One very useful feature of digital video cameras is the ability to control frame rates. For surveillance cameras, this can be very useful, as a lot of memory space could be saved by using low frame rates. This means that more footage could be stored for longer periods of time. This feature quite useful nowadays, as it could be hard to tell when footage will be useful for a particular purpose. This is especially true when the footage may be of use in a criminal investigation. This has become less useful however, given that computer memory space is now quite cheap and not much of an issue.