The central electronic component of a digital camera or camcorder is the image sensor. Together with the lens and the image processor, the image sensor is a deciding factor of the picture quality of a digital camera. The image sensor takes the place of a film negative of an analogue camera and consists of many millions of light-sensitive photodiodes that convert captured light photons into electrical signals. These photocells are arranged in matrix-like columns and rows on the area sensor. The image sensor then accumulates the individual image points as an electrical image, which is known as a pixel. The number of pixels a sensor can accumulate produces the picture’s resolution.
The choice of the sensor size depends mostly on your available budget as well as your personal requirements for picture quality and the quality of the motif you would like to photograph. The bigger the sensor is, the higher the luminosity and the more image information it is able to record. Larger sensors are thus capable of producing a high picture quality, but are at the same token expensive and require the use of a high-quality lens, which also does not come cheap. Also, the sensor has a considerable effect on the overall weight of the camera, which should be considered, for example, when traveling.
For compact cameras, mostly smaller image sensors are used, which are from 4.5 x 3.5 mm to 5.4 x 4 mm. Nowadays, camera manufacturers mostly use CMOS technology for these requirements. Most of the time, image sensors in interchangeable lens cameras, such as those offered by Olympus and Panasonic, are notably larger and support the use of market-dominant Four Thirds sensors starting from 17.3 x 13 mm. Canon, Samsung, and Sony, on the other hand, use the APS-C sensor, which is a bit bigger at 22.2 x 14.8 mm. Nikon is an exception and uses two non-standard formats: the CX format sensor, which measures 13.2 x 8.8 mm, and the DX format sensor, which measures 24 x 16 mm. The largest image sensor is the medium format, which measures 48 x 36 mm. Full frame sensors, coming in at 36 x 24 mm, are a bit smaller. Nikon refers to this format as FX format.
Along with the size of the sensor itself, the number and size of the photocells also play a role. These three parameters, along with the image noise and the photosensitivity, determine the image resolution and are therefore crucial for the quality of your pictures.
As a measurement of the image resolution, the number of pixels is given in megapixels (MP) and depends on the size of the image sensor and size of the pixels. Be careful not to mix up the actual number of pixels the camera can depict with the number of photocells. The bigger the pixel depicted is, the lower the image resolution will be. The number of pixels in image sensors is between 0.3 and 10 MP while professional digital cameras are capable of depicting tens of megapixels.
The sensor sensitivity is yet another parameter of image sensors. This is measured in ISO values. The bigger the image sensor is, the higher its light sensitivity, which decreases with a higher number of pixels. Between 50 and 200 ISO is the basic sensitivity of image sensors. This setting can be raised when needed in order to alter the exposure of the photocells.