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Old Jan 18, 2013, 01:18 PM   #1
jojoba
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Can I set up a Mac to permanently delete everything on a memory card?

I'm pretty frustrated right now, I've just learned the very hard way (i.e. by messing up a research project) that mac doesn't actually delete files on a memory card if you delete them, it just hides them.

I've also found that the solution is to empty the trash bin while the memory card is still inserted into my Air. (If there are any better solutions around, please let me know).

Is there a way to change these settings, so that selecting the files and just pressing delete permanently deletes the files? I'm dealing with ten memory cards on a daily basis, so it would be a whole lot more convenient if I wouldn't have to do the additional empty trash operation for every card.
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Old Jan 18, 2013, 01:22 PM   #2
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How did it not deleting your files cause you any grief?
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Old Jan 18, 2013, 01:28 PM   #3
jojoba
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Originally Posted by blueroom View Post
How did it not deleting your files cause you any grief?
We're running a research project where different groups of people are recording different things in different locations, and the recordings would stop long before we expected, saying 'card full'. In some cases, we could step in and fix it, in others we couldn't. But basically, we thought we were giving out empty 32GB memory cards when, in reality, some of the only had a few gigs free, so we didn't get to record all the data we needed. I am pretty livid about it at the moment.
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Old Jan 18, 2013, 01:51 PM   #4
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This is not just a Mac thing.... All cameras I know about recommend formatting cards in the camera and not in the computer.

There is a difference between 'Formatting' and 'Deleting'...

When you are deleting, both OS X and Windows leave the files on a disk (or card) and simply rewrite the file directory as being 'empty'. In a computer, the OS will then overwrite the new files onto the areas where the old files were/are.

Often a camera does not work the same way. It can't 'see' the old deleted files, but it doesn't seem to be able to write new files onto files that are simply deleted. I would guess this is a safety check. If you accidentally corrupt the file directory, the (valuable) images are still retrievable.

Formatting is different than deletion, in that it is more thorough. I don't know for a fact that using disk utility will work better, but it is worth an experiment. Keep in mind that it may work for one model or make of camera, but not another.

Like I said... camera makers recommend that you format the cards in the camera and not in the computer. After all, the OS that runs the camera is completely different (and written by different people with different priorities) than the OS for a computer - whether OS X or Windows.

Good Luck.

ps A lesson in why thorough testing of all phases and factors is important....
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Old Jan 18, 2013, 02:16 PM   #5
jojoba
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Originally Posted by snberk103 View Post
This is not just a Mac thing.... All cameras I know about recommend formatting cards in the camera and not in the computer.

There is a difference between 'Formatting' and 'Deleting'...

When you are deleting, both OS X and Windows leave the files on a disk (or card) and simply rewrite the file directory as being 'empty'. In a computer, the OS will then overwrite the new files onto the areas where the old files were/are.

Often a camera does not work the same way. It can't 'see' the old deleted files, but it doesn't seem to be able to write new files onto files that are simply deleted. I would guess this is a safety check. If you accidentally corrupt the file directory, the (valuable) images are still retrievable.

Formatting is different than deletion, in that it is more thorough. I don't know for a fact that using disk utility will work better, but it is worth an experiment. Keep in mind that it may work for one model or make of camera, but not another.

Like I said... camera makers recommend that you format the cards in the camera and not in the computer. After all, the OS that runs the camera is completely different (and written by different people with different priorities) than the OS for a computer - whether OS X or Windows.

Good Luck.

ps A lesson in why thorough testing of all phases and factors is important....
Thanks for all that, I'll check out disk utility!

We had to do the work with the files on computers, because the cameras were constantly on the move in the field - so we just met for quick hand overs exchanging memory cards, then handing the camera on to new people. We don't really have the budget at the moment to double the number of cameras - although now that I've understood how to properly delete, this hopefully won't be an issue for the next round.

When I googled it, lots of sites specified this as a 'mac thing'. I haven't had the same issue before on my Windows work pc. Anyway, now I know how to avoid it in the future. We did quite extensive testing - but didn't film enough on a single memory card to go over 32GB. Well, you live and learn
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Old Jan 18, 2013, 03:39 PM   #6
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If you...

dont need formating the card, but really destroying the data in it, maybe you can use PGP desktop for Mac. There is a free version I currently use to really erase files I dont need any longer. And I have the understanding this software can work in any device capable of be mounted in the desktop....


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Old Jan 18, 2013, 05:39 PM   #7
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Originally Posted by jojoba View Post
...We don't really have the budget at the moment to double the number of cameras - although now that I've understood how to properly delete, this hopefully won't be an issue for the next round.
...
Just train and/or give instructions to each team to format the card in their own camera at the start of the session. It takes only a few seconds to do. Then it's formatted, and the team knows that the card is actually in place.
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Old Jan 19, 2013, 01:33 PM   #8
Dave Braine
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I've also found that the solution is to empty the trash bin while the memory card is still inserted into my Air.
That's the way it works on Macs. Not only for memory cards but also for USB sticks/thumbdrives and external hard drives.

Delete on the memory device, then empty the trash. Only takes a few seconds.
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Old Jan 19, 2013, 04:19 PM   #9
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Originally Posted by jojoba View Post
Is there a way to change these settings, so that selecting the files and just pressing delete permanently deletes the files? I'm dealing with ten memory cards on a daily basis, so it would be a whole lot more convenient if I wouldn't have to do the additional empty trash operation for every card.
I use cmd-shift-delete to empty the Trash (it's under the Finder menu). If I used cmd-delete to move them to the Trash in the first place, this takes me less than one second more. If there are thousands of items to delete, it then takes a little while to actually delete them before I can eject the card.

For ten cards, I can't imagine this taking a long time, unless there are thousands of files to delete when the Trash is emptied.
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Old Jan 20, 2013, 11:13 AM   #10
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Thanks, everyone. I hadn't picked up on those short cuts, that's very handy.

We're giving people as little training as possible, due to practical restrictions on how long we can interact with the informants, so I think the best solution is me just deleting (properly deleting, next time around...).
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Old Jan 20, 2013, 02:07 PM   #11
Dave Braine
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We're giving people as little training as possible
Hmmm...not always the best way.
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Old Jan 21, 2013, 11:19 PM   #12
ThirteenXIII
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Originally Posted by phoenixsan View Post
dont need formating the card, but really destroying the data in it, maybe you can use PGP desktop for Mac. There is a free version I currently use to really erase files I dont need any longer. And I have the understanding this software can work in any device capable of be mounted in the desktop....


i dont recommend PGP, it has had adverse affects on OS X 10.8, FileVault 2 is the better encryption utility.

you can also encrypt the drive with a password by right clicking and select encrypt.

and the only the way to delete items that bypass the trash are if theyre network drives..which of course is not the case.

in addition, the only other option to delete something with bypassing the trash is if the permissions were different for the drive or the file itself. -- so let OS X do its thing and not mess with its current craft

Last edited by ThirteenXIII; Jan 22, 2013 at 06:38 PM.
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