Retarding field analyzers of the plane parallel plate, the spherical condenser, the Faraday cage, and the filter lens types are examined in some detail. The often neglected lens effect of the hole in the plane parallel plate through which the beam passes is shown to have significant effect on the energy resolution. The previous analysis of the spherical condenser is extended to the hemispherical case and the effect of the aperture in the inner sphere calculated. It is shown that for certain relations between the sphere sizes and the position of the source very high resolution may be obtained. The general restrictions on the performance of imaging retarding fields are considered and a design procedure based upon empirical knowledge of immersion lenses is given.