Wednesday, 18 June 2014

To Format or To Delete

DPReview.com is shutting down their user articles section. I wrote this Sept 30, 2011

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 the file system. This ensures that at this point in time, there is no corruption of the FAT or the DT.
Implications
  • 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 laboriously, 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

See High-level Formatting and Reformatting vs Low-Level Formating

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

Implications
  • 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. 

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