Final answer:
In cameras, the lens is typically adjusted relative to the detector to focus the image, with smartphones doing it electronically and DSLRs mechanically. The CCD detects light via photons that produce electrons, forming an electronic image.
Step-by-step explanation:
In order to focus the image on the detector, such as film or a CCD (charge-coupled device), in a camera, the lens is typically moved relative to the detector. For instance, in a smartphone camera, which has a fixed lens and CCD, focusing is achieved electronically. The lens system or some part of it is adjusted so that the optical path appropriately focuses light on the CCD. In professional or DSLR cameras, this process is mechanical, where the lens physically moves either manually or through autofocus systems according to the required focus distance to ensure the sharpness of the image. Photons hitting the CCD's pixels generate electrons that are stored, creating an electronic image that digital imaging systems can process. This is a critical function of cameras used in a wide variety of fields, from personal smartphones to astronomical research and biomedical imaging systems.