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03-19-2012, 06:12 PM   #1
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Difference between "Delete All" and "Format"?

In the camera menu, there are two options that will result in a blank memory card: "Delete All" and "Format". I understand that these aren't exactly the same for all purposes; for example, if a memory card is formatted something other than FAT32, then the camera won't read it until you use Format to format it correctly. But for the purpose of blanking the card, both, one would think, do the same thing. However, in my experience, Delete All seems to take 2 to 8 times longer (depending on how many images are on the disk) to accomplish the same thing. Format is quick. Consequently, I usually use Format.

Assuming SD cards are anything like traditional hard drives, recovering data after a format is much iffier than recovering after a deletion. But, assuming I'm careful and don't "accidentally" format a card I didn't mean to, is constantly re-formatting them doing any damage? Am I shortening the life of the card by forcing extra read/write cycles (since formatting, again in traditional HDD terms, involves a write operation to put a new partition table on the device)?

Also, is there any good reason that Delete All takes so much longer than Format?

03-19-2012, 06:39 PM   #2
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I put it like this... I tend to remove my SD card from the camera to edit on the computer and windows has a tendance to leave hidden files (sometimes) on the card. also if I forget to transfer from the card and end up editing from the SD card, the editing software leaves asociated file on the card.... "delete all" will only delete all photos an not anything else. there is also fragmentation issues with copy/delete which reduces the effective size of the SD card (so I have noticed i my comparison of this very issue)

therefore I all ways re format my cards on the camera, which I believe guarentees a clean and compatible card every time. (I re format after every upload)
03-19-2012, 06:46 PM   #3
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Technically speaking, "Delete All" goes through every picture file and deletes them one by one, while "Format" simply clears the table-of-contents of the SD Card.

"Format" results in a lot less "write" operations on the card, which is desirable because flash memory is only good for a certain (large) number of "writes".

"Format" will also completely clear the card of any data the could eventually be stored on it in addition to pictures (eg. firmware upgrade file).
03-19-2012, 06:49 PM   #4
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I strongly suspect that in-camera formatting does what, in the Windows world, used to be called a "quick format". A full format of a disk actually writes every single sector on a disk. Even a relatively small, 2GB memory card has over 4 million sectors. This is the disk format you are thinking of. With this type of formatting, the data sectors are overwritten, making recovery impossible by ordinary means. Super expensive data recovery companies MAY be able to read the residual charge on the disk, or they may not.


A quick format, on the other hand, simply writes a new, empty root directory and FAT table. The data from the files is undisturbed. That's why recovery programs can work. Everything is still there, except the directory pointer to the first sector of data. Since a quick format writes very little data, it is very fast.


"Delete all" goes through the directory and deletes every file. This consists of a couple of steps for each file. First, the first character of the file name is set to a space and the directory block is re-written.


Then, the chain of sectors must be followed to determine which sectors the file uses. A 10MB file will have 20,480 sectors.


Then the FAT table must be re-written to indicate that those sectors are now available. This isn't too bad, as the FAT table contains two bits for every sector, so 20k sectors means 40k bits, or 5K bytes, or 10 sectors in the FAT table.In this case, recovery is relatively easy, as well. The program must simply find what looks like the first sector of a file, then search the directory for filenames with a space as the first character. Such programs usually then show you a list of "deleted" filenames and ask you to supply the missing first character.


That's why "delete all" can take a relatively long time, while a "format" is almost instantaneous.

03-19-2012, 06:54 PM   #5
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AFAIK Delete All is a file-by-file tagging of each filename entry, a series of random-access writes, whereas a quick Format just rebuilds the directory structure, a block of sequential writes. The latter is faster. AFAIK Quick Format and Delete All only affect the directory tree; data is still there on the card, unless you do a Full Format via computer to wipe the card clean.

Whether constant formatting is good or bad or indifferent has been debated inclusively here. I personally do NOT reformat unless absolutely necessary, which has been maybe 1/2 dozen times in the last dozen years. I use various AV devices with various memory cards. I put a common directory structure on all cards of all types, and a script to rename and move files as desired. Reformatting would obliterate my carefully-wrought scheme. So I just run the MOVE script on a card, then go away for a few minutes, and when I return, all is hunky-dory.
03-19-2012, 07:17 PM   #6
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I use format option in the camera. It's fast and accomplished what I want (an empty card). Format gets the card ready to work as it should with the camera. I also format the card before putting a firmware update on it. I don't see any reason to use the other option unless I had other files on the card in another directory.
03-19-2012, 07:49 PM   #7
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Some people will use a card in more than one device, having files on it for or from each. "Delete All" is a way of wiping just the images from the camera, without messing with anything else stored on the card.

Deletion of a bunch of files and doing a quick format (which is exactly what the camera does, along with creating a couple directories afterwards) both put about the same wear on the card, which is extremely minimal in any real world measure.

There is so much superstition about this, it's just ridiculous. There seems to be a whole cult of "YOU MUST ALWAYS FORMAT IN CAMERA OR THE WORLD WILL END" type people, and it's just silly. There is no difference between formatting in camera or within Windows (tho I'm not touching other OSes about this, who knows what a Mac might do to it). From Windows, Quick Format, fat32 file system. Doing a full format on an SD card is counterproductive - that does cause unnecessary wear.

If you do format with it in the computer, you can either create a DCIM folder yourself, or the camera will do it for you on first use. If you make a folder within it, with a name like the camera creates (e.g. 001_0101) where the first three numbers are the folder count, and the last four are the current date, the camera will continue on numbering them in sequence each day.

Bottom line, you can do either. It doesn't matter. Just be sure to use an appropriate file system like fat32, which Windows should default to for cards anyway.
03-19-2012, 09:03 PM   #8
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QuoteOriginally posted by Philoslothical Quote
Some people will use a card in more than one device, having files on it for or from each. "Delete All" is a way of wiping just the images from the camera, without messing with anything else stored on the card.

Deletion of a bunch of files and doing a quick format (which is exactly what the camera does, along with creating a couple directories afterwards) both put about the same wear on the card, which is extremely minimal in any real world measure.

There is so much superstition about this, it's just ridiculous. There seems to be a whole cult of "YOU MUST ALWAYS FORMAT IN CAMERA OR THE WORLD WILL END" type people, and it's just silly. There is no difference between formatting in camera or within Windows (tho I'm not touching other OSes about this, who knows what a Mac might do to it). From Windows, Quick Format, fat32 file system. Doing a full format on an SD card is counterproductive - that does cause unnecessary wear.

If you do format with it in the computer, you can either create a DCIM folder yourself, or the camera will do it for you on first use. If you make a folder within it, with a name like the camera creates (e.g. 001_0101) where the first three numbers are the folder count, and the last four are the current date, the camera will continue on numbering them in sequence each day.

Bottom line, you can do either. It doesn't matter. Just be sure to use an appropriate file system like fat32, which Windows should default to for cards anyway.
this is my 'old school' understanding about in device formating... (and I have mentioned it elsewhere in regards to losing photos of good SD cards). On some CNC machines that I use to operate/program (many years ago prior to network and HDD caperbilities) use to use standard 3 1/2" floppies, formated FAT32. If you formated the disk on a computer (FAT32) the disk would show up as corupted on the machine even though the computer say it fine. but if you formated FAT32 on the machine you could still copy the programs onto the disk from the computer and use them in the machine.

fair enough, this was a very old issue but I still applly the same principles today, I format my Pentax card in my Pentax and my Sony card in my Sony.

03-19-2012, 09:18 PM   #9
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There are a couple possible causes of what you're describing. The device could have been using a non-standard implementation of fat32, and only able to read filesystems of its own creation as a result. The version the device created may have been "close enough" for Windows to still use it. Of course, I'm just guessing. Every so often you hear about modern devices with issues like this, but Pentax cameras (mercifully) aren't among them. Ultra-cheap Chinese knockoff devices are sometimes prone to this kind of bug.
03-20-2012, 04:09 AM   #10
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QuoteOriginally posted by bdparker Quote
use standard 3 1/2" floppies, formated FAT32
Are you sure that that is FAT32? Even FAT12 should have been OK for those.

From wikipedia:
QuoteQuote:
FAT12 remains in use on all common floppy disks, including 1.44 MB and later 2.88 MB disks (media descriptor byte 0xF0)
03-20-2012, 07:39 AM   #11
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QuoteOriginally posted by RBellavance Quote
Technically speaking, "Delete All" goes through every picture file and deletes them one by one, while "Format" simply clears the table-of-contents of the SD Card.

"Format" results in a lot less "write" operations on the card, which is desirable because flash memory is only good for a certain (large) number of "writes".

"Format" will also completely clear the card of any data the could eventually be stored on it in addition to pictures (eg. firmware upgrade file).
this is I think backwards,

Delete All clears the File Allocation table, but leaves the data on the card, and the data is overwritten with new photos.

Format deletes all the data.

the way to test to prove this completely is to take some shots, use delete all, and then take the card out of the camera and use file recovery tools to restore the deleted files. If it is possible then the delete all will have only removed the file names from the file allocation table but not actually removed data from the card.
03-20-2012, 07:47 AM   #12
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QuoteOriginally posted by Lowell Goudge Quote
Delete All clears the File Allocation table, but leaves the data on the card, and the data is overwritten with new photos.

Format deletes all the data.
Neither actually deletes the data. "Format" clears the FAT in one swipe, whereas "Delete All" marks each file as "deleted".
03-20-2012, 10:10 AM   #13
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QuoteOriginally posted by RBellavance Quote
Neither actually deletes the data. "Format" clears the FAT in one swipe, whereas "Delete All" marks each file as "deleted".
In reality it is worse than that - the wear-leveling algorithm of the card controller is likely to just write the new FAT into a less used memory area, leaving the old one behind to be eventually overwritten. The only way to completely clear a card is to overwrite all of it with new data, a quite tedious process
03-20-2012, 10:37 AM   #14
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Most cards these days have a small second (and hidden) partition just for the FAT. The same physical area gets overwritten by formatting.
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