To Format or To Delete

Once in a while, we have Beginners ask about the best way to make their flash media card ready for next use in the camera. 

  • They wonder whether they should delete the photo files using the delete menu of their camera vs delete feature of their computer.
  • They wonder whether they should format the card on their camera or format their card on their computer.
Here are some points to consider

Deletion does not re-draw / re-initialise the FAT

The File Allocation Table and the Directory Table are what what photo files are made of. If the FAT is somehow corrupted by mishap, one or more files are affected.
  • Deletion marks the relevant filename entry(s) in the Directory Table as "killed" but does not necessarily flush the filename nor the FAT entries. As you write files onto the card, these entries will be over-written.
  • Formating re-creates thefile system. This ensures that at this point in time, there is no corruption of the FAT or the DT.


  • You can "Delete All" using the camera and still have files that the camera does not understand or know about on the card. You could put music, office documents, whatever, on the card and "Delete All" from the camera might be blind to that.
  • If there was accidental corruption of the FAT / DS, deletion does not attempt to repair the corruption.
  • Deletion of all files is slower because it marks each entry labouriously, one by one. Quick Formatting simply wipes the FAT and DT.
  • In some scenarios with some computer operating systems, there is additional information that the computer stores on any media. A hidden Recycle Bin folder could be one. Mac OSX file structure forks could be another. The camera may be blind to these files and structures and deletion or operations by the camera would be blind to these structures. Meaning that your card could have hidden stuff on it taking up space and the camera would not be able to manage that without a Format
  • If you are prone to mishaps and every photo file has been deleted on the card using "Delete", there is a high possibility that computer recovery programs can undelete / undo / recover your photo files. The ability to recover after you have carried out a Format is much lower. For more reading, see Data Recovery

The Format command on the camera is likely a Quick Format

From the short time it takes to Format a card using the camera menus, the camera is likely to carry out a Quick Format - a wipe and re-layout of the file system structure rather than a Low-Level Format


  • Data Recovery might still be possible to some extent if the same card has not seen new files, has been formatted on the same camera.
  • A Camera Quick Format shouild not contribute to wearing out your card or damage your card.

Formatting / Data mishaps on the computer could cause issues

Although there is the general concept and even standard on what the FAT and filesystem is, each type of computer and camera may approach the implementation in different ways.

  • FAT is just not FAT - there is FAT16, FAT32 and other lesser known FAT standards.
  • The Olympus / Fuji xD cards had digital signatures in on the card. If these signatures were unexpectedly wiped by formatting on the computer or you had an accident with premature removal of the card from the card reader etc..., you could have card that was physically able but the camera would refuse to recognise it. 
This risk has caused the community to encourage formatting and/or deletion with the camera, not another device.

Storage Media are not Forever

Although flash memory is not a mechanical device with moving parts like a hard disk, flash memory wears down.  To counter this, flash memory is produced with wear levelling controllers.
Some people rightly say, buy memory from a respected, premium brand. This will imply that the brand / model closer quality assurance tolerances, a higher lifetime expectancy and an established warranty / return policy. In large part, that is good advice.
But there are few absolute guarantees in life. You might still encounter what we euphemistically call "a dud" despite the best quality assurance efforts. You might be paying for the brand's higher profit margin instead of higher specifications.
At the end of the day, it's your choice. 
(Comments and addendums are welcome)

 Further Links

Navigate to:

Recent Forum Discussions on Card Formatting

Recent Forum Discussions on Deleting Photos

 Ananda's Compilation of Tips

 Ananda's Photoblog 

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views and opinions held by or any affiliated companies.


Total comments: 4
By AnandaSim (Oct 5, 2011)

Factor 2c. Low level format of a card

You do not need to low level format a Flash media card. They are non mechanical and have wear leveller controllers so low level format doesn't do what we expect it does to mechanical devices like hard disks.

You can low level (binary format) a card but that's a story for another day.

Most cameras - do a fast quick high level format. The menu to format your media is quite clearly labelled and about three menu clicks on the camera. It takes all of 3 secs or something like that to process.

By AnandaSim (Oct 5, 2011)

Factor 2b. When you hook up your camera to the computer.

Please, you have paid good money for your camera. You have to stick it to your computer and the computer has to recognise the camera. It does not always work without software driver and sometimes the computer gets confused. You have to bring the USB cord. You don't always have it. The camera is big and near your elbow. Move your hand wrong and your camera falls on the floor. The camera has to be powered by batteries. If you dilly dally you are eating energy from your batteries and you forget to recharge and so on. Your precious camera becomes a second rate slow card reader. You can buy a high speed card reader for next to nothing.

By AnandaSim (Oct 5, 2011)

Hey Paul, thanks for the oppurtunity to discuss.

Factor 1: Corruption is unlikely

I disagree with that sentiment. In the digital world, if something bad is gonna happen it is gonna happen at the wrong time to the most defenceless people. I have had two Olympus xD cards become unuseable pre-Windows XP - I am meticulous about ejecting cards from the PC and still their boot sector header was corrupted. People shoot until their batteries run out. When saving that last shot if the camera conks out, the FAT is not safely written and you have file system corruption. Etc

Factor 2a. Using your camera's file transfer program
I was with a colleague who has a Nikon D90 and stuff at home but at the office he could not find or did not have his Nikon software. He had trouble figuring out how to get it from the website and if his corporate workplace machine had been locked down by IT, he would not be able to install any software. The more dependencies you create in a chain, the more you cause angst

By PaulRivers (Oct 4, 2011)

I think there's 2 other factors to consider -
1. What the likelyhood of these card issues happening actually is, as some of things thing like corruption of the file system seem rather unlikely.
2. You can save a lot of time by setting up your cameras file transfer program to automatically copy your files then delete them off the card when you hook your camera up to your computer or insert your card into your card reader, but I do not believe you can get it to do a low level format on the card, if you want to do that it takes more of your own time to go through the cameras menus and do it.

Total comments: 4