A demagnifying image intensifier is proposed using parallel converging electric and magnetic fields. The design of such a tube is considered and the results of calculations for the particular case of conical fields are presented; the diameter of a typical disk of confusion for a linear demagnification of 5:1 and minimum flux density of 10−2weber/m2is found to be <0.004 cm. Suggestions are made for a tube incorporating an intermediate stage of electron multiplication.