The shortcomings of conventional scintillation cameras are analysed theoretically with a view towards improving performance at gamma ray energies above 140 keV. A camera design is proposed which incorporates several new features to obtain good spatial resolution from thicker crystals of sodium iodide. Computer simulations show that in addition to having good efficiency and spatial resolution, the new design allows parallax error correction and (possibly) Compton scattering correction at gamma energies up to 511 keV.