empty compact flash card with no free space?

I have a digital camera which takes compact flash cards. I offload the photos into iPhoto via my USB card reader then delete the images. Snag is it's not freeing up the space on my compact flash card. It's still showing up as full when I put it back into my camera.

I've been trying to find a way of formatting the card from my MacBook to clean it off completely but having no luck at the moment. Could someone point me in the right direction please? I have a feeling I may be missing something obvious here!

 

Usually you can format the flash cards from your camera. I'm sure there's also a way to do it through OSX but I wouldn't know. My camera can format its own memory and the flash card. So check your camera's options and see if you can do it from there (unless you've tried this already).

 

I recommend that you use your camera to erase/format your cards. I have had several experiences in which when I used the card readers on my computers to erase files on the cards, the cards becomes corrupted. Since then, I've used only the camera to manage the files and have never had a failed card since.

 

That's another thing that I find deficient in the Mac, no built in media card readers.

 

snag is.. when I put the card back in my camera and switch to it to take a photo it says memory card full.. but when I switch it to play mode, where the delete all option is, the delete all option is greyed out as if the card is already empty. I'm pretty certain there's the _trash folder on the card still which may contain files but unless I put it in my pc I won't know for sure.

I can sort it out on my pc desktop no problem but it would be nice to find a solution to this for when I'm out with my MacBook taking photographs! Is there a way of wiping/formatting harddrives/external storage devices from a mac as this might work?

 

hook the card back up to your mac and check the trash, they will prolly be there, so empty the trash.

OS X maintains the trash for devices ON the device.

 

aah cracked it... I tried emptying the trash from that card and that freed up 40mb but that was it the rest was still showing as used space.
Then I remembered the disk utility program in OS X and that did the job. I erased the "disk" using MS-DOS format. That wiped the card and freed up all the space back to it's full size and when I put it back in the camera it worked fine.
I'm not sure what I'd done to get that used block on it in the first place but if I remember to empty the trash after I've deleted the images and before I eject it then perhaps that will stop it happening again!