The factors impacting strain precision in the digital image correlation (DIC) method is derived theoretically. It is pointed out that the precision of strain calculation will decrease as the calculation window gets small. In order to improve the effective image resolution, a novel perspective to two-dimensional multi-camera full-field DIC method is proposed for slender specimen. The sub-pixel position of matching feature point pairs is found based on feature point detection and matching algorithm. The matching feature point pairs are registered with high precision using the DIC method. Finally, a gradually optimized homography solution method is developed to solve the image transformation to get the seamless stitched images before and after deformation. Two sets of experiments including pure translation and three-point bending of rubber beam are conducted. In the pure translation experiments, the mean error and root-mean-square error of calculated strain are within 50 με, which verifies the validity of this method. Two-dimensional and three-dimensional multi-camera DIC methods are compared through the three-point bending experiments. Based on the results, merits and demerits of the proposed method are discussed.