Under dark illumination, a photographer is usually faced with a frustrating dilemma: to use the flash or not. A picture relying on the available light usually has a warm atmosphere, but suffers from noise and blur. On the other hand, flash photography cause unacceptable artifact such as flat and harsh lighting, although it provides more details. Some researchers proposed the detail transfer approach to enhance the flash photography by combining a picture taken with the available light and one taken with the flash. However, they do not focus on the problem of image registration. Image registration is important for images taken with handheld cameras, for example, changing the camera settings often results in camera motions. Since the flash/no-flash images do have significant differences due to the change in illumination, in this paper, a robust image registration method based on FFT is proposed for registration of such image pairs. An image pair with moving objects is used in this paper to demonstrate the robustness of the proposed method. We also figure out the problem of the conventional methods of flash photography enhancement, a large amount of memories are required during the computation. It can be a serious computational burden when the size of the input images is large. In this paper, we propose a new method based on YSbSr color space to alleviate this problem. Experimental results show that the advantages of the proposed method include: (1) It saves up to 50% of the memory space; and (2) It preserves more details and sharpness than the approach based on YC bCr color space when the same quantity of memory is used.