CMOS image sensors are integrated circuits, or chips, that work as digital equivalents of film in analog cameras: their function is to record the captured image. The name "CMOS" is an acronym for complementary metal-oxide semiconductor. An active-pixel sensor (that is, with one photodetector and an active amplifier for each of its millions of pixels), a CMOS sensor works by converting photons (light particles) into electrons, which enables the analog-to-digital image processing.
CMOS has increasingly replaced CCD image sensors. The advantages of CMOS sensors include faster data transmission and processing, considerably lower power consumption, cheaper production cost, and the ability to perform some digital processing tasks (such as noise reduction) directly on the CMOS chip. Although CCD sensors are less susceptible to image noise and generally more sensitive to light, the benefits offered by CMOS have turned it into an industry-favorite. Moreover, CMOS sensor technology has helped reduce digital camera prices, and continued research developments have improved the low-light performance of CMOS image sensors.
CMOS sensors have been used in digital photography since the 1990s; however, like digital photography itself, CMOS went through a gradual evolution until reaching its current status as the market's favorite image sensor technology.
For a long time after entering the mobile market, CMOS sensors were used only in flagship models. Today, however, this image sensor technology can be found in practically every mid-range and high-end phone.