We propose and analyze a generalized model of photodetection in which the detector couples simultaneously to both electric and magnetic components of the electromagnetic field. Extending Glauber's seminal theory, we show that such detectors, now experimentally feasible via meta-materials, can yield interference patterns that depend strongly on the internal response of the detector. In particular, we show that for a two-source interference setup, coherent electric-magnetic dipole coupling can suppress or enhance interference visibility, revealing a clear instance of measurement contextuality in quantum optics, where the outcome depends on how the system is probed.