A method for checking a prescribed optical security feature on a prescribed portion of a value document based on pixel data of pixels of an image of the portion which are associated with places on the portion and render optical properties of the value document at the places. A check is made of whether a first number of those pixels whose pixel data, according to a first prescribed criterion, lie within a first reference region prescribed for the security feature exceeds a first minimum hit value prescribed for the security feature, and whether a first scatter of the pixel data of the pixels exceeds a first minimum scatter value prescribed for the security feature. An authenticity signal is formed which represents an indication of authenticity only when the first number exceeds the first minimum hit value, and the scatter the first minimum scatter value.