I occasionally get asked whether I delete images from the back of my cameras, but like most other questions relating to photography: the answer is usually both “yes” and “no”. This one of those underlying workflow things that we usually don’t think about much while we’re working, but every now and then stopping and thinking about the process you use can save you a lot of time (and sometimes pain).
My usual workflow is to shoot, take the card(s) to a computer and download them, back those images up onto a second drive, and then put the card back into the camera and Format.
I use the camera’s Format function on the cards rather than an Erase All function, because it’s:
- much faster,
- puts much less wear on the card’s “FAT” sectors (prolonging the card’s life), and
- initialises the card’s filesystem every time.
I have never (knock on wood) had a problem with a corrupted memory card. But most times I’ve encountered someone with a corrupted card it turns out that they’ve never heard of Format, and either erase images in their computer’s card reader or in the camera. After hundreds or thousands of file creations and deletions, eventually something gets confused, and then the FAT filesystem used on these cards isn’t very robust. In those cases we’ve been able to get most if not all of the images back by immediately ceasing to use that card until it can be processed by specialised image recovery software, but that’s an unnecessary pain. It’s much easier to avoid the corruption in the first place.
Don’t be afraid of the big bad Format
The other reason I’ve heard as to why someone hasn’t used Format, is because they weren’t confident. It seemed like such a final and scary thing to do. What if there was something there they hadn’t saved? Just deleting selected images seemed like a safer option to them.
Note that I don’t keep images on the cards long-term (except for those seldom-used cards that have been waiting a long time to be formatted: I usually only format as the card is inserted into the camera). I generally format with the camera rather than from the computer, because it:
- lets me leave the files on the card for longer just in case there’s a disaster, and
- gives me confidence that the camera will have set the card up the way it wants it.
Because I’ve copied all the photos from the card to my computer (and backed them up to multiple drives), when I’m invoking Format I shouldn’t be stuck wondering if I’ve backed them up. I do first check what images are on the card just to be sure, but then go ahead and format.
Now, I have (about 15 years ago with one of my first digital cameras) accidentally formatted a card, but learnt that lesson very quickly. Then in 2010 I did it again (but this time didn’t lose any images). I’ve told this story back in 2012, but it bears repeating.
I was on Deception Island in Antarctica, and we had spent about an hour traipsing around during a blizzard. I had about 60 photos in my main camera, and had just entered a building to shelter and to take more photos. The base had been over-run with volcanic ash (the entire island is the rim of an active volcano) so there were lots of photo opportunities.
You’ll notice there are rain covers on my cameras. My fingers were cold, I was tired, and somehow while setting up my camera (a 5D MkII) for Live View I pressed the wrong button and ended up in the Format menu. I panicked and tried to cancel out of it, but somehow ended up pressing OK. It was a sinking feeling watching the progress bar race across the screen. But I knew what I had to do. I took the 8 GB card out and swapped in a fresh card for the rest of the outing. I set the formatted card aside and when we were back on our ship I used photo recovery software on my laptop to recover the images, then put that card back into circulation. I got all the images back with no problems.
The recovery software I’ve used for years has been PhotoRescue, but there are many other options. Both SanDisk and Lexar provide vouchers with their “pro” cards for software downloads. This software can cope with accidental formats as well as corrupted cards, so if there’s a free or cheap option that works on your computer I recommend you install it before you need it. There aren’t many options to download new software when you’re on a remote island in Antarctica! Note that if your memory cards are larger than 32 GB your recovery software will need to cope with the “ExFAT” filesystem as well as the FAT32/FAT16/FAT12 filesystems used on smaller cards.
“Low-level” formatting SD cards
This applies to SD, SDHC, or SDXC cards. You won’t see any mention of it with CompactFlash cards (such as that screenshot above). But with the SD cards you will usually see an extra checkbox to enable a low-level format.
That little checkbox should only be ticked the first time you format a card! It will take longer than a normal format, and because it will initialise the whole card it means that you won’t be able to recover from low-level formats. I do a low-level format when I get a new card, but then format it again with that box unticked. From then on it will default to being unticked (a normal format which you can recover from).
If you’re going to give away or sell an SD card you may want to do a low-level format on it to fully wipe it, but remember to untick that box on the next format so you don’t keep doing low-level formats on all your cards.
Swapping cards between cameras
I mentioned above that I prefer to format the cards in the camera rather than in an external device. I currently use three cameras: an EOS 5D MkIII, an EOS 7D MkII, and an EOS M2 (for infrared). As long as a card has been formatted in any one of these I’m happy swapping the card to another camera if needed without needing to reformat it. I might not be confident doing this if the cameras were different makes. Also some of the older models don’t support the larger memory cards (there were compatibility issues when we passed 2 GB cards, then 8 GB, then 32 GB) but the cameras I’m using are of similar vintage.
This is of course an important part of all photographers’ workflows. Not every image is a winner. But it’s important to do this in a way that’s both safe and efficient.
Most images I take make their way through to a Lightroom catalog (having been backed up to secondary storage, etc), where I use a system of marking images for deletion (either with the Reject flag or with a special label) and then later reviewing those images to make sure I didn’t make a silly mistake, and then deleting them all in a batch (they get deleted from the disk as well as from the catalog, and a later sync will remove them from secondary storage). Doing things this way is both safe and efficient (even though we do spend a bit of power generating previews for them). I don’t try to gauge precise focus and exposure details using the camera’s LCD. That’s what Lightroom and a proper screen are for.
If I’ve been photographing a bird flying towards me and have a burst of images being saved to the card, not all of them are guaranteed to be in focus. Occasionally I’ll know as the photos are taken that the focus was completely wrong (and sometimes I’m able to fix that mid-burst). Or when photographing dolphins “porpoising” beside our boat there will be many “misses”. But I don’t have time to go back and delete individual images. For a start I’d probably miss the next animal! I’ll sort them out later, and I should have enough memory cards with me to last the outing.
However, I do sometimes delete images from the camera. If I’ve accidentally taken a photo of the inside of my lens cap, or of my foot, during an idle moment I might delete those photos to save a tiny bit of space and to streamline the later processing. Those are easy decisions to make: there’s no need for me to guess if they’re in perfect focus for example.
But I won’t sit there scrolling through all the photos looking for images to delete. That’s a waste of my useful time in the field, and just increases the odds of filesystem corruption (although because the card was freshly formatted and will be again after this card is downloaded, those odds are small).
Erase All does have a use
I even use Erase All occasionally. Like most of us I have been known to make mistakes: as well as the afore-mentioned accidental format, it’s included occasionally forgetting to format a card before shooting. Once you realise this (sometimes because the “fresh” card is suddenly full) you can either:
- take the card out and deal with it later (which can take a large amount of storage out of your day),
- throw away the new photos you’ve just put on the card, format it and move on, or
- erase all the old photos (keeping the new ones).
When using a camera that has only one card slot, the way I deal with this is to use the Protect menu function to set all the new images (the ones I want to keep) to “locked” (read-only) and then invoke Erase All (which will only delete unlocked images). These examples are from an EOS 7D MkII.
Drill down far enough into the Protect menu and you get to mark each image you want to keep (see the lock symbol on the top line in the next pictures). You can also access the Protect function using the Q function when viewing an image in playback mode.
Once you’ve protected the images you want to keep, it’s time to delete everything else.
It takes a bit more time than formatting but it preserves my new photos without wasting space and as long as I remember to format the card next time, everything Just Works.
Image Copy instead of Erase All
The 5D MkIII and 7D MkII cameras have two card slots, which gives us another option to deal with this problem. I usually use these cards in turn: automatically switching to the next when a card fills rather than being stuck with “CARD FULL”.
Consider the above situation of forgetting to format a card before shooting some new photos on it. Then having switched to the other card to get through whatever action I was photographing, when I get a spare moment I go back to the problem card and use the “Image copy” menu function to copy all the new photos from there to the other card.
In the above image you can see I’ve marked 38 images to be copied.
Once that’s done I can format the card they came from (in the above example it’s card 1: the CompactFlash) and move on with a freshly-formatted card.
Canon cameras with this “Image copy” function include the EOS 1D MkIII, 1Ds MkIII, 1D MkIV, 1D X, 5D MkIII, and 7D MkII. Nikon cameras with two slots have an equivalent “Copy Image(s)” function.
As you can see, the answer is rarely as simple as “yes” or “no”. “Sometimes” or “it depends” are common answers.
I hope this overview helps you think about the way you use your cards and cameras.