A new automatic exposure system for digital still cameras

This paper presents a newly developed automatic exposure (AE) system for digital still cameras (DSC). The through the lens (TTL) system which has been employed mainly by conventional camcorders has been applied as an exposure control system for DSCs. However, the TTL system requires a longer time to obtain an appropriate exposure value, and it is therefore not a suitable control method for DSCs which demand immediate imaging after the shutter button is pushed. The authors have developed a high-precision AE capable of controlling the exposure quickly by converting the brightness of an object directly using the obtained value of an integrated image without using the photometric sensors other than a charge coupled device (CCD). They have also confirmed that the new system enables excellent exposure control without any problem.