Third Stop
A one-third-stop increment, the fine adjustment step most digital cameras use for aperture, shutter speed, ISO and exposure compensation.
Formula / rule
⅓ stop = ×2^(1/3) ≈ ×1.26
Measured in
stops (EV)
In depth
Thirds were adopted because they are the smallest change most people can reliably see in a print, and because the classic film speed series already ran in thirds. The intermediate aperture markings — f/3.2, f/3.5 between f/2.8 and f/4 — are thirds, as are shutter values like 1/160 and 1/200.
Examples in practice
Dialling +⅔ EV of exposure compensation lifts a backlit portrait's face without pushing the sky into clipping.