Camera
Sensor Size
The physical dimensions of a camera's image sensor. Larger sensors capture more light per pixel at the same aperture, producing better noise performance and allowing more background blur. Micro Four Thirds uses a 17.3 x 13mm sensor.
Sensor size refers to the physical dimensions of the light-gathering surface inside a camera. Common sensor sizes in interchangeable-lens cameras range from Micro Four Thirds (17.3 x 13mm) through APS-C (approximately 23.5 x 15.6mm for most brands) to full-frame (36 x 24mm). Medium format sensors are larger still. The dimensions determine how much of the light projected by the lens falls onto the sensor and how large each individual pixel can be at a given resolution.
A larger sensor at the same pixel count has larger individual pixels. Larger pixels collect more photons per unit of exposure time, which improves signal-to-noise ratio and results in less visible noise at high ISO settings. Full-frame sensors at equivalent megapixel counts therefore tend to produce less noisy images in low light than APS-C or M43 sensors at the same ISO. However, sensor generation and design matter as much as physical size — a modern BSI stacked M43 sensor may outperform an older full-frame sensor in practical low-light tests.
Sensor size also determines the crop factor applied to lenses. A Micro Four Thirds sensor has a crop factor of 2x relative to full frame. A 25mm lens on M43 gives the same angle of view as a 50mm lens on full frame. This crop factor has a direct consequence for depth of field: achieving equivalent background blur to a full-frame camera requires an aperture two stops wider on M43. A 50mm f/1.8 full-frame combination is visually equivalent to a 25mm f/0.9 on M43. For telephoto photography, the crop factor is an advantage — a 300mm f/4 lens gives 600mm full-frame equivalent reach on M43 in a far smaller and lighter package.