A model for prediction of minimum resolvable contrast (MRC) as applied to TV sensors, and an MRC measuring instrument, have been developed. Several equations exist for calculation of MRC, deriving from the work of Rosell on vidicon based sensors, and these form the basis of our model. Recent workers touch on the MTF of CCD sensors, and such work, together with a derivation of noise equivalent contrast, has been applied to extend the applicability of our model to these types of sensor. A means of directly evaluating the MRC concept was also desired, both to validate the model, and to measure the performance of individual sensors. A compact MRC measuring instrument was therefore built, and details of its construction and use are presented.