Do you "erase all" pics or format your card on a 20D after transfer?

I once used a 2GB CF card to transfer a large file between 2 computers with CF readers. Next day went out to take photos of a friend's opening concert for her first CD release. I used erase all to get rid of a couple test images and was quite suprised when after only 40 or so images, my 2GB CF card was full! Couldn't erase the large file I transferred with the camera without formatting and loosing the 40 images I already had. Since then I always format the card (as well as a second CF card)!

Low level format is used on magnetic disks to create the sectors with preamble, data and postamble sections. If a bad sector/track is found then an alternative one is used. We, regular users, never do that nowadays.

 

In MS-DOS et al, the regular format checks for sectors consistency (that is why it takes a long time) and writes a file system structure, if a bad sector is found it is not used. The quick format only writes the file system structure.

 

The name is misleading, in UNIX it is called to MaKe a File System (the command name is mkfs), in MS-DOS is called formating the disk.

 

If you only erase files the liberated sectors go to a "free list" and if later some pointer is lost, the file system has more probabilities to became corrupted.

 

If you "format" in camera (re-create the file sistem) you avoid posible fragmentation, you have less posiblities of file system corruption (it is used only once) and you know it is 100% compatible with the FAT interpretation of your camera because your camere wrote it. Haven't checked on camera, but in very populated hard disks "formating" is usually faster than erasing all the files.

 

If you have a clean new file system each time, if you need to unformat it is easier and faster.

 

Moving is dangerous, it is a copy with a implicit delete, but if the copy fails but the system is not aware of it, then it deletes the source files and you have nothing on hard disk and nothing on memory card (you can try to undelete the files on the card)

 

In brief, I copy from the card to the hard disk using a card reader. Then copy form first hard disk to second hard disk (external), then I put the card into the camera and format it. Later backup on DVD from time to time.

 

Sorry for the long post.

Formating a CF card does NOT delete the file only the header. If you use a CF recovery program you can 'recover' all the images as I have found when I accidently formated the wrong card.

I "copy", not "move" files from card to computer, erase in camera, and then format, on the advice of a camera shop techie in Santa Barbara who told me that some of his customers had various card problems later if they didn't, one frightening one being the shots showing up on review in the LCD screen, all OK looking, then nothing showing on transfer to computer

 

It's worked fine so far, one 256 MB card has been used at least thirty times with no problems