A modern CMOS image sensor (CIS) is not only a high-precision, high-dynamic-range, mix-signal electronic device, the system design also requires an integrated consideration on optical imaging function. As pixel size continues to scale down, pixel performance needs to be maintained at an equivalent level to avoid overall image quality degradation. This paper describes several system-level properties such as quantum efficiency, noise performance, and crosstalk under illumination of a tilted incident angle.