The effects of time- and frequency-averaging during correlation (or later) act to smear out the response of a point source located away from the phase center of the correlation. For this review, we'll take the formulae from Wrobel (1995), §21.7.5. These provide the maximum field of view having no more than a decrease in the response to a point source. We recast these formulae in terms of correlation parameters that you can select. For more information about the derivation and behavior of time- and frequency- (also called bandwidth-) smearing, see Bridle & Schwab (1989). Further, image distortion due to the non-coplanarity of the observing array, which we don't dwell on here, is discussed in Perley (1989).