Glossary

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Effective ISO

Numerical value describing the sensitivity of a sensor as defined by ISO 12232 standard. Read more

EV (exposure values)

Combination of a camera exposure time and lens aperture giving the same sensor exposure. By convention, EV is expressed on a logarithm 2 basis, so doubling the sensor exposure corresponds to EV+1.

Exposure

Amount of light that falls on a sensor or a film during the exposure time, expressed in lux.sIt is dependent upon scene luminance, aperture and exposure time.

Exposure time

Time during which a sensor acquires ambient light.

Extrapolation

Operation that creates values from a sequence of known values.

F-stop

Field of view

Angular extent of the part of the scene viewed by a camera.

Filter

Optical component that removes some light, either to lower intensity (neutral filters) or to change the light spectrum (colored filters).

Flare

Optical artifact coming from reflection on lenses, usually visible with a bright light source (such as the sun). Can lead to “ghosts” of the light source or “veiling glare” (loss of contrast) that creates a foggy effect on the image.

Focal plane

Plane perpendicular to the optical axis at which an object at infinity is in focus.

Focus distance

Distance at which objects are in focus.

Frame

Choosing the part of a scene that is visible in a photo.

Full-field sensors

By reference to silver-halide photography, sensors whose dimensions are 36x24mm.

Gain

Multiplicative numerical value used to amplify a signal.

Grain, graininess

Appearance of the noise in a homogeneous part of an image.

Gray levels

Numerical values related to the amount of light a pixel receives.

Gray patch

Uniform part of a color-neutral chart.

Gretag Macbeth Color Checker

Target commercialized by Xrite, containing 24 colored patches, commonly used for color reproduction testing.

Highlights, burned

Exposure levels close to or beyond saturation. Burned areas appear white and uniform.

Hue

Perceptual property of colors like red, blue, yellow...