Methods and apparatus are disclosed for locating an area of interest within a digital image of a form captured by an imaging scanner. Specific examples include methods and apparatus for optical mark reading with a digital imaging scanner. In many of the methods, an image of a response form is captured by a scanner, and target areas for possible responses are located within the image based upon an expected location being adjusted as necessary for certain error-inducing defects in the forms or scanning process. Also disclosed are steps to normalize the darkness values of pixels captured from an optically scanned form.