivering its maximum dynamic range and cleanest files.

Bellows Extension Factor Exposure & Metering stops (EV) The extra exposure required when a lens is racked far forward for close focus, spreading its light over a greater distance. Factor = ((v) / f)²

Blown Highlights Exposure & Metering Bright areas recorded at maximum value across all channels, rendering as featureless white that no processing can restore.

Bulb Mode Exposure & Metering seconds A shutter setting, marked B, that keeps the shutter open for as long as the release is held down.

Centre-weighted Average Metering Exposure & Metering A metering pattern that averages the whole frame while giving most of the weight — typically 60 to 80 per cent — to the central area.

Clipping Exposure & Metering The loss of tonal information when values are pushed past the maximum or minimum a file can encode.

Crushed Blacks Exposure & Metering Shadow areas pushed to pure black so that separation between dark tones is lost.

Dynamic Range Exposure & Metering stops (EV) The span between the brightest and darkest tones a camera can record in a single frame while keeping usable detail at both ends. DR = log₂(full-well / read noise)

Effective Aperture Exposure & Metering f-stops (EV) The working f-number of a lens once it is focused close, which is always darker than the marked aperture because the lens is extended away from the sensor. N_eff = N × (1 + m)

Equivalent Exposure Exposure & Metering stops (EV) Any different combination of aperture, shutter speed and ISO that yields identical image brightness. N₁²/t₁ = N₂²/t₂

Evaluative (Matrix) Metering Exposure & Metering A metering pattern that divides the frame into zones, compares their brightness against a database of scene types, and infers the photographer's intent.

Exposing to the Right (ETTR) Exposure & Metering stops (EV) The technique of exposing as brightly as possible without clipping, then darkening in processing to maximise signal-to-noise ratio.

Exposure Exposure & Metering lux-seconds (lx·s) The total amount of light that reaches the sensor or film, set by the combination of aperture, shutter speed and the scene's brightness. H = E × t

Exposure Compensation Exposure & Metering stops (EV) A deliberate offset applied to the camera's metered reading, expressed in stops, to make an image brighter or darker than the meter suggests. Setting = Metered EV − Compensation

Exposure Latitude Exposure & Metering stops How far an exposure can miss the ideal and still produce an acceptable image after processing.

Exposure Simulation Exposure & Metering A live-view or electronic-viewfinder mode that displays the scene at the brightness the current settings will actually record.

Exposure Triangle Exposure & Metering stops The teaching model that links aperture, shutter speed and ISO as three interdependent controls, where changing one requires compensating with another. Aperture ↔ Shutter ↔ ISO

Exposure Value (EV) Exposure & Metering EV A single number describing every combination of aperture and shutter speed that produces the same exposure. EV = log₂(N² / t)

Extended ISO Exposure & Metering ISO ISO settings outside a sensor's native range, marked with an L or H prefix, that are produced by digital manipulation rather than analogue gain.