This paper analyzes the components of the spatial frenquences in a speckle shearing photography. The result has shown that the speckle construction in dark fringe areas is equivalent to the incoherent superposition of two speckle image field produced by each semi circular lens. It is somewhat different from that obtained by Y. Y. Hung. Using two concepts, which are the directional aperture of recording pupil and the boundary of diffraction halo of spatial spectrum by Fourier transformation from specklegram, two equations corresponding to the areas of light. and dark fringes have been deduced. Experimental results for demonstration, are provided, and the optimum figure of bandpass spatial filter is proposed. The results not only can be used to improve the quality of fringe pattern by image-seaving camera, but also may be useful for the study of electronic speckle searing interferometer.