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Photo Recovery of Overwritten Files

Question
I was happy that I was able to recover some pictures (of my 7 month old baby) from my photo memory card that I accidently formatted using the complimentary ZAR digital image recovery software on line. However, some (probably 160 of them) were not recovered. Is it possible that I overwritten them when I took more photos on the same card and "protected" the new pictures after I accidentally reformatted the memory card? If that is the case, is there another software available to retrieve them?
More info:
  • There were about 200 pictures before the format.
  • The card was not at capacity before format, probably less than half filled because I only have had the card since November.
  • After I formatted the card, I took about 160 pictures.
  • The latter pictures that I took (before the formatting), I was trying out higer resolution, but not sure about the compression settings.
  • I was able to recover the more recent shots than the earlier ones (before I formatted the card) however, so does that mean there's a chance of recovering the earlier shots? (to be hopeful).
Answer
Something that was overwritten can't be recovered, ever. This is by the nature of a (flash-like) digital memory, which does not have any remembrance of its previous state. So we just need to compare how many files we expect overwritten with what we got. Also, as the card fills up, you delete files from it, and take more shots, the shots taken last tend to fragment - i.e. they are stored in several nonadjacent blocks, rather then contiguously. Fragmented image files typically cannot be recovered after format. So, I'd say there is nothing more in there.
  1. Originally, there was 200 pics on card (old layer).
  2. You formatted it and took 160 pics more (new layer), which were written over then old ones.
  3. Now there are 160 "new layer" pics, and about 40 "old layer", which is all we can recover.
  4. Taking into account the fact that "new layer" is larger res, hence larger size, I'd expect the result worse than 40 images.
Question

I'm hoping that you can help me better understand how the overwritten files work. About 2 months ago I took about 80 pictures on a shared work camera. Someone else used the camera right after me and deleted all the pictures before I got to save them. I didn't realize that photos could be recovered so I just thought that they were lost forever. Since then 1 person used the camera and took about 50 pictures and deleted them. Then another person after that used the camera and took 3 pictures then deleted them. I just found out yesterday that pictures can actually be recovered. So does this mean that it is possible for me to still recover about 30 of the pictures?

I had the IT person at my company take a look at it today with a recovery software and he could only find those 53 most recent pictures. Also, so you know this is a 1 GB memory card and it was never filled up. Would the 53 new pictures overwrite older pictures before overwriting my 80 more current pictures? And do they take up the same amount of space? The settings were the same on all pictures taken. The resolution and compression weren't changed.

Answer
There are couple of additional considerations:
  1. If you format the card, the camera may overwrite the card entirely with zeros. Canon Powershot series tend to do this, and maybe other models I don't know about. Consider testing your particular camera with a spare card - not the card you need to recover from. Take a couple of shots, format the card with the camera without changing settings, see if something is recoverable. Also if you have a "Delete all" option, try this as well.
  2. Photo compression would produce different image sizes for different images even with the same settings. This depends on the content of the image. For a given compression settings, the image filled with a solid color (like a blank sheet of paper) compresses better and takes less space; on the other hand, something with many small details would use more space.

Once the pictures are deleted, they become a free space. As far as reuse of the free space is concerned, there is no "older" or "newer" free space.

Question

I have a Sony Cybershot digicam with a 4 GB memory card. I had around 150-200 pictures in it before we went for a trip. I took around 500 pictures. After the trip, my friend accidently deleted all the pictures in my camera and copied 270 pictures of her camera into my memory card (through laptop). Luckily, she had already copied the pictures I took with my camera during the trip, but I now have no backup of the 150-200 personal photographs I already had in it. I've tried various software including ZAR. They do recover a few of my photographs of the trip, but none out of the previous ones. I'd be really grateful if you could tell me any way of recovering my lost pictures.

Answer

Taking into account all the previous considerations and that fact that you have already tried several different tools and no results, I don't expect the pictures to be recoverable. Different software uses slightly (or sometimes significantly) different methods, but if none worked, there is nothing left to try.

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