The image processing technology has played an important part in the history of digital still cameras. The technology which is used in cameras has realized wider dinamic range, lower noise, etc. That has provided camera users with the benefit of higher picture-quality and more successful shooting. Also in the phase of camera design, the image processing technology which simulates undeveloped cameras has indicated the expected picture-quality and has contributed to decision of camera specifications. This report introduces these image processing technology which realizes the present high picture-quality of digital still cameras.