Sophie Vidal

Exposure

The amount of light reaching the sensor, measured in stops (EV) — one stop doubles or halves the light. Correct exposure stays within the 12-14 stops of dynamic range of modern sensors and depends on aperture, shutter speed and ISO.

Focus

The plane of optical sharpness — a slice typically 0.5 mm to 50 cm deep depending on aperture and focal length. Precise focus makes the main subject sharp, while the background can be intentionally blurred (bokeh) to isolate it.

White Balance

A setting that corrects color cast based on the light source, measured in Kelvin (1800 K candle, 3200 K tungsten, 5500 K daylight, 8000 K shade). Incorrect WB gives overly warm (orange) or cool (blue) tones.

Digital Noise

Parasitic grain visible in the image, especially in dark areas. It mainly appears from ISO 1600 on full-frame, 400 on smartphones, and on exposures longer than 1 s. Two families: luminance noise (grain) and chrominance noise (colored spots).

Aperture

The diameter of the lens diaphragm opening, expressed in f-stops. A small number (f/1.8) = wide opening = more light and shallow depth of field (blurred background). A large number (f/16) = narrow opening = less light and deep depth of field (everything sharp).

ISO

The sensor's sensitivity to light. Low ISO (100-400) produces a clean image but requires more light. High ISO (1600+) allows shooting in low light but introduces digital noise.

Shutter Speed

The duration the sensor is exposed to light. A fast speed (1/1000s) freezes motion. A slow speed (1/30s or less) can create motion blur, useful for waterfalls or light painting.

Focal Length

The optical distance of the lens expressed in mm. A wide-angle (< 35mm) captures a broad field with distortion. A telephoto (> 85mm) compresses perspective and brings distant subjects closer. The standard focal length (50mm) is closest to human vision.

Depth of Field

Acceptably sharp zone around the focal plane (from a few mm at f/1.4 in macro to several meters at f/11 on a wide-angle). Three governing factors: aperture, focus distance, focal length. Key tool to isolate a subject or keep everything sharp in landscape.

Bokeh

Aesthetic quality of background blur (≠ depth of field, which measures the quantity). Japanese word ボケ popularized in 1997. Depends on the diaphragm blade count and optical design.

Exposure Triangle

System of three variables (aperture, shutter, ISO) that together determine exposure. Changing one by a stop forces compensation on the other two to keep the same amount of light.

Hyperfocal Distance

Focus distance at which depth of field extends from half that distance to infinity. Key tool for landscape and street zone-focusing.

Histogram

Statistical chart with luminance levels (0 black → 255 white) on the X axis and pixel count on the Y axis. Objective tool to evaluate exposure, more reliable than the rear screen.