Exposure & Metering — 60 Terms Defined

RGB Histogram Exposure & Metering Three separate histograms, one per colour channel, revealing clipping that a combined luminance histogram would hide.

Shutter Priority Exposure & Metering A semi-automatic mode, marked S or Tv, in which the photographer sets shutter speed and ISO while the camera chooses aperture.

Shutter Speed Exposure & Metering seconds The length of time the shutter stays open, controlling both total exposure and how much subject or camera movement is recorded as blur. t = 1 / denominator

Spot Metering Exposure & Metering A metering pattern that reads only a small circle, usually one to three per cent of the frame, ignoring everything around it.

Stop Exposure & Metering stops (EV) The fundamental unit of exposure change: one stop doubles or halves the amount of light reaching the sensor. 1 stop = ×2 or ÷2 light

Sunny 16 Rule Exposure & Metering stops (EV) A field estimate stating that in bright, direct sunshine, correct exposure is f/16 with a shutter speed of one over the ISO. t = 1/ISO at f/16

T-stop Exposure & Metering T-stops A measured aperture value that accounts for the light a lens actually transmits, rather than the geometric ratio an f-number implies. T = N / √(transmittance)

Third Stop Exposure & Metering stops (EV) A one-third-stop increment, the fine adjustment step most digital cameras use for aperture, shutter speed, ISO and exposure compensation. ⅓ stop = ×2^(1/3) ≈ ×1.26

Time Mode Exposure & Metering seconds A shutter setting, marked T, that opens the shutter on one press of the release and closes it on a second.

Underexposure Exposure & Metering stops (EV) An exposure that records less light than the scene needs, producing dark, noisy shadows and muddy colour.

Zebra Stripes Exposure & Metering IRE or % A live-view overlay of diagonal stripes marking areas above a set brightness threshold, used to judge exposure before the shutter fires.

Zone System Exposure & Metering zones (1 zone = 1 stop) Ansel Adams's method of dividing the tonal range into eleven zones and placing chosen subject tones deliberately on that scale. Zone V = metered value