Quality loss on saving

Discussion in 'Digital Photography' started by John Lee, May 28, 2004.

  1. John Lee

    John Lee Guest

    I understand that every time a JPEG image is saved (after modification of
    any sort) there is an inevitable small loss of quality. However, does anyone
    know whether there is any loss if a 'layer' is added to an image? For
    example, I often use PaintShop Pro to add captions to an image.

    Thanks for any comments.

    John
    John Lee, May 28, 2004
    #1
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  2. John Lee

    Paul Howland Guest

    John Lee wrote:
    > I understand that every time a JPEG image is saved (after modification of
    > any sort) there is an inevitable small loss of quality. However, does anyone
    > know whether there is any loss if a 'layer' is added to an image? For
    > example, I often use PaintShop Pro to add captions to an image.
    >
    > Thanks for any comments.
    >
    > John


    If you save it as JPEG, yes. Everytime the image is changed it must be
    recompressed.
    Paul Howland, May 28, 2004
    #2
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  3. John Lee

    Bob Hatch Guest

    "John Lee" <> wrote in message
    news:8iLtc.83$
    > I understand that every time a JPEG image is saved (after
    > modification of any sort) there is an inevitable small loss of
    > quality. However, does anyone know whether there is any loss if a
    > 'layer' is added to an image? For example, I often use PaintShop Pro
    > to add captions to an image.
    >

    Yes there is a loss, but if saved at the highest quality you won't be able
    to see the difference.

    Try this. Open an image, Add a caption then save the image as one.jpg. Close
    it, reopen, add another caption and save it as two.jpg. Do that 10 times.
    Print image one, five and ten and lay them on a table side by side and see
    how small the difference is between one and ten. Notice I'm not suggesting
    there is no difference, it's just vary small at the printed resolution. Also
    the images must be saved at best quality.
    --
    "Your money does not cause my poverty. Refusal to believe
    this is at the bottom of most bad economic thinking." --P. J. O'Rourke
    http://www.bobhatch.com
    Bob Hatch, May 28, 2004
    #3
  4. John Lee

    Brad Guest

    In article <8iLtc.83$>,
    said...
    > I understand that every time a JPEG image is saved (after modification of
    > any sort) there is an inevitable small loss of quality. However, does anyone
    > know whether there is any loss if a 'layer' is added to an image? For
    > example, I often use PaintShop Pro to add captions to an image.
    >
    > Thanks for any comments.


    JPG doesn't have layers, so adding text and saving is no different that
    editing any other way. The whole thing is still re-saved.
    Brad, May 28, 2004
    #4
  5. In article <40b77352$0$1731$>, Paul Howland
    <> writes
    >John Lee wrote:
    >> I understand that every time a JPEG image is saved (after modification of
    >> any sort) there is an inevitable small loss of quality. However, does anyone
    >> know whether there is any loss if a 'layer' is added to an image? For
    >> example, I often use PaintShop Pro to add captions to an image.
    >> Thanks for any comments.
    >> John

    >
    >If you save it as JPEG, yes. Everytime the image is changed it must be
    >recompressed.


    IIRC, this is also true if you save it without any modification at all;
    the very act of "saving" re-computes the compression algorithm. The only
    way to avoid degradation is to close the file without saving (assuming,
    of course, that you have not modified it or don't want to keep the
    modifications).

    IMO, it is always a good idea to work only on a copy of the original
    jpeg (if you only have the jpeg of course) and leave the original
    untouched.
    --
    David Littlewood
    David Littlewood, May 28, 2004
    #5
  6. John Lee

    leo Guest

    "John Lee" <> wrote in message
    news:8iLtc.83$...
    > I understand that every time a JPEG image is saved (after modification of
    > any sort) there is an inevitable small loss of quality. However, does

    anyone
    > know whether there is any loss if a 'layer' is added to an image? For
    > example, I often use PaintShop Pro to add captions to an image.
    >
    > Thanks for any comments.
    >
    > John



    I don't think there'll be much changes in picture quality if it's saved
    using maximum quality. However, I do notice that if I save the original
    picture (RAW -> TIFF) in plain jpeg (sRGB), the color is very dull. If I
    save with ICC included (Adobe RGB), the color is the same as what I see in
    Photoshop, more vivid.
    leo, May 28, 2004
    #6
  7. John Lee

    Ed Ruf Guest

    On Fri, 28 May 2004 18:12:33 +0100, in rec.photo.digital "John Lee"
    <> wrote:

    >I understand that every time a JPEG image is saved (after modification of
    >any sort) there is an inevitable small loss of quality. However, does anyone
    >know whether there is any loss if a 'layer' is added to an image? For
    >example, I often use PaintShop Pro to add captions to an image.


    If you then save this to jpg the image will first be "flattened" as jpg
    does not support layers then recompressed as it is saved. This is why after
    saving you can never edit the caption. If you think you might want to edit
    the image again better to save it to PSP's native format.
    ________________________________________________________
    Ed Ruf Lifetime AMA# 344007 ()
    See images taken with my CP-990 and 5700 at
    http://EdwardGRuf.com
    Ed Ruf, May 28, 2004
    #7
  8. John Lee

    Alex Butcher Guest

    On Fri, 28 May 2004 20:17:35 +0100, David Littlewood wrote:

    > In article <40b77352$0$1731$>, Paul Howland
    > <> writes
    >>John Lee wrote:
    >>> I understand that every time a JPEG image is saved (after modification of
    >>> any sort) there is an inevitable small loss of quality. However, does anyone
    >>> know whether there is any loss if a 'layer' is added to an image? For
    >>> example, I often use PaintShop Pro to add captions to an image.
    >>> Thanks for any comments.
    >>> John

    >>
    >>If you save it as JPEG, yes. Everytime the image is changed it must be
    >>recompressed.

    >
    > IIRC, this is also true if you save it without any modification at all;
    > the very act of "saving" re-computes the compression algorithm. The only
    > way to avoid degradation is to close the file without saving (assuming,
    > of course, that you have not modified it or don't want to keep the
    > modifications).


    ....or convert the JPEG to a non-lossy format (e.g. TIFF or PNG), and work
    on /that/ saving as and when you wish. When you've finished editing, you
    can convert the final image back to JPEG at the expense of a little loss
    of quality (but still MUCH less than would be incurred by repeated
    re-compression and re-saving of the original JPEG).

    Better still, if you're taking a photo you know you're going to
    extensively post-process, take it in your camera's TIFF or CCDRAW mode
    (assuming it has one).

    Best Regards,
    Alex.
    --
    Alex Butcher Brainbench MVP for Internet Security: www.brainbench.com
    Bristol, UK Need reliable and secure network systems?
    PGP/GnuPG ID:0x271fd950 <http://www.assursys.com/>
    Alex Butcher, May 28, 2004
    #8
  9. John Lee

    Steven Wandy Guest

    > IIRC, this is also true if you save it without any modification at all;

    Not if you just open and close the image. What would be the purpose of
    "saving" if you did not make any changes to the image?
    Steven Wandy, May 29, 2004
    #9
  10. In article <Eb0uc.150393$>, Steven Wandy
    <> writes
    >> IIRC, this is also true if you save it without any modification at all;

    >
    >Not if you just open and close the image. What would be the purpose of
    >"saving" if you did not make any changes to the image?
    >
    >

    That is exactly what I said. However, as to why someone might do it,
    there is the possibility of ignorance or inadvertence.
    --
    David Littlewood
    David Littlewood, May 29, 2004
    #10
  11. John Lee

    Don Stauffer Guest

    As long as you are working on it, save it as .psp. When you are
    complete with editing, then you may resave once with JPEG. Note that
    when you try to save the image as .jpg, the program will inform you that
    you will lose some formatting (particularly seperate layers in this
    case. So keep it in .psp for as long as you think you might be doing
    things to image.

    John Lee wrote:
    >
    > I understand that every time a JPEG image is saved (after modification of
    > any sort) there is an inevitable small loss of quality. However, does anyone
    > know whether there is any loss if a 'layer' is added to an image? For
    > example, I often use PaintShop Pro to add captions to an image.
    >
    > Thanks for any comments.
    >
    > John


    --
    Don Stauffer in Minnesota

    webpage- http://www.usfamily.net/web/stauffer
    Don Stauffer, May 29, 2004
    #11
  12. John Lee

    Ed Ruf Guest

    On Sat, 29 May 2004 09:37:55 -0500, in rec.photo.digital Don Stauffer
    <> wrote:

    >As long as you are working on it, save it as .psp. When you are
    >complete with editing, then you may resave once with JPEG. Note that
    >when you try to save the image as .jpg, the program will inform you that
    >you will lose some formatting (particularly seperate layers in this
    >case.


    FWIW, in at least PSP8 this depends upon how you've set the File Format
    Limitations preference in File => Preferences => General Program
    Preferences => Warnings.
    ________________________________________________________
    Ed Ruf Lifetime AMA# 344007 ()
    See images taken with my CP-990 and 5700 at
    http://EdwardGRuf.com
    Ed Ruf, May 29, 2004
    #12
  13. John Lee

    Guest

    John Lee <> wrote:
    > I understand that every time a JPEG image is saved (after modification of
    > any sort) there is an inevitable small loss of quality. However, does anyone
    > know whether there is any loss if a 'layer' is added to an image? For
    > example, I often use PaintShop Pro to add captions to an image.


    Your question does not make sense. Image files in jpg format do not
    support layers so there is no way to do what you propose. Once you
    use PaintShop Pro to add captions to an image, the only way to save
    the modified image in jpg is to flatten the image so that its layers
    are lost. If you than take that flattened jpg image and save it again
    as a jpg, and do it again and again, you will lose detail after each
    save. If you keep that image in the native format that PaintShop Pro
    uses, then your images shouldn't experience any degredation in quality.
    , May 29, 2004
    #13
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