1. A method for adjusting an image shown on a display apparatus adapted for a display wall, the display wall comprising a plurality of display apparatuses, each of the display apparatuses having a scaler and a digital display element, the method comprising the steps of: the display apparatuses receiving a video signal; setting an initial image capture area in the scaler for selecting and scaling a part of a video image and transmitting the part to the digital display element for display; and choosing one display apparatus of the display wall to adjust the image until all of the display apparatuses are adjusted, wherein: a. when the initial image capture area is adjusted, one side of the initial image capture area is fixed and a size of the initial image capture area is adjusted to form a size of the adjusted image capture area by adjusting another side of the initial image capture area; and b. updating a scaling factor of the scaler according to the size of the adjusted image capture area so that the image of the adjusted image capture area fits an output display area of the digital display element of the display apparatus.