What is the most correct way to delete all photos from a camera after they all have been copied to a computer:

  • to format memory card using the camera menu,
  • or simply Select All and Delete photo files from the card using a computer as if it would be just a usb flash drive,
  • or maybe some other way?

Or no difference at all?

  • \$\begingroup\$ If you want to format a memory card, then do it with your Camera-menu. \$\endgroup\$
    – RogUE
    Commented Oct 16, 2015 at 10:10
  • \$\begingroup\$ Reformatting can cause it to be non-optimal for the specific flash memory arrangement. Avoid that, if you are using the format type that the card came with. \$\endgroup\$
    – JDługosz
    Commented Jul 21, 2021 at 0:13

9 Answers 9


There's no "right" way to do this, it's what works best for you. In general, I just tend to do the "delete all" unless the card is quite full, then I may format. It's just a question of speed, I'll tend to use the fastest path to clearing it off.

Now, there are some that recommend regular formatting of the card for various reasons. I'm not in that camp, the basis for it isn't entirely sound. However, the upside is the detection of potential hardware flaws on the device. So, even if it isn't specifically regular, doing it every now and then may have some use.

Either way, I only do it after I've made two successful copies (primary and backup). I've lost images in the past by not being more careful about it, so now I take a little time to be sure.

  • 3
    \$\begingroup\$ +1 for at least two backups. Never, ever delete photos from your camera without a copy of them all on at least 2 separate computers (or say, a PC and a portable Hard drive) \$\endgroup\$
    – MGOwen
    Commented Aug 24, 2010 at 7:50
  • 2
    \$\begingroup\$ @MGOwen I have a multi-step process: 1. copy from the card to my picture directory; 2. copy the picture directory to a backup disk; 3. verify the contents of the card against the backup disk to make sure there were no errors in copying; 4. delete the files on the card, double checking to make sure it's really the card. \$\endgroup\$ Commented Oct 9, 2015 at 18:33
  • \$\begingroup\$ +1. But now in 2018, you should add an online backup as well. That's at minimum, 1 local copy and 1 cloud copy of your images. \$\endgroup\$
    – OnBreak.
    Commented Aug 23, 2018 at 14:03

I'm not sure that the effects would be different but I would say the safe bet is

'Format the memory card using the camera menu'

Just make sure you have all of the pictures saved elsewhere before you do this (accidentally wiping out photos sucks)

  1. Read your camera's manual. They usually have recommendations.

  2. Eliminate human error. Card errors of any type are much, much more more rare than you just messing up.

The format used on cards has been a standard for a long time, and modern sizes are such that what metadata or hidden files a computer might leave are pretty insignificant. If you can find a method that keeps you from screwing up and deleting stuff by accident, then the most you'll likely need to do is a periodic in-camera format, just to be on the safe side.

I'd also add another option to the list, which is letting some sort of image-library management software take care of clearing the card for you; sort of midway between the camera and treating it like a generic USB stick. I believe Lightroom has an option for this, as does Image Capture and iPhoto on the Mac.

  • 1
    \$\begingroup\$ +1 for being all too human is a bigger risk than not erasing in the "right" way. \$\endgroup\$
    – Reid
    Commented Aug 20, 2010 at 19:13
  • 1
    \$\begingroup\$ The camera manual will always recommend using the camera to format the card, as that's the only process they have any control over. Doesn't mean other methods aren't just as good. \$\endgroup\$ Commented Aug 20, 2010 at 19:41
  • \$\begingroup\$ @Mark No, doesn't mean other methods are worse, but nor does it mean other methods are better. It's just the manufacturer's recommendation, which is to say it's a good default choice. \$\endgroup\$
    – ex-ms
    Commented Aug 20, 2010 at 20:27

If you use your cards in different cams you'll notice that quite a few cameras only show pictures took with this one camera.

So if you chose "delete all" it will only delete those images it knows, made by the cam itself and you'll end up with a partly filled memory card, not being able to take as much pictures as it should.
Same if you sometimes have other files on your memory cards, which eat up space.

Another thing, if the file system ever got corrupt for any reason, delete all won't fix it, while format will fix logical file system corruption.

I'd always use format. Except maybe if the format is extremely slow, taking several minutes (like it was in the Leica M9, not sure if they fixed it by now).

Of course, in case of format everything is gone which, for me, is what I want, but if you tend to put important data or pictures on a memory card without having a backup somewhere else, might not be what you want (but you would not do that, would you).

  • \$\begingroup\$ Thanks, the point about pictures from different cameras is important +1 \$\endgroup\$
    – rem
    Commented Aug 22, 2010 at 11:37
  • \$\begingroup\$ Since the camera didn't recognize the foreign images, they were not reviewed prior to "formatting". It's not a good idea to wipe out data site unseen. \$\endgroup\$
    – xiota
    Commented Aug 27, 2018 at 8:05

Flash cards generally are limited in the number of writes rather than the number of reads (as in the MTBF is a function of writes not reads). Formatting a card is a much "cheaper" operation (in terms of writes) than deleting all the images, so it's possible that formatting the card rather than deleting may help prolong the life of your card, although in the grand scheme of things, who can really tell.

  • \$\begingroup\$ Does formatting entail fewer cell writes than deleting? \$\endgroup\$
    – Chris Noe
    Commented Aug 23, 2010 at 2:05
  • \$\begingroup\$ @chrisnoe: I don't have any numbers or links handy to back this up, but compared to deleting a large number of images, my understanding is that formatting the card would entail fewer writes, yes. \$\endgroup\$
    – Conor Boyd
    Commented Aug 25, 2010 at 1:10

Note that formatting the card as opposed to individual file-deletion, whilst the most efficient in terms of ‘how much data is written’ to achieve it, is almost negligible compared to its ‘day job’ when you’re writing gigabytes a day to it simply taking photos.

There is one additional downside to formatting - the computer will consider it to be a totally new device it has never seen before, so will ask the same old dozy questions as to how to deal with it.
If your workflow is dependant on the computer being aware of, for instance, data copy locations per card, erase after copy or not, which camera the card belongs to... etc, then format rather than simply getting the computer to file delete is far more hinderance to your workflow, for a minimal gain in potential card life.

Additionally, whilst backups are vital, I’ve never known a file read to not checksum-match without being notified immediately that an error occurred, so i would consider manual checksumming to be overkill. That being said, I’m on Mac. Windows may handle things differently.


Erasing rather than formatting will let you use a tool like photorec to recover photos off your memory card, should the need arise.

I've erased a card thinking I'd copied photos over, but actually hadn't, and photorec came through and recovered them for me. If I'd formatted, I'd be SOL.

  • \$\begingroup\$ If you just do a "quick format", it would probably be possible to recover the photos. But if you do a "full format", then maybe not. Formatting the card in the camera will usually be a quick format. \$\endgroup\$
    – vclaw
    Commented Oct 17, 2015 at 0:47
  • \$\begingroup\$ Recovery is possible with either deletion or format, though it's easier with simple deletion because many of the file system structures remain intact. \$\endgroup\$
    – xiota
    Commented Aug 27, 2018 at 7:52

Use a "verify and move" command or script of some kind, that deletes the files after they have been copied and re-checked for matching, and is fully automated so it deletes exactly those files that were just validated.

The typical move command does that one at a time, which I find less than ideal. I would rather not write to the card at all, until after all copying is done. That way there is no vulnerability to corrupt the card with a bad flush or badly-timed crash or hardware failure.


  • scan a list of files on the card
  • copy them to two locations,
  • make sure all writing is flushed and final
  • verify the copies are byte-identical
  • (optional: time delay if you don't need the card right away, until after the next automated checkpoint on the NAS, clound backup, or whatnot)
  • delete the card files, working from the same list as step 1. Not "." but the exact files copied.
  • flush and chkdsk the card
  • formally eject the media.
  • celebrate.

Formatting is best, unless you're pressed for time.

Writing to a previously used location of flash memory requires that it be erased first. By formatting, you are pre-erasing the entire space, ready for immediate writing. It also resets any fragmentation. If you rarely or never format, fragmentation can develop, which can effect write performance:

1) read speed (nice to have): reviewing pictures, and transferring them off the device.

Unlike mechanical hard drives, fragmentation does not affect the read speed of flash memory.

2) write speed (critical): taking pictures.

Even though there are no mechanical latencies for flash memory, "write amplification", (page-level rewriting), can eventually cause significant slow downs: https://en.wikipedia.org/wiki/Write_amplification

This happens when existing files need to be moved while trying to store a new file. This involves erasing and rewriting, and that has to be done in large chunks. Imagine swapping houses with your neighbor that otherwise has the same floor-plan as you.

Note that if you keep the picture resolution setting constant, picture files tend to be nearly the same size, which goes a long way to minimizing fragmentation in the first place. However, the effects of fragmentation can eventually result in noticeable slow downs. Here are some interesting test results for SSD hard drives: http://www.lagom.nl/misc/flash_fragmentation.html

  • \$\begingroup\$ @mattdm the implied answer is that you should format the flash. It should be stated explicitly though. P.S. keeping picture settings the same won't make file sizes the same, due to compression which will vary from image to image. P.P.S. this probably should have been an edit to the answer from 2010. \$\endgroup\$ Commented Oct 9, 2015 at 18:39
  • \$\begingroup\$ I have added a preamble to make the formatting recommendation explicit. \$\endgroup\$
    – Chris Noe
    Commented Oct 10, 2015 at 12:51
  • \$\begingroup\$ If you delete all of the photos you are erasing the entire space. How is formatting better than this? \$\endgroup\$
    – vclaw
    Commented Oct 10, 2015 at 13:11
  • \$\begingroup\$ If that were true, recovery tools like photorec, mentioned in another answer, would not work. \$\endgroup\$
    – Chris Noe
    Commented Oct 10, 2015 at 14:34
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    \$\begingroup\$ The edit helps answer more clearly — thanks. But, I think some of the basic facts are wrong. Erasing at the filesystem level, or doing a quick reformat, is only tangentially related to the need to erase to write in flash memory. Fragmentation is also effectively prevented by "delete all", and rare with photo cards anyway as large files are generally written sequentially. \$\endgroup\$
    – mattdm
    Commented Oct 16, 2015 at 10:06

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