In digital devices, the image is captured by an electronic image sensor. The lens projects the image onto the sensor, which converts the image into an electrical signal. The image sensor, or sensor, consists of individual pixels, and these pixels correspond to the pixels in the resulting photograph. The resolution of the sensor can be understood similarly to digital images. One megapixel represents one million pixels. Prints made from a 10x15 cm digital photograph typically require around 1 megapixel. For DIN-A4 format prints, it is advisable to have a resolution of at least 3.5 megapixels.

Among image sensors, we distinguish two main groups: CCD (charge-coupled device) and CMOS (complementary metal-oxide-semiconductor). They primarily differ in their manufacturing processes. CCD sensors are more commonly used, as they offer higher sensitivity, but they consume more power. CMOS sensors are less frequently installed in devices, but they have advantages such as lower cost, lower power consumption, and lower thermal noise due to reduced heat generation, resulting in better image quality.