A new technique for recording the shadow image of a moving projectile is presented. The technique is both simple to understand as well as efficient in image recording and processing. The key to the method is the way in which the photoswitch array produces two analog output corresponding to the positions of the upper edge and the lower edge of the projectile. The two outputs are converted into a digital data stream and acquired by a computer. A simple computation is applied to reconstruct the image. Analytical results for system transfer function and time response is evaluated and verified experimentally.