1. A method for generating a focus signal, comprising: capturing an image that has a plurality of edges each having an edge width, the image being captured using a first pixel array; providing an exclusion filter that performs a discrimination between a first edge and a second edge based on at least a characteristic of the first and second edges, the characteristic not being related to a location of the first or second edge, the exclusion filter using an exclusion range created from a histogram of the characteristic for edges in a prior image captured by the first pixel array; and, generating a focus signal that is a function of the edge width and the discrimination.