Exposure value (EV100)

Exposure value summarizes an aperture and shutter-time combination at ISO 100.

N is f-number and t is shutter time in seconds. A one-stop change corresponds to a factor of two in the quantity inside the logarithm.

Relative optical exposure

Ignoring lens transmission and scene radiance, relative optical exposure scales with:

Photivra keeps exposure relationships separate from sensor noise and does not treat ISO as a shortcut for physical light collection.

Model limits

These relations do not include lens T-stop, vignetting, spectral transmission, scene radiance, clipping, sensor gain calibration, or a complete imaging pipeline.