Sensor size

This is the physical size of the sensor, which is independent of the number of megapixels it has. Bigger sensors capture more light and produce sharper, clearer images with less noise. In fact sensor size is the single most important factor these days in a camera’s picture quality – megapixels are mostly secondary.

Sensor basics

There are two main things to look for in sensors: the sensor size and the resolution, in megapixels. It’s more important to get a bigger sensor than to get more megapixels.

Resolution

This can mean one of several things depending on the context. Camera resolution is the number of megapixels on the sensor, lens resolution is how well the lens is able to resolve fine detail. Screen resolution is the number of dots on the screen and therefore how sharp/clear it looks.

Photosite

This is the correct technical name for the individual light receptors on a sensor, though many people call them pixels because each photosite corresponds to a pixel in the final image. Each photoreceptor gathers light (photons) and turns them into an electrical charge (electrons) which can be measured.

Pixel

The individual building block of digital images. Each individual pixel is a single block of colour, but when there are enough of them viewed from far enough away they merge to form the impression of a continuous-tone photographic image.

Microlens (sensor)

In order to maximise their light gathering power, each photosite on the camera sensor is covered by a tiny domed ‘microlens’ to capture and funnel in the light more effectively. Improvements to the microlens array can improve the sensor’s performance.

Megapixels (MP)

The number of pixels captured by the camera’s sensor. Smartphones typically have around 8 megapixels and upwards, while regular digital cameras typically have 16 megapixels or more. Megapixels used to be a good guide to image quality but now sensor size is more important.

Full frame sensor

This is a sensor the same size as the 35mm film negative, measuring 36 x 24mm. This is the most desirable camera type for most enthusiasts and pros, but full frame cameras are bigger, heavier and more expensive. Most DSLRs and mirrorless cameras use smaller APS-C sensors.

Foveon sensor

Sigma’s Foveon sensor uses a unique layered design to capture blue, green and red light on separate layers. It mimics the multi-layer construction of colour film.

EXR sensor (Fujifilm)

A type of sensor used by Fuji in its smaller compact cameras with special modes for increased sensitivity or increased dynamic range. Confusingly, ‘EXR’ is also the brand name given to the image processing system used across the Fuji camera range.