The microchannel plates, on which are based the operation of two-dimensional photon-counting detectors, have a local dead time (at each microchannel) much greater than the frame time used to capture images in techniques of Speckle interferometry. This phenomenon restricts the conditions for use of these detectors with regard to luminous intensity and pixel size which must be kept within certain limits so that the detector works linearly and does not reduce the spatial resolution because of loss of coincident events. Models of these conditions are being analized to determine theoretically, and in laboratory tests, the conditions that determine the use of a given detector.