A method for determining defects in an image sensor, which identifies one or more partial column defects, including capturing a digital image using the image sensor and storing such digital image in a memory; identifying at least one column in the digital image which has corrupted data caused by one or more defective pixels in the image sensor; processing the digital image data from the at least one identified column using an extended differentiation filter; and using the output of the extended differentiation filter to identify a starting position or an ending position of the partial column defect.