Recovering altered jpegs

Discussion in 'Digital Photography' started by John Tomasi, Aug 17, 2004.

  1. John Tomasi

    John Tomasi Guest

    Hi everyone,

    Is it possible to recover an original jpeg file after changing it and
    (accidentally) hitting the save button?

    My situation is this ... After adjusting the levels on a jpeg, I
    intended to save it in a lossless tiff format. However, I mistakenly
    saved it as a jpeg. I know that saving changes to a jpeg degrades the
    image, so I was wondering if the original, undegraded image was
    floating around in a temp folder somewhere.

    Any advice would be much appreciated!

    John Tomasi
    John Tomasi, Aug 17, 2004
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  2. John Tomasi

    JustaPawn Guest

    << Is it possible to recover an original jpeg file after changing it and
    (accidentally) hitting the save button? >>

    Well, if you're using Photoshop, and you haven't quit the file, you can go back
    to when you opened it or any place in between with the history palette.
    JustaPawn, Aug 17, 2004
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  3. John Tomasi

    Pete Guest

    .... or with almost any editor, simply use Undo until you get back to the
    original version, then Save As.
    Pete, Aug 17, 2004
  4. John Tomasi

    John Tomasi Guest

    Thanks for your responses, JustaPawn and Pete.

    I'm no expert, but my understanding is that because jpegs are lossy,
    everytime you click the "save" button, your image will lose data from
    your image. So, if I travelled back on the history palette and saved it
    again, I'd degrade the jpeg even further than if I just left it as is.

    I'm happy with the changes I made to the photo, so that's not the issue.
    The issue is the quality of the image file.

    Or maybe I'm just overthinking this. Is saving a jpeg once or twice that
    big a deal in terms of file quality?
    John Tomasi, Aug 17, 2004
  5. John Tomasi

    IMKen Guest

    This is the reason I always work on a duplicate of the image rather than the
    original. First thing to do when you open an image for editing is duplicate
    it and close the original.

    IMKen, Aug 17, 2004
  6. You can go the opposite route by making the folder read-only which
    will enforce renaming or releasing.
    James Silverton, Aug 17, 2004
  7. John Tomasi

    Jeremy Nixon Guest

    No, that's not the case. The jpeg compression is what loses data; what is
    still sitting in Photoshop is not changed in any way by saving it. So
    you can save to jpeg every 3 seconds and it's still only one "generation"
    of loss.

    In your initial inquiry it sounded like you meant to save the modified
    picture as a copy, and wanted to preserve the original jpeg as-is. That,
    indeed, will now require some loss due to the jpeg compression, even if
    you go back in the History and re-save the unchanged picture. However,
    if you want the picture as-is after editing, then, no big deal -- saving
    it as a jpeg will mean one generation of compression loss, not one for
    each time you hit "save".
    Save it using very low compression and you won't notice the difference.
    Jeremy Nixon, Aug 17, 2004
  8. John Tomasi

    Alan Meyer Guest

    The JPEG compression scheme takes advantage of the fact
    that the eye can't discern very slightly different colors easily.
    It eliminates very slight differences in order to reduce the total
    number of different colors that get saved in each small section
    of the image. Each time you call it up and save it again, it
    re-evaluates the colors and makes more compressions - thus
    degrading the image. How much compression it performs
    depends on the "quality" setting when you invoke the
    compression. If you set the value high, you can save multiple
    times with hardly any perceptible change. If you set it low,
    the difference will be perceptible on the very first save.

    I suggest you do this:

    Get a high quality image, e.g., straight from your camera.
    Save it as a new image, with a new name, e.g., image1.
    Call it up again and save again as image2, and again and

    Do this once with a high setting and once with a lower

    Then look at the images carefully and compare them.

    It will tell you more about what's acceptable to you than
    any amount of advice from experts.

    For me, I use software that saves images with quality
    settings from 1-9. At 9, I get an average of about 10:1
    compression from the original uncompressed size. Saving
    at 9 again makes it a bit smaller, but not much. With my
    software and my own personal preferences, I find that
    saving it several times is not a problem.

    Alan Meyer, Aug 17, 2004
  9. John Tomasi

    Alan Meyer Guest


    You're right, but I'm not sure that's what John did.
    If what he did was save the modified image over
    the original, obliterating the original, then he has
    permanently lost some information unless he's
    got another copy of the original file stashed away

    Also, I'm not sure he's using Photoshop.

    Alan Meyer, Aug 17, 2004
  10. John Tomasi

    Ron Hunter Guest

    First, it is the process of recompressing the JPEG picture that loses
    data. Saving it just saves that recompressed, changed, picture. If you
    return to the original image data, saved by the software, and then save,
    a well-written program will NOT resave the data, so no further data loss
    would take place.
    Unless we are talking about several (say 6 or more) saves, loads, edits,
    and saves, then you probably won't seen any noticeable change in the image.
    Ron Hunter, Aug 17, 2004
  11. John Tomasi

    John Tomasi Guest

    Wow! You guys are an amazing source of information. From everything
    you've said, I think I may be all right. I'm using Photoshop, and in my
    save settings the image quality is set to high (12 on the slider).

    Can you further advise me, when saving JPEGS, whether to save as
    "standardized" or "optimized"?
    John Tomasi, Aug 17, 2004
  12. John Tomasi

    Jeremy Nixon Guest

    I've never seen any difference in practice between the two in terms of
    compatibility with other software (which would be the difference).
    Jeremy Nixon, Aug 17, 2004
  13. John Tomasi

    Rob Graham Guest


    I had an interesting experience from which I learnt the lesson of not
    re-saving jpg's.

    I was using IrfanView to do some basic messing about and did a re-save - the
    picture seemd fine but for some reason I can't remember I set it to some
    huge zoom factor and discovered that the sky looked like the colours were
    running like a over-wet water painting. Fortunately there was a guru at
    hand to explain. But it was a good example of what happens when re-saving
    using the default setting of compression. It might have been worthwhile
    experimenting with the compression factor set to minimum but I never did.

    What I do now is to save all processed pictures as tiff files as the
    compression is not lossy. Ok they are then about the size of a RAW file
    (10MB) but storage is cheap and there is no further loss in quality.


    Rob Graham, Aug 18, 2004
  14. John Tomasi

    Hunt Guest

    In PS (if you have not left the image, i.e. Crtl-w, or Close), just go to
    History Palette and go back to Open, provided that you have not exceeded your
    setting for History "states." I assume that by now, you have already closed
    the file, the program, and probably re-started your computer. If so, the
    answer is no. Two things to possibly help in the future would be 1.) never
    work on an original file, which has not been backed up someplace else. 2.) use
    the Snapshot feature in PS (other programs probably have them too), before you
    do any Save act. Unfortunately, Save and Save_As are too close for comfort.
    Even with keyboard shortcuts, if the Shift key is not fully depressed on PS's
    Ctrl-Shift-S, you get Save! For any critical images, I make a habit of loading
    to computer, burning CD, copying files to "work" folder, doing any
    manipulations, and then Save_As in yet another folder. Redundant - yes. Worth
    it? - yes. It's saved me many, many times over. I'll also save each variation
    that is getting close to what I want as PSD, every step of the way. Lots of
    HDD space and a ton of CD-R's is the only way to go. I then add DAT bu of ALL
    images and their variations.

    Hunt, Aug 18, 2004
  15. John Tomasi

    Hunt Guest

    Correct, and I should have added to always Save_As .PSD if in Photoshop, until
    you have the image as you intend, then, and only then, Save in JPG. Don't
    throw away those PSD's, until you are absolutely certain that you will NEVER
    EVER go back to them.

    Hunt, Aug 18, 2004
  16. John Tomasi

    Arty Facting Guest

    Yep - to the big wide wurld that is ciderspace and beyond I'd like to eko
    Hunt's statement

    Never mix WIP with original images (WIP = work in progress)

    ask any data analyst or statistician why and, after all, images are forms of
    data too

    FWIW my 0.02c is
    1 - prime image folders contain images straight from the digicam or source

    2 - transfer a copy of image from Prime folder to WIP folder

    3 - never, ever mix the 2 up even when you are in a huge rush - that usually
    is when the critical mistake is made

    I know it is probably poor consolation but it is something we all do from


    ps - don't let me tell you the story of the person preferring to format
    floppies by DOS commands rather than by Windows commands

    Of course the person was very experienced and probably still is but or
    rather B-U-T in a millesecond of distraction instead of formatting A: it was
    C: that got the reformat. Well you can gues can't you? A major walk around
    the block but I will save that story for another time


    Arty Facting, Aug 18, 2004
  17. John Tomasi

    Arty Facting Guest

    drat! re-read me post! tsk story has gone ....

    anyway as a good mnemo pmemo, erm mnemo - erm aide memoir think:

    WIP to do, whipped if you don't!


    Arty Facting, Aug 18, 2004
  18. John Tomasi

    Martin Brown Guest

    The trick is to treat your original ex-camera images like you would the
    original film negatives. You make no modifications to them - treat as
    read only. On some systems you can even enforce this at an OS level.
    That is a case for setting a more acceptable (to you) default
    compression level. Optimum settings for resaving a JPEG are typically
    obtained when the quality is a close match for that of the original
    PNG is also lossless compression and often quite a bit smaller than
    TIFF. For work in progress it is usually better to store in the
    applications native format that supports layers and other app specific

    Martin Brown, Aug 19, 2004
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