1. A method for compensating trembling of a portable terminal, the method comprising: obtaining first and second images having different brightness by closing an iris within different intervals; computing motion vectors at respective regions of the first and second images and generating search matrices of the respective regions; searching locations having a similar saturation in the search matrices of the first and second images; and compensating saturation or brightness of the first image, wherein searching locations having a similar saturation comprises: computing saturation and brightness of each pixel of the first and second images; determining saturation of a pixel existing within the search matrix of the first image; and searching for a pixel having a saturation similar to the determined saturation within the search matrix of the second image, which corresponds to the search matrix of the first image.