Sensibility versus definition

Started Jan 7, 2015 | Questions thread
Mark S Abeln
Mark S Abeln Forum Pro • Posts: 19,447
Re: Sensibility versus definition

PeterBM wrote:

Why, for the the same camera, have i the same sensibility for different image definitions?

For example for a given scene:

- full definition 4000x3000 pixels at 200 ISO F4.0 good time is 1/100s

- 1/4 definition 2000x1500 pixels at 200 ISO F4.0 good time is still 1/100s. Why isn't it 1/400s ?

Exposure is defined relative to unit area. That’s why the same exposure will basically work for all cameras — without regard to sensor or film size — as long as they have the same ISO rating. Handheld light meters works with any camera.

“In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film, as determined by shutter speed, lens aperture and scene luminance. In digital photography "film" is substituted with "sensor". Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.”

http://en.wikipedia.org/wiki/Exposure_(photography)

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