Eye of the eclipse...

by darkhausen

submit your photo

Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Sign up ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

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?

share|improve this question
If you want to format a memory card, then do it with your Camera-menu. – RogUE Oct 16 at 10:10

9 Answers 9

up vote 12 down vote accepted

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.

share|improve this answer
+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) – MGOwen Aug 24 '10 at 7:50
@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. – Mark Ransom Oct 9 at 18:33

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)

share|improve this answer
  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.

share|improve this answer
+1 for being all too human is a bigger risk than not erasing in the "right" way. – Reid Aug 20 '10 at 19:13
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. – Mark Ransom Aug 20 '10 at 19:41
@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. – ex-ms Aug 20 '10 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).

share|improve this answer
Thanks, the point about pictures from different cameras is important +1 – rem Aug 22 '10 at 11:37

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.

share|improve this answer
Does formatting entail fewer cell writes than deleting? – Chris Noe Aug 23 '10 at 2:05
@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. – Conor Boyd Aug 25 '10 at 1:10

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.

share|improve this answer
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. – vclaw Oct 17 at 0:47

Files stored on a memory card are organized in much the same way as a computer hard drive, and can become fragmented over time. Although the effects of fragmentation are much less significant for flash memory than it is for a mechanical hard drive, I would still recommend reformatting, at least periodically.

share|improve this answer
Thanks, good answer, +1 – rem Aug 22 '10 at 6:54

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.
share|improve this answer

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

share|improve this answer
This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. – AJ Henderson Oct 9 at 13:47
@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. – Mark Ransom Oct 9 at 18:39
I have added a preamble to make the formatting recommendation explicit. – Chris Noe Oct 10 at 12:51
If you delete all of the photos you are erasing the entire space. How is formatting better than this? – vclaw Oct 10 at 13:11
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. – mattdm Oct 16 at 10:06

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.