Apple Final Cut Express HD - Manual (Page 154)

154 Part III Setting Up Your Editing System
If your hard disk or its connection to your computer does not support the data rate of
your video format, you need to consider three factors:
 Sustained transfer speed is a measurement of how fast data can be written to a disk
in MB/sec.
 Seek time is a measurement of how quickly data stored on the disk can be accessed
in milliseconds (ms). Low seek times are important when playing back an edited
sequence of clips, because the disk must spend a lot of time searching for the next
clip to play.
 A faster spindle speed increases a disk’s sustained transfer rate (typical multimedia
disks run at 7200 revolutions per minute, or rpm). However, the faster a hard disk
runs the more it heats up, so ventilation is important when you install disks internally
or in external enclosures.
Note: Removable media drives such as Jaz, Zip, and CD-RW drives are not suitable for
video capture and playback because of their low data transfer rates.
Determining How Much Space You Need
The amount of disk space you need depends on the specifications of the video format
you are using for editing and how much source footage you have.
Know Your Shooting Ratio
Remember that when you start editing a movie, you need to capture much more
media than you will use in the final movie. The ratio between the amount of footage
you begin with and the final duration of the movie is called the shooting ratio. When
you are estimating how much disk space you need for a project, calculate it based on
the total amount of media you plan to capture and use during editing, not the
intended duration of the final movie.
Planning for Additional Media Files
In addition to space for captured files and project files, you need extra space for render
files, graphics, movie files created in other applications (such as animations), additional
audio files, and so on. A loose rule of thumb to determine how much space you need is
to multiply the amount of space needed for your finished program by five.
Ultimately, the amount of extra space you reserve depends on how much additional
media you create during editing. For example, if you use hardly any effects, additional
render files may not be a factor. If you are using only a few graphics files and little
additional audio, these may not be a concern, either.
Keep in mind that although real-time effects don’t require additional drive space for
rendering, you still need to render the effects at high quality for final output, so at that
point you need enough drive space for render files.