Hi

General advice is to only let the camera erase and format cards. Not
everyone uses quite the same 'standards' when setting up cards in cameras,
and one computer's version of empty may not match with another. More card
problems are caused by computers writing to cards (which is what erasing is)
than ever happen 'in camera'.

CF cards are much better in this respect than SM cards, which rely on having
the some of the memory controller electronics in the reader. I lent my E20
to a friend to 'try out' digital and they managed to corrupt 4 128M SM cards
by 'erasing' them with some bit of PC software they had used to sort out
files :-(  fortunately someone else with a PC and Belkin reader had the
reformatting software to revive the cards :-)

Interrupting power or pulling out the card during read/write operations is
also likely to corrupt memory.

Cards are not affected by magnetic fields or X-rays, well certainly not at
levels likely to be encountered in day to day life. They are drop sensitive
like most electronic items, but once again more likely to a 6 foot drop onto
concrete rather than a gentle tap. They are also sensitive to ESD (static
electricity), so changing a card just as you get out of a car on a warm dry
might not be a good idea.

Incidentally flash memory has a limited number of writes to it. The internal
memory management circuitry is designed to spread out the locations on the
chip(s) that data is written to, so as to maximise usable life. Otherwise
the file directory and start of the storage area would 'wear out' first (how
often do you completely fill a card?) In normal usage this is not worth
worrying about, since you will probably wear out several cameras first.

There is probably no good reason to erase and then format twice unless you
are specifically trying to see if you can wear out the cards :-) :-)


More info at:
<http://www.compactflash.org/faqs/faq.htm>
Where you can find that the CF2.0 standard supports up to 137GB at a maximum
of 16MB/sec - that's over two hours to download your days shoot ;-)


bye for now   

Keith Cooper

Northlight Images
http://northlight-images.co.uk
Photography - Digital Imaging - Apple Mac Consultancy

Tel +44 (0)116 291 9092 Mobile +44 (0)780 162 9397


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