compact flash memory card

 

<p>I have a 2gb compact flash card which i use on my Sony dslr camera and it always has like around 400 - 500 available recordable images..... Anyway 2 days ago i turned on my cam and it only has 10 images availale to take but the card is totally empty.. GRRRRRR! How frustrating, inserted the cam on my Mac and it say the card has 1.86 GB used and 45.7MB availbale what rubbish is that ?<br>

Do i need a new card or is there a way i can fix this .... Please help</p>

 

<p>Try formating it.</p>

<p>If it has almost two gigabytes used, then it can’t also be empty. What’s on it that isn’t photos? Connect it directly to the Mac instead of through the camera and you’ll see what there really is on it. It might have stuff you actually want, so do that before you decide to format it and lose everything that is on it currently. If you haven’t got a card reader, get one first – they’re very useful to have around in the long run.</p>

<p>By chance, you haven't been too close to your refrigerator (nice magnets often rest there) or near a few large loud-speakers, have you? Since you did not mention the name brand of your CF card, that could be a problem as well. SanDisk or Lexar generally are OK, but if you save $$$s to buy a off-name-brand, you take your chances.</p>

<p> </p>

<p>Just how are magnetic fields supposed to affect CF cards? Solid state magnetic bubble storage systems never caught on.</p>

<p>Short of high energy EMP there's not much that can corrupt data on a CF card when it's not powered up. People have put them though the washing machine and the data hasn't been affected. They've been dredged up from the seafloor without damage.</p>

<p>Maybe in the core of a superconducting magnet something could happen (the ones that can levitate frogs and not harm then!), but there's no way a 'fridge magnet is going to do anything.</p>

<p>How it got screwed up is hard to say, but either it's an internal circuitry failure or it got screwed up in the camera due to some software/hardware glitch and needs to be reformatted.</p>

<p> </p>

<p>Bob, see this <a href="../canon-eos-digital-camera-forum/00Vnkr">forum</a>. Flash memory cards store data as an electrical charge on a small piece of metal surrounded by in insulator. Apparently magnetic fields can induce enough electrical charge in the flash memory to corrupt or erase data and can potentiallly destroy the memory. Static DC can also do this and it is also possible that a computer glitch could have corrupted the data. </p>

<p>If the card is corrupted your only choice would be to format it. Another possibility is that the cameras was accidently powered on for a time and the shutter button was was accidently pressed causing the camera to countinousely take photos until the memory card was full and then it automatically powered down. If you connect the card to a computer do you see any files on the card or does the computer show no files and a full card. No files and a full card is a clear indication of corruption. </p>

<p>If the card doesn't work correctly after formating you need a new card. </p>

<blockquote>

<p>Flash memory cards store data as an electrical charge on a small piece of metal surrounded by in insulator.</p>

 

</blockquote>

<p>In a sense maybe, but actually electrons are held in a floating gate which is part of of a particular type of transistor structure. I suppose you could cause some erasure using a changing magnetic field since such a field will induce a current (and hence produce a voltage voltage) in any conductive structure inside the CF card and if you start inducing voltages within the chip (which is why I mentioned EMP above) you could change the state of charge of the floating gate (or blow out the structure entirely)</p>

<p>However I suspect that you'd need a pretty strong changing magnetic field. Stronger than a fridge magnet (and just holding a CF card close to a strong magnet won't do anything).</p>

<p>I have some old CF cards with very low capacity. Maybe I'll sacrifice one and see if I can alter the data using magnets. I have some very powerful rare earth magnets I can try and I'm sure I can dig out some old electromagnets which will produce an alternating magnetic field when driven with AC.</p>

<p>I'll be very surprised if the data gets corrupted with any casual contact with magnets. With enough of a changing field I'm sure you can get changes, but I suspect that field strength is not something you'd ever accidentally encounter. It's like an RF field. Normal radio transmitters, cell phones etc. typically won't erase a CF card. However all bets are off if you put one in a microwave oven!</p>

<p>Reformat the card in camera and see what happens.</p>

<p>As for Cellphones, etc... I routinely carry mine in my pocket with memory cards and haven't had an issue.</p>

<p>Dave</p>

 

<blockquote>

<p>However I suspect that you'd need a pretty strong changing magnetic field. Stronger than a fridge magnet (and just holding a CF card close to a strong magnet won't do anything).</p>

</blockquote>

<p>True a standard fridge magnet is probably not strong enough but that said rare earth magnets are becomming more common and I have heard of them being used in some speakers and fridge magnets. Some rare earth magnets are increadably powerful. But that said I honestly think a AC magnet will be more damaging.</p>

<blockquote>

<p>In a sense maybe, but actually electrons are held in a floating gate which is part of of a particular type of transistor structure.</p>

</blockquote>

<p>Correct, I just simplified by explaination for those not familure with the technology.</p>

<p>Thanks guys I went in Jessops and they told me to format the card. Something i had never had to do before, but the bloke in the store went on the camera's menu and chose the format option! well it worked. :-D</p>

<p>Cheers pips</p>