Exposure Value (EV)

The exposure value represents a combination of shutter speed and aperture setting (f-number), independent of sensitivity (ISO) setting. Since the camera settings for a given EV takes no account of the sensitivity setting, it is normal to adjust the EV to take sensitivity into account, and the Readout value is an EV adjusted for an ISO speed of 100.

Photographic Expoosure (EV)

The combination of camera settings that result in a particular exposure value adjusted for a particular sensitivity is given by the equation:

  EV = log2 (F2/(ISO * s))

  F = f-number
  ISO = ISO sensitivity.
  s = shutter time in seconds.

The measured EV value is an exposure recommendation based on either the incident light (ambient illuminance measurement) falling on the subject of the photograph,
Incident Light Measurement

or the reflected light (spot emission luminance measurement) from the subject towards the camera,
Reflected Light Measurement
both of which are computed according to the ISO 2720 method. The appropriate calculation is chosen automatically based on the instrument measurement mode.

Index       Quick Start