The membership function for implementing the enhancement algorithm as described by Pal and King (1981, 1983) is modified here. The modified version enables one to avoid using contrast intensification (INT) operators for enhancement and has been found significantly to reduce the time of computing the algorithm in addition to providing a better approximation to the standardSand Π membership functions. To give a quantitative evaluation of their relative performances, an edge ambiguity index has also been defined through fuzzy measures in a set. The value of the index is maximum for image input and decreases as the ambiguity in detecting edges diminishes. The δ(X) value, as expected, is also found to increase with increasing standard deviation of the noise injected onX.