1. A method for examining the optical condition of a value document on the basis of a digital image of at least a specified region of the value document, the digital image comprising pixels, said method comprising the steps: searching pixels of the digital image for sets of error pixels, wherein the error pixels fulfill a specified deviation criterion for an impermissible deviation of at least one specified pixel property in order to determine pixels that lie outside a reference distribution for permissible pixel properties, and a distance of each error pixel of the respective set from at least one other error pixel of the same set is smaller or equal to a specified distance that is greater than the distance of directly neighboring pixels of the digital image, and ascertaining a number of sets found during the search and/or a value for at least one property of at least one of the sets found during the search.