Disk Utility can ensure none of your footage goes awry
in transition to your Mac
Buy any video camera on the market today and the chances are
that it records to some sort of memory card. This may seem like an obvious
point, but just five years ago pretty much everything was tape-based.
In the old, when you used to record to tape, you’d leave the footage on them
as a backup
Recording to memory cards brings many advantages: there’s no
capturing, you don’t need to worry about chewed tapes and the media can be
instantly re-used. However, there’s one thing that you don’t get when recording
to memory cards a built in archive.
During the days of tape, while you could re-use the tapes
again, in practice you never did. The more times you ran a tape through a
camera, the more likely it was to get chewed. The cost of a new tape versus the
risk of losing footage simply wasn’t worth it. This meant that after you’d
captured the tape, you could archive the tape and you’d have a backup of the
footage sitting on the shelf if anything happened to the files.
If you were lucky enough to shoot on a hybrid camera that
could record to tape and memory card simultaneously, you had an instant backup
while you were recording. If anything went wrong with the card, you had the
tape copy to fall back on.
When you shoot to memory card, all your eggs are in one
basket until you’ve transferred the files to another hard drive. Some cameras
have dual slots, so can record a backup at the same time, which helps minimize
the risk, but you still need to wipe both cards eventually and re-use them.
Moving files from card to Mac may seem like a simple
procedure but if you get it wrong and lose some footage, it could be an
extremely expensive mistake. In the worse case scenario, you may have to re-do
an entire shoot, which is a considerable cost, or if it’s a live event, the
footage could be lost forever, no doubt like your client. Even if you think
you’ve copied everything over, it’s only when you come to the actual edit
(which could be days or even weeks later) that you’ll actually know. By then,
you’ve probably wiped the memory cards and re-used them.
And once the files are on your Mac, there’s the matter of
backing them up and archiving them. There are lots of programs out there to
help with the media management process, which include nifty features such as
the ability to verify that files have been copied correctly, but there’s a
utility included for free with every Mac that can also help considerably with
the process - Disk Utility.
Disk Utility is a tool for managing disks in your Mac. It’s
mostly used for formatting new disks, but it can do a lot more. For video
purposes, its most useful feature is the ability to create disk images. A disk
image is an exact copy of a computer disk, but written to a file. Load the disk
image, also known as mounting, and it will appear to computer as if the disk is
still attached. It’s an extremely useful trick.
Instead of copying the files from the memory card to a
folder on your Mac hard drive, you can use Disk Utility to create an image of
the memory card instead. This has a number of advantages. First, you’ll
preserve the exact file and folder structure of the memory card. These
additional files and folders sometimes contain metadata created by the camera
and if you only copy the folder containing the video files, you’ll lose them.
Stuff the archives, Disk Utility can create different types of disk image,
but the compressed read-only option is the best for archive purposes
If you create a unique name for each memory card before
creating the image, then when you mount the image it will appear the same to
any Mac on which you mount it. For example, format a card in a Canon camera
and it will show up in the left-hand Finder panel as EOS_DIGITAL. You can
right-click on this and rename it to something more useful - I use a three-
letter prefix to help make it unique, a number that used to correspond to the
tape number and finally which number CF card it is. So if I’m shooting on CF11
and the last tape number was 256, I’d rename this card FXT257CF11, the next
would be FXT258CF12 and so on.
To create the disk image, simply start Disk Utility, click
on the drive in the panel on left and click the new image button. To create an
archive, the default option - compressed - is the best to go for. This will
create a read-only image that’s as small as possible. As video files are
heavily compressed already, it won’t be able to compress them that much
further, but it will compress any empty space on the memory card. If you chose
just the read-only format, then a16GB card would create a 16GB image - even if
there was only 1GB of files on the card. You’re creating a bit for bit copy of
the memory card - including all the unused bits.
Devices squad, when you mount a disk image, it appears in the left-hand pane
of Devices in the Finder like a regular memory card in a card reader
The useful part is that because the card is called
FXT257CF11, when the image is mounted, it will also appear as that in the
left-hand panel in Finder. When you mount a drive - whether it’s a real drive
or a disk image - OS X adds it to a special directory called /Volumes on your
hard drive. So as far as Mac programs are concerned, the disk image always
appears at /Volumes/FXT257CF11. This will be the case whichever Mac on which
you mount the disk image, so it’s especially useful if you work across many
different machines. You no longer need to manually locate files when you
transfer a project from one machine to another-as long as you’ve mounted the
disk image before firing up your edit application, the video files will be
where it’s expecting to find them.
Know your place, as far as the file system is concerned, all disk images
appear in a special folder called /Volumes, which means your files will be in
the same place whichever Mac you use them on
As the disk image is read-only, applications can’t alter the
files without you knowing. Some editing programs try to add extra metadata to
files when you import them. Since this disk image is essentially your digital
negative, you don’t want editing applications messing around with the files.
When the disk image is created, Disk Utility also adds some
extra information so it can validate the data is correct and hasn’t been
corrupted. The first time you open the disk image, the Finder will verify the
image. This is a useful, if time consuming, check that lets you know that the
disk image is a perfect copy of the original. The verification process only has
to run once - next time, it will open much more quickly. If you’re in a rush,
you can skip the verification process and the Finder will attempt to run it
next time you mount the image.
Better than the real thing, Disk Utility creates a replica of the source
drive and saves it to a single file, called a disk image
When you consider how valuable your source files are, it’s
important to back up and archive them properly. Using disk images will help
with this process and also adds additional extra checks, such as verification,
to ensure that the files have been copied correctly. It does add an extra layer
to your workflow, but the advantages it brings in many cases outweigh the
extra steps involved.
All present and correct, when you create a disk image, or copy it to a new
drive, the Finder will verify that it’s a perfect copy the first time you open
it
