The reason is simple, when you do wildlife you get 80 to 90% garbage, you can´t keep that garbage in HDD without making a big confusion and occupying large portions of the discs that are useless. On the other hand there are many situations on which you frame, iluminate, set parameters and pull the trigger of the FS-4HD and when you come back 3 or 4 hours later you might get a few seconds of a hummingbird that made your day, normally a couple of minutes in the middle of 3 hours footage. It has to be cleaned up.