A method of operating an image-based self-service check depositing terminal comprises receiving from a customer a check to be deposited, capturing image data which is representative of a first check image, binarizing the captured image data to provide a second check image which is a binary form of the first image, determining a check image quality value associated with the second image, comparing the quality value with a first threshold, transmitting the second image to a back office facility when the quality value is outside of the first threshold, comparing the quality value with a second threshold which is different from the first threshold, returning the check to the customer when the quality value is outside of the second threshold, and transmitting the first image to a back office facility when the quality value is between the first and second thresholds.