OTF

Definition: Off-The-Film: adjective: ~ metering: variant of through-the-lens metering in which the sensor is positioned to look at the film gate. * Strictly, OTF is applied to flash metering in that the exposure reading for the flash-gun is taken off light reflected off the surface of the exposed film during shutter-run. * May be used to refer metering systems that take their reading off the shutter curtain which is suitably painted to reflect light. Olympus the first OTF was pioneered by Olympus in their OM-2 camera as a result of their discovery that different films -- black & white or colour of various types -- surprisingly have nearly identical reflectance (i.e. reflect nearly exactly the same proportion of incident light). Metering off the shutter curtain is regarded as too crude for modern auto-focus SLRs but is effectively implemented in the Leica M6 series of cameras.

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