Abstract: Performance metrics for an imaging system are assessed in the field, without the need for carefully-controlled conditions, such as lighting. In some embodiments, a hand-held test target is used to measure MTF, and to identify any undesired noise-reduction operation applied by an image signal processor. A metric-based heuristic enables prediction of whether an imaging system will be suitable to detect and decode a digital watermark signal of a particular resolution. A variety of other features and arrangements are also detailed.