Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for obtaining, in real-time from an image capture device, a video stream comprising images of a document by a computing device. The computing device provides, for display in an image preview window, the video stream overlaid with a graphical capture guide. In response to detecting a lighting artifact in at least one image of the video stream, the computing device modifies the graphical capture guide within the image preview window. The computing device captures one or more of the images of the document from the video stream.