BOOT CAMP 192 (13/09/01)
MEMORY CARDS, part 2
Last week we looked at the four commonest types of memory
card used in digital cameras and other portable devices, like MP3 players,
camcorders and portable computers. To recap they are, in no particular order,
Compact Flash (CF) MultiMedia Card/Secure Digital Card (MMC/SD), Memory Stick
and SmartMedia. This week we'll be looking at the care and use of memory cards
and picture file handling.
Needless to say the four card types are physically and
electrically incompatible with one another and there are some differences in the
way they manage data and handle copyright material but apart from that the basic
attributes and the ways in which they are used are remarkably similar.
Most cards and sticks are based on NAND 'non volatile' or
'Flash' memory chips (NAND or 'Not-And' is a type of logic gate or switch used
in this kind of memory microchip), and it is extremely robust, both physically
and electrically. For example most types of card will operate happily in a wide
range of temperatures (-10 to +70 degrees C) and endure shocks of up to 200g,
which would destroy most other forms of data storage like disc drives (and
wouldn't do us humans much good either…).
Life expectancy is excellent, typically 500,000 to 1,000,000
hours MTBF (mean time between failure). Obviously that's a somewhat speculative
estimate and it's possible that the contacts on heavily used cards could fail
long before that but the bottom line is that most cards will outlive the devices
they're used with by a considerable margin. Most cards will withstand at least
1,000,000 read-write cycles but there's some speculation about how long the data
on a card will last before it irretrievably degrades. Manufacturer's estimates
vary from 5 to 25 years but since memory cards are not intended for long-term
storage or archiving it is largely academic.
Although memory cards are fairly rugged they should still be
handled with care and not exposed to excessive temperature, humidity vibration
and shock, at least any conditions that you wouldn't be comfortable in. Avoid
inserting and removing cards any more than you have to and when not in use they
should be carried in their storage cases or holders. Never touch the contacts;
in addition to the potential of damage from static electric discharge, the oils
and sweat on your fingers can damage the contacts or make them unreliable.
According to most expert sources the data stored on cards and sticks is not
affected by exposure low levels of electromagnetic and X-Ray radiation and cards
should be safe going through airport security scanners but if you're at all
worried you could put them in a 'film safe' container, keep them in your pocket
or allow them to be hand checked, rather than leave them in luggage.
Virtually all digital cameras come with a data transfer lead
that connects the camera to a PC so that images can be downloaded onto the PC's
hard drive. The lead connects to the PC's serial, parallel or USB ports and
works in conjunction with photo editing and filing software. Personally I avoid
cable connections like the plague. I've wasted many hours trying to get them to
work; the software is often flaky or fussy about what it shares a hard disc with
and occasionally both. Even when they do work they can be excruciatingly slow.
I've now given up and only use card readers and adaptors.
Readers plug into the PC's USB port and they are available for all types of
cards; universal or multi-format readers that can read two or three different
types are starting to appear. You can also get floppy disc adaptors for all card
types and PC-Card adaptors for SmartMedia and Compact Flash.
Windows treats a memory card in a reader or adaptor as a disc
drive, so you can move files to and from the card using normal drag and drop or
copy and paste techniques. Files on disc adaptors are treated just like standard
floppies. In addition to being simple to use readers and adaptors tend to be
much quicker than cable connections.
Since most digital cameras record images as standard JPEG or
TIFF files there is no need for specialist software, image files can be opened
and viewed using any paint or photo-editing program. The software bundles that
come with cameras usually include a 'photo album' program, to help you organise
your pictures. I've given up on those too; most of them are far too complicated,
simplistic or cutesy. All of the digital still camera image files on my PC
reside in a folder called 'Pix'; this contains a set of sub folders, one for
each event or occasion, with simple titles like 'Cornwall99' or 'Florida01'. I
generally copy files from the card to a PC as soon as possible, sometimes on the
spot if I happen to have a laptop with me as this provides a backup, in case
something unfortunate should happen to the card or camera.
I try to use up the space on the card and only erase the data
when it is full up and I always carry at least one spare. I recommend that you
get at least one, and make it a big 'un, the cards supplied with most cameras
are pitifully small usually only around 8 or 16Mb. Splash out on a 32, 64 or
128Mb card and you won't have to worry about running out of room, or wasting
camera battery power erasing files to make space.
To preview the files in a folder I use the thumbnail viewer
facility in Windows Explorer and the very excellent shareware utility ACDsee (http://www.acdsystems.com/index.htm)
or the picture-editing program that I happen to be using. Incidentally ACDsee
also has a useful slide view facility.
Finally, if you haven't already got one get a CD writer, this
will let you make regular backups of all of your photo files on CD-R discs.
These days' blank discs only cost a few pence and they should be good for at
least 25 years.
Next week – Electrical safety
Joint Photographic Experts Group. 'Lossy' picture file format
that uses data compression to reduce the amount of data, without unduly
Motion Picture Experts Group audio layer 3 -- digital audio
compression system commonly used to send files containing audio and music over
Universal Serial Bus, high-speed data connection system for
peripherals including digital cameras, modems, joysticks printers etc.,
Whether you're going out for lunch or just popping out for a
few minutes your PC is vulnerable to intrusion. Of course you could switch it
off and there are plenty of programs that will password protect your PC and
prevent Windows from loading, of you could invoke password protection on a
screensaver but all that takes time or they can be easily hacked. Quick Hide is
a useful little freeware program that locks the PC when it is running with a
simple keyboard shortcut. It can also be set to hide the current application,
the Taskbar and desktop icons, which can only be unlocked with a password. The
download zip file is under 500kb in size and it's available from: http://www.cronosoft.com/