An example embodiment may involve capturing a sequence of images, wherein there are 4 or more images in the sequence of images, and wherein each of the sequence of images has an exposure length of 4-100 seconds; applying a sliding window over the sequence of images as downsampled, wherein at least 4 images are encompassed within the sliding window’, and wherein for each position of the sliding window the applying involves: (i) aligning a set of images within the sliding window, and (ii) merging the set of images as aligned into a video frame; combining video frames generated by way of the sliding window into a video file; and storing, by the mobile device, the video file in memory of the mobile device.