Replacing Memory Cards

[Mike Farley]

I came across this article about the life expectancy of memory cards recently. The fact that older cards can fail is hardly a surprise as it has happened to most people, but that brand new cards are also potentialy unreliable is more unexpected. In theory, each position in the nand flash memory used in cards can be written to 10,000 times and the firmware within the card is supposed to ensure that these writes are distributed evenly across the card, a process known as "wear levelling". In theory, as an example this means that if a card has sufficient capacity to hold 500 images, it would be good for 5,000,000 shots. Given that many photographers have more than one memory card, this should mean that they never fail and the camera would wear out first. The shutter on most cameras is usually rated at around 100,000 to 150,000 actuations, with this figure being around twice that for pro spec models. In practice, of course, it is the opposite which occurs and memory card failure is the more common experience.

In addition to the advice given in the article, I would also add the following:

• Whenever possible, give the wear levelling a hand and fill the card near to its maximum capacity before reformatting it.
• Try to avoid filling a card to its maximum capacity.
• Delete old images by formatting the card in camera.
• Do not delete individual images, either in camera or on your computer.
• If you insert a partially filled memory card which has been used in a different camera, format the card before use.
• If the shoot is important, use more than one memory card and/or camera. Simultaneous multiple failures are unlikely and not every shot would be lost.

Possibly with the exception of the first and last tips, I cannot think of any logical reason why this would result in improving the life expectancy of a card, other than intuitively it seems to be good practice. It is based on what I have read elsewhere, but that could simply be folklore and superstition given that cards do fail unexpectedly. Fortunately memory cards are cheap enough these days to be considered as disposable items.

http://www.imaging-resource.com/news/20 ... edia-cards

[Rose]

" Do not delete individual images on your computer ..." ???

Surely not ? Once I've downloaded the contents of memory a card onto my computer, what difference does it make to the life of the card if I then delete individual images off my computer ??!

As you know I have suffered card failure - after a Club portrait session. The card failed midway through downloading into LR and I was never able to retrieve the lost images. I only use cards up to 8GB and would rather carry extra cards and have to change mid way through a shoot, than risk losing the contents of a much larger card.

[Mike Farley]

" Do not delete individual images on your computer ..." ???

Surely not ? Once I've downloaded the contents of memory a card onto my computer, what difference does it make to the life of the card if I then delete individual images off my computer ??!

As I said, there is no empirical evidence I am aware of to suggest that this does any harm, I simply prefer not to do it and always delete images in one go with a format in camera. That way only one device updates the card and there is no possibility that separate operating systems in the computer and camera will act in slightly different ways to produce unpredictable results. Call it a misconception if you will, albeit a precaution which is backed up by years of experience in IT when supposedly compatible systems are anything but.

In fact, the images are not actually deleted and all that happens is that the record of the image is removed from a directory. That is why "lost" images can be retrieved by recovery programmes as in effect they rebuild the directory by analysing the contents of the card. Even if the card has been overwritten and reformatted several times it is still sometimes possible to retrieve images as wear levelling spreads the data around the card and the same locations are not constantly re-used.

As you know I have suffered card failure - after a Club portrait session. The card failed midway through downloading into LR and I was never able to retrieve the lost images. I only use cards up to 8GB and would rather carry extra cards and have to change mid way through a shoot, than risk losing the contents of a much larger card.

A sensible measure which helps enforce my suggestion of using multiple cards during a shoot, although even a 4 GB card can hold a lot of images. Otherwise it is very tempting simply to leave a large card in the camera for the sake of convenience.

[Rose]

I entirely agree with you about always formatting a card rather than deleting images - I've always done this, but the bullet point, as written, says not to delete individual images on the computer ?? I still don't see how doing that impacts on the life of the memory card, after you've downloaded everything and ejected it !

[davidb]

" Do not delete individual images on your computer ..." ???

I think what is meant here is not to use the computer to delete files from the card before ejecting it. I deleted several hundred images from a card before returning it to the camera. Unfortunately I didn't check the card after the return to the camera until I next used it. The camera noted that I had space for less than one hundred new photos even though I had erased hundreds. I generally carry several spare cards so that wasn't a problem.

I now erase/reformat in camera!

[Mike Farley]

I entirely agree with you about always formatting a card rather than deleting images - I've always done this, but the bullet point, as written, says not to delete individual images on the computer ?? I still don't see how doing that impacts on the life of the memory card, after you've downloaded everything and ejected it !

My previous answer applies, but perhaps I can reword it to assist understanding? I cannot provide any evidence that such a practice is harmful, so it comes down to a gut feeling based on years of experience when IT systems do not always work as they should. It might be called a digital camera, but it is in reality a computer which takes pictures. Although it is described as "delete", removing something does in fact "write" to the card as an update takes place, even if it is an instruction to remove something. For me it makes sense that only one device issues update instructions as it removes a risk, however slight, that another computer system will do something differently which ends up causing an unrecoverable corruption on the card.

If you want to get properly paranoid, you could avoid swapping cards between different cameras, even those of the same make if you want to take it to extremes. There are many different combinations and sequences of possible events which might not have all been tested, and probably haven't, so you could end up getting unlucky. For me, it makes sense to be cautious, even if I cannot prove the benefit of the advice.

I hope this helps.

[Rose]

LOL... Ah of course, I actually never thought of that as it's not something I've ever contemplated doing.

[Mike Farley]

" Do not delete individual images on your computer ..." ???

I think what is meant here is not to use the computer to delete files from the card before ejecting it. I deleted several hundred images from a card before returning it to the camera. Unfortunately I didn't check the card after the return to the camera until I next used it. The camera noted that I had space for less than one hundred new photos even though I had erased hundreds. I generally carry several spare cards so that wasn't a problem.

I now erase/reformat in camera!

This sounds to me exactly like the sort of incompatibility between camera and computer which concerns me. Thanks for posting a real life example. Fortunately, on this occasion there were no detrimental consequences other than having less space on the card than you anticipated. Did formatting the card in camera sort out the problem or was the space gone for good?

[davidb]

Did formatting the card in camera sort out the problem or was the space gone for good?

Yes, reformatting in camera did sort out the problem so I still have my full compliment of five cards. I generally rotate these although on the Bleeding London project I've tended to use just two. (Although I don't now use the computer to delete images I do tend to separate days with a couple of out of focus shots of the sky and then duplicate them (with my computer) for further separations thereby using a single card for several days until full(ish).)

I've still to experience a failed card and I'm not exactly looking forward to it