Aperture An opening behind the lens of a camera. Its size can be adjusted to control how much light enters the camera.

Camera A device that records an image of a scene electronically or on photographic film. The main features of a camera are a lens and a shutter. Light from a scene is let into the camera when the shutter opens. The lens focuses the light on to the back of the camera. In this way it makes a small copy of the scene called an image. The image is captured on a memory chip or on a strip of photographic film.

Camera phone A mobile phone or smartphone that is able to capture photographs and video. A phone's digital camera usually contains a fixed-focus lens, which is not adjustable.

Charge-coupled device (CCD) A device that divides an image into pixels, measures the brightness and colour of each one, and digitizes the readings.

Compact camera A "point and shoot" camera that is designed to be simple to use. Most compact cameras can set the focus and exposure automatically, and have a built-in flash.

Daguerre, Louis (1787–1851) French chemist who developed the daguerreotype, an image fixed on a copper plate using salt.

Dark room A room where photographs are developed. Dark rooms are often lit by red light, because most photographic paper is sensitive only to blue and green light.

Developing process The process by which photographic film and paper is treated to create a fixed image. It is first soaked in chemicals called developer, which reveal the images. Then it is soaked in a stop bath to halt the developer, and washed in water.

Digital camera A camera that stores images on a memory chip or a disc.

Digital single-lens reflex camera (DSLR) A digital camera that combines the workings of a single-lens reflex camera with, instead of film, a digital "back": a charge-coupled device (CCD) to capture the image.

Eastman, George (1854–1932) American inventor who developed flexible, photographic film. Films could easily be sent away for developing, which helped to make photography a popular hobby.

Enlarger A device used to make photographic prints. It projects light through a negative on to photographic paper. The projected image can be focused and its brightness altered.

Exposure The amount of light that reaches the film or CCD in a camera. It can be controlled by adjusting shutter speed or aperture size. Exposure must be just right or the image will be too bright or too dark.

Flash A device on a camera that produces a brief flash of light to illuminate a scene.

Focus The clarity of an image, controlled by the position of the lens, which directs light rays on to the CCD or film.

Fox Talbot, William (1800–1877) English inventor who developed the negative-positive process in photography.

Lens A shaped piece of glass or plastic that bends light rays. Cameras use a convex (bulging) lens to focus light.

Light meter A device that measures light levels to calculate the right exposure.

Megapixels One million pixels. Megapixels are used to measure the resolution of a digital camera.

Memory card An electronic data storage device that can be erased and re-recorded. A memory card is also sometimes known as a flash card.

Negative An image where light and dark tones are inverted. In colour negatives, the colours are reversed into their respective complementary colours (e.g. blue to yellow).

Negative-positive process The process in which a negative is used to print a positive image. Lighter areas in negative film allow more light through them than dark areas do. The photographic paper beneath these areas is therefore exposed to more light, so will turn dark when developed.

Niépce, Nicéphore (1776–1833) French inventor who took the first photograph in 1825 and the earliest surviving photograph in 1827.

Photographic film A strip of plastic coated with light-sensitive chemicals. When light from a scene is focused on the film, chemicals in bright parts of the image change, forming a pattern. This becomes visible when the film is developed. Colour film contains three layers of chemicals to record red, green and blue light.

Photographic paper Paper coated with chemicals that change when exposed to light. The changes become visible when the paper is developed.

Pixel The smallest part (usually a dot or square) of a digital image when it is represented on screen. Pixel is short for "picture element". Each pixel is a sample of the original image. The greater the number of pixels, the greater the resolution—and the more accurate the image.

Shutter A device that opens and closes to control the length of exposure.

Single-lens reflex camera (SLR) A camera that uses a mirror to reflect light from its lens to the viewfinder, so the photographer can see exactly what the image on the film will be. When the shutter-release is pressed, the mirror flips out of the way.

Viewfinder The lens that a photographer looks through to compose a photograph.

Zoom A device that can enlarge or minimize an image. Optical zooms use a lens that moves forwards or backwards. Digital zooms electronically crop or enlarge an image, resulting in lower resolution.

Consultant: Chris Oxlade