Most of images like medical images, satellite images and even real life photographs may suffer from poor contrast due to the inadequate or insufficient lighting during image acquiring. So there is a necessity of contrast enhancement of images. In this paper three enhancement techniques namely fuzzy rule based contrast enhancement, contrast enhancement using intensification (INT) operator, and contrast enhancement using fuzzy expected value (FEV) are presented for the low contrast grayscale images. Comparative analysis of these enhancement techniques is carried out by means of index of fuzziness (IOF) and processing time.