How often should memory cards be formatted?

Question

Should memory cards in DSLRs be formatted every so often? If so, how often?

I hear that after emptying the card out (transferring images to a computer), that it's a good time to format it to help reduce the chance for error/corruption. Is this true?

I want to point out: Nikon D90 User's Guide by Ken Rockwell

From the site:

Always format your card after you put it in any camera, or if you've connected your camera to a computer.

Formatting your card(s) ensures any folder or file corruption acquired anywhere goes away.

You can shoot without doing this, however constant formatting is good practice and should eliminate ever having any card errors. Be sure you've downloaded and backed up all the files in two different physical locations before formatting.

Answer 1

I format my card every time I stick it in my camera and start a shoot.

I do this for a couple of reasons.

First, it means every time I start a shoot, I don't accidentally leave the previous shoot on it (and it also means I don't delete it until I start the next shoot, by which time those images are safely on various backup disks; gives me an emergency backup on the card until I'm sure I've got multiple copies elsewhere).

Second, I use multiple camera bodies, and I know people who've had corruption issues with cards formatted by the computer (which I never do) or by one body and used in another because the bodies interact with the card slightly differently. By formatting every time, I know the formatting is what the camera wants and is expecting.

Third, formatting at the start of the shoot will (or should!) catch a card that is starting to fail. At the least, it'll catch some early failure modes in the card -- and in two cases for me so far, it has. So if the card hits an error during format, I know to immediately retire it. I'd rather find out I have a card error at the START of the shoot that midway into it, or worse, when I'm trying to read the images out later.

Note: any time I get a card error, I retire that card. Cards are cheap. Dead cards that eat my only copy of an image is expensive. And formatting a card every time means that every time I shoot gives me a blank slate in a known state that hasn't reported an error. Which means many fewer potential problems later. And FWIW, I basically never run into corrupted cards, lost images or problems during a shoot or during a post-shoot import.

Even if it means the card will wear out sooner, I don't care. I want reliable cards, not ancient ones. I'll happily replace them rather than try to recover images from them....

Answer 2

I would see no reason to format the card on a regular basis, simply erasing all images on the card is sufficient. Bear in mind that most flash based media have a limit on the number of writes and so formatting is going to help you reach that limit a little bit faster.

The only upside to formatting, which is probably where this idea came from, is that it can be faster than file delete. That I might do if the card was full or close to it. However, if I'm transferring anything less than half the capacity of the card, I'd probably just erase the files afterwards.

Answer 3

I format my card in-camera before every use. I use the USB cable and never take the card out of the camera unless I fill a card on a long shoot/trip. I've never had a problem, but I can't say that's because of my procedure. Seems to be a lot of hearsay about what the correct procedure is :)

So here is what some manufacturers have to say.

Nikon

Memory cards need occasional maintenance, too. Every Nikon digital camera offers an in-camera format option. Formatting the card in-camera not only deletes the pictures, it creates a new directory on the card. This can help to avoid problems that might prevent the card from being read by your computer. Some people format after each download, once the photos are safely transferred to the computer. Others choose to do it once a month. The important thing is to do it regularly.

Olympus

Memory cards should be formatted to maintain top performance. They should only be formatted using the camera—never format using a computer as it may render the card unreadable by the camera.

Formatting clears the directory structure of the card and removes any artifacts that might be left behind by erasing. Repeatedly using the ERASE and ERASE ALL camera options and not formatting can result in a buildup of file artifacts that may eventually cause the card to fail. Be sure to download and save any images on the memory card before formatting

Sandisk (refers to Mac)

When using a memory card, it is recommended to reformat the card in the camera instead of formatting it through your computer

Answer 4

The camera will only ever do a "quick format" as there is a limit on read/write operations on flash memory.

Personally, I use several cards in rotation, and format immediately prior to needing it again -- the benefit of this approach means that when my hard disk died last year, I didn't lose any files, as I could download from card again (and restore older pictures from backups)

Answer 5

Memory cards are FAT formatted. When a file is deleted in FAT, the space is marked as free, but there can still be hidden fragmentation and corruption. Formatting rewrites the allocation table to make sure the space is continuous and you don't have any file-system errors.

As a precaution, I do it every so often especially when burst shooting when I never want to be limited by write speed.

Answer 6

I use my computer to delete photos from the card after importing them. I NEVER reformat the card. For me it is useful to not reset the camera's image counter that generates the file names for images on the card. This lets me add images to my photo gallery on my computer without file name collisions.

Answer 7

Yes, memory cards should be formatted now and then, but it doesn't have to be very often.

If you format it every time you empty it, you will perform write operations to the same part of the memory, which shortens it's life span. So that would actually in the end cause corruption instead of fixing it.

When you delete files, the data is left on the memory card but marked as reusable. When you create new files it will first use sectors that hasn't previously been used, so this will spread the usage so that new files aren't always created in the same place, which prolongs the life time of the memory card. When you format the card, this information is removed. So if you format the card each time you empty it, new files will always be created in the same part, also reducing it's life time.

Formatting a memory card doesn't reduce the chance of corruption, a newly formatted card is no less prone to get corrupted. It will however fix corruption if it's already there.

When you create and delete files on the memory card, the directory entries are not removed but left to be reused. Over time this can accumulate, and formatting will regain this space, but generally it's only a few kilobytes so it's certainly no reason to format often.