dark current

Definition: Unstable reading given by a CCD when powered to operating voltage but when no light falls on it, thus causing noise in the signal of e.g. digital cameras. * Worsens with greater sensitivity of chip and at higher temperatures.
Cool and wide
Dark current is enough of a problem that high-resolution backs and scanning backs carry their own refrigeration unit. But don't complain: the result of a chilled sensor is great dynamic range: these backs can record high highlights to deep shadows, covering dynamic ranges which far exceed even that of colour negative film. Obviously they're practical only with medium-format and larger cameras.

Related Terms: CCD, noise

Previous Term: dark box  Next Term: D-line

Type a photography term below to find its definition: