Glossary

The words that get used as though everybody already knows them.

Aperture: The adjustable opening inside a lens that controls how much light reaches the sensor, and how much of the scene is sharp.
Backlighting: Light coming from behind the subject, towards the camera. It separates a subject from its background and reliably fools a meter.
Blue hour: The period before sunrise and after sunset when the sun is below the horizon and the remaining light is even and blue.
Bokeh: The quality of the out-of-focus areas in a photograph — not how much blur there is, but what it looks like.
Camera shake: Blur across the whole frame caused by the photographer's own movement during the exposure.
Clipping: Where a photograph has gone to pure white or pure black, losing all detail in that area permanently.
Colour temperature: A measurement of the colour of light in kelvin. Lower numbers are orange, higher numbers are blue.
Contrast: The difference between the light and dark parts of a photograph.
Crop factor: The number describing how much smaller a sensor is than full-frame, and therefore how much narrower the view through the same lens.
Depth of field: The band of distance, in front of and behind the focus point, that comes out acceptably sharp in a photograph.
Dynamic range: The span between the darkest and brightest things a sensor can record in one exposure without losing detail at either end.
Exposure compensation: A control that tells the camera its meter reading is wrong, and by how many stops, without leaving automatic mode.
Exposure triangle: The relationship between aperture, shutter speed and ISO — the three controls that together decide how bright a photograph is.
f-number: The number that describes an aperture, written f/2 or f/8. It is the focal length divided by the width of the opening.
Fill light: Light added to the shadow side of a subject to reduce contrast, without becoming the main light.
Flash: A brief, bright artificial light fired at the moment of exposure. Useful for filling shadows as often as for lighting a dark scene.
Focal length: A lens's angle of view, measured in millimetres. Shorter takes in more of the scene; longer magnifies a narrower slice of it.
Focus: Setting the lens so that a chosen distance is rendered sharply.
Full-frame: A sensor the same size as a frame of 35mm film, 36 by 24 millimetres. The reference format most photography writing assumes.
Golden hour: The hour or so after sunrise and before sunset, when sunlight is low, warm and soft.
Histogram: A graph of how many pixels fall at each brightness, from black on the left to white on the right.
Hyperfocal distance: The focus distance at which everything from half that distance to infinity comes out acceptably sharp.
ISO: How strongly the camera amplifies the signal from its sensor. Higher values let you shoot in less light, at the cost of visible noise.
JPEG: A finished, compressed image file produced by the camera from the sensor data, ready to share.
Leading lines: Lines in a scene — roads, fences, shadows, edges — that draw the eye through the frame towards the subject.
Macro: Photography at very close range, where the subject is rendered at or near life size on the sensor.
Metering: How a camera measures the light in a scene in order to choose an exposure — and the assumption that makes it get some scenes wrong.
Middle grey: The tone a light meter assumes a scene averages out to — a grey reflecting about 18% of the light falling on it.
Motion blur: The smear left when a subject moves across the frame while the shutter is open.
Negative space: The empty area around a subject. Used deliberately, it isolates the subject and gives a photograph somewhere to breathe.
Noise: The speckled texture that appears in a photograph, most visibly in the shadows, when the sensor's signal is amplified.
Panning: Following a moving subject with the camera during the exposure, so the subject stays sharp and the background streaks.
Prime lens: A lens with one fixed focal length and no zoom. Usually sharper, usually with a wider maximum aperture, and always cheaper for the same quality.
Quality of light: How abruptly light falls off into shadow. Hard light gives sharp-edged shadows; soft light gives gradual ones.
RAW: An image file holding the sensor's data more or less as recorded, before the camera turns it into a picture.
Reciprocal rule: A rule of thumb: to hand-hold sharply, use a shutter speed at least as fast as one over the focal length.
Rule of thirds: A composition guide that divides the frame into a three-by-three grid and suggests placing the subject on a line or an intersection.
Shutter speed: How long the sensor is exposed to light, usually a fraction of a second. It decides whether movement is frozen or blurred.
Stop: A doubling or halving of light. Every exposure control is measured in stops, which is what lets them trade against each other.
Viewpoint: Where you stand and how high you hold the camera. The one compositional choice that changes the relationships between everything in the frame.
White balance: The camera's correction for the colour of the light, so that things which are white in life come out white in the photograph.
Zone system: A way of describing brightness in eleven steps, from pure black to paper white, each one stop apart.
Zoom lens: A lens covering a range of focal lengths. More flexible than a prime, usually with a narrower maximum aperture.