April 2011 |
Basics The technique of slow-motion movies could not be simpler: record a scene using a high frames per second (fps) setting then replay it at standard fps. This, of course, is much easier said than done. Fortunately, many modern digital cameras and videos have the capability built-in. Inevitably, there is a cost, the faster the recording speed the poorer the recording resolution. Here I will explain how I have created some useful results with some very modest equipment. First, the camera. I use a mid-range Fuji super zoom, capable of shooting at up to 1000fps. This may sound impressive but nothing is ever that easy, as I shall explain. My camera produces MOV files which my favourite video editor, Virtualdub, cannot read. It is supposed to be able to with a plug-in and Quicktime installed but I have had no joy making it do so. Instead, I convert the MOV to an uncompressed AVI and work from that. There are several free or low cost video format converters available. Probably the most flexible free converter is FFMPEG. This is something of a Swiss Army Knife for video, having many conversion options but this flexibility comes at a price. It is command-line driven using a multitude of cryptic commands and options. This is further exacerbated by minimal help documentation. Fortunately, others with a deal more time and patience than I, have created FFE (FFMPEG Front End). This provides a user-friendly graphical interface that creates the required commands and options then fires them at FFMPEG. Back to the camera briefly. Here is a table of its available speeds and resolutions:
As you can see, the resolutions at the higher speeds are very poor and would only be used if nothing else will do the job. I normally use 60fps, 120fps and, very infrequently, 240fps. Converting the camera's MOV to an uncompressed AVI in FFE is straightforward. I choose the "Uncompressed" codec as further editing in Virtualdub is almost certain. The kind of editing required is cutting the beginning and ends. Another consequence of higher speed recording is underexposed image. This can be compensated for to an extent, with the Levels filter. This behaves very like the Levels controls in an image editor. A histogram of recorded luminance levels is displayed and that range can be expanded to cover all the available range by simple controls, giving better image contrast and perceived brightness. |