A handheld wireless communication device includes features that make it easier to differentiate among various keys and to correctly select a desired key. To counteract geometric distortion, a watermark reading process translates the data before extracting the digital watermark. Provision of a thin P-doped layer 52 on the illuminated rear surface provides both a diffusion barrier resulting in improved resolution and a functional shield for reference pixels. The present application also provides methods for computing a numeric metric of the aggregate opinion about some topic expressed in a set of expressions.