This invention provides a display system that receives an image signal containing a binary data of N bits, wherein N is a positive integer, for displaying an image with a grayscale corresponding to the binary data. The display system further includes a data converter for converting M-bit of the N bits of the binary data into a non-binary data, wherein M is a positive integer and N≧M, for applying the non-binary data as a sub-frame in controlling the gray scale in displaying the image. In an exemplary embodiment, the data converter converts consecutive M-bit of the N bits of the binary data into the non-binary data. The display system further includes a spatial light modulator (SLM) having a plurality of pixel elements and the SLM receiving the non-binary data of M bits for controlling the pixel elements.