We have investigated the thermal emission of midinfrared dielectric photonic crystals. We show that the optical properties of the photonic crystals can be probed by the photomodulation of the room-temperature thermal emission. The technique is illustrated in the case of membrane-type two-dimensional photonic crystals. The GaAs-based photonic crystal membranes were fabricated by wafer bonding followed by standard e-beam lithography and etching processes. Thermal radiation collected from the surface of the sample allows one to investigate experimentally a broad spectral range from 500 to 1500 cm −1 . Zone-center modes at the point coupled to the radiative continuum are evidenced around 900 cm −1 11 m wavelength. The lattice period-icity of the photonic crystals allows one to spectrally tailor the emissivity. Three-dimensional finite-difference time-domain modeling is used to explain the thermal radiation spectra of the photonic crystal characterized by optical sources embedded in the whole structure.