Safety of flash cards/question

Started Aug 23, 2008 | Discussions thread
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Ray Thompson
Senior MemberPosts: 1,221
Card Corruption
In reply to Judy Stone, Aug 25, 2008

I think it is that last image on the card that causes problems. When shooting JPG, if the camera says you have space for one more image, the camera is basing that on average compression. Some images do not compress as well. So the camera thinks there is enough space for one more image.

But that last image you took does not compress well and takes 3.2 Mb rather than the 3.1 Mb that the camera calculated. The camera obligingly writes the image to the card beyond the address space of the card. Sometimes this wraps back to the beginning of the card depending on how the addressing is accomplished in the camera.

If the first part of the card gets overwritten your card will be immediately corrupted.

So I never fill a card to capacity always leaving room for at least 5 pictures. I have never had a card get corrupted that was not due to outright card failure where the card just simply did not work anymore.

That is my theory, and it is indeed weak.

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