Base Exposure
The Exposure Triangle
Exposure is controlled by three factors: aperture (controls light and depth of field), shutter speed (controls light and motion), and ISO (sensitivity and noise). Changing one requires adjusting another to maintain the same brightness.
Formula: EV = log₂(N² / t) where N is f-number and t is shutter speed in seconds, calibrated at ISO 100.
1 Stop = 2× the Light
- Open aperture 1 stop (f/5.6 → f/4) = 2× more light, double shutter speed to compensate
- Double ISO (100 → 200) = 2× more sensitivity, halve shutter speed or close aperture 1 stop
- Double shutter speed (1/250 → 1/500) = 2× less light, open aperture or double ISO