A 10T/pixel CMOS active pixel sensor with clock count output, ultra low supply voltage, and wide dynamic range is presented. This pixel comprises a reset transistor, photo-diode, a comparator, and an inverter with pixel size of 9.4x9.4μm2 and 24% fill factor in a standard 0.25-μm CMOS logic technology. The output transfer curve is the same as an amplified logarithmic-response and is similar to the light response of the human eye. Besides, the pixel can operate at an ultra low supply voltage and the output characteristics will not be affected. Even with supply voltage down to 1.2V, the dynamic range of this pixel can remain as high as 90dB.