Mengetahui berapa banyak foton yang jatuh ke permukaan fotoreaktif akan membebaskan elektron adalah ukuran akurat sensitivitas CCD. Hal ini disebut dengan [[efisiensi kuantum]] dan dinyatakan dalam persentase.
CCDs containing grids of [[pixel]]s are used in [[digital camera]]s, [[image scanner|optical scanners]] and video cameras as light-sensing devices. They commonly respond to 70% of the [[Incident ray|incident light]] (meaning a quantum efficiency of about 70%, ) making them more efficient than photographic film, which captures only about 2% of the incident light . As a result CCDs were rapidly adopted by astronomers.
An image is projected by a [[Lens (optics)|lens]] on the capacitor array, causing each capacitor to accumulate an electric charge proportional to the [[light]] intensity at that location. A one-dimensional array, used in line-scan cameras, captures a single slice of the image, while a two-dimensional array, used in video and still cameras, captures the whole image or a rectangular portion of it. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbour. The last capacitor in the array dumps its charge into an [[amplifier]] that converts the charge into a [[voltage]]. By repeating this process, the control circuit converts the entire contents of the array to a varying voltage, which it samples, digitises and stores in memory. Stored images can be transferred to a printer, storage device or video display. CCDs are also widely used as sensors for astronomical [[telescope]]s, and night vision devices.
An interesting astronomical application is to use a CCD to make a fixed telescope behave like a tracking telescope and follow the motion of the sky. The charges in the CCD are transferred and read in a direction parallel to the motion of the sky, and at the same speed. In this way, the telescope can image a larger region of the sky than its normal field of view.
CCDs are typically sensitive to [[infrared]] light, which allows [[infrared photography]], [[night-vision]] devices, and zero [[lux]] (or near zero lux) video-recording/photography. Because of their sensitivity to infrared, CCDs used in astronomy are usually cooled to liquid nitrogen temperatures, because infrared [[black body radiation]] is emitted from room-temperature sources. One other consequence of their sensitivity to infrared is that infrared from [[remote control]]s will often appear on CCD-based digital cameras or camcorders, if they don't have infrared filters. Cooling also reduces the array's dark [[current (electricity)|current]], improving the sensitivity of the CCD to low light intensities, even for ultraviolet and visible wavelengths.
Thermal noise, dark current, and cosmic [[ray]]s may alter the pixels in the CCD array. To counter such effects, astronomers take an exposure with the CCD shutter closed. This "dark frame" image is then subtracted from the original image to remove the thermal noise effects.