JPEG and lossy

Discussion in 'Digital Photography' started by Conrad, Jul 20, 2006.

  1. Conrad

    Conrad Guest

    Hi,

    Working with JPEG files - does opening and closing cause lossy damage
    to image or do you have to perform tweaks (i.e., within Photoshop) to
    cause any potential loss of quality?


    TIA,

    Conrad
    Camp Sherman, Oregon
    Conrad, Jul 20, 2006
    #1
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  2. Conrad

    Joe Makowiec Guest

    On 20 Jul 2006 in rec.photo.digital, Conrad wrote:

    > Working with JPEG files - does opening and closing cause lossy damage
    > to image or do you have to perform tweaks (i.e., within Photoshop) to
    > cause any potential loss of quality?


    No. Only edits/resaves.

    --
    Joe Makowiec
    http://makowiec.org/
    Email: http://makowiec.org/contact/?Joe
    Joe Makowiec, Jul 20, 2006
    #2
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  3. Conrad

    POHB Guest

    Conrad wrote:
    > Hi,
    >
    > Working with JPEG files - does opening and closing cause lossy damage
    > to image or do you have to perform tweaks (i.e., within Photoshop) to
    > cause any potential loss of quality?


    Opening and viewing a file won't change it. Tweaking the file once it
    is open still won't affect the original file until you hit Save. It is
    only if you save changes and overwrite the original file that you can
    affect the quality of that file. If you save your tweaks to a new
    filename then your original is still available at its original quality.
    If you want to make multiple tweaks across different editing sessions
    then save the intermediate results in a lossless format.
    POHB, Jul 20, 2006
    #3
  4. Conrad

    Guest

    POHB wrote:
    snip

    > If you want to make multiple tweaks across different editing sessions
    > then save the intermediate results in a lossless format.


    Further, in that case, save it in the native file format of your editor
    (PS for Photoshop, PSP for Paint Shop Pro, etc.). If you save it to
    some other format, you are likey to LOSE some of the editing
    information in the editing you have been doing. For instance, if you
    have created layers, and are working on them, most standard formats
    will NOT save the layer info.

    When editing, always save at end of session in the native format, and
    do not convert to a standard format until you are SURE you are done
    editing.
    , Jul 20, 2006
    #4
  5. Conrad

    Ed Ruf Guest

    On Thu, 20 Jul 2006 12:03:42 GMT, in rec.photo.digital Joe Makowiec
    <> wrote:

    >On 20 Jul 2006 in rec.photo.digital, Conrad wrote:
    >
    >> Working with JPEG files - does opening and closing cause lossy damage
    >> to image or do you have to perform tweaks (i.e., within Photoshop) to
    >> cause any potential loss of quality?

    >
    >No. Only edits/resaves.


    Actually, one need not even edit. It is strictly the saving where the
    compression is applied. If you repeatedly open and resave a jpg, very
    quickly the loss in quality will be come readily apparent.
    ________________________________________________________
    Ed Ruf Lifetime AMA# 344007 ()
    http://EdwardGRuf.com
    Ed Ruf, Jul 20, 2006
    #5
  6. On 7/20/06 7:31 AM, Ed Ruf wrote:
    > On Thu, 20 Jul 2006 12:03:42 GMT, in rec.photo.digital Joe Makowiec
    > <> wrote:
    >
    >> On 20 Jul 2006 in rec.photo.digital, Conrad wrote:
    >>
    >>> Working with JPEG files - does opening and closing cause lossy damage
    >>> to image or do you have to perform tweaks (i.e., within Photoshop) to
    >>> cause any potential loss of quality?

    >> No. Only edits/resaves.

    >
    > Actually, one need not even edit. It is strictly the saving where the
    > compression is applied. If you repeatedly open and resave a jpg, very
    > quickly the loss in quality will be come readily apparent.


    If you open a jpeg in a competent graphics program, and do not edit,
    there is no re-compression, and hence no loss. Programs that do
    otherwise are rather lacking.

    And, Ed, if you'd kindly place a sig delimiter before your tag lines,
    it'd be appreciated.

    --
    john mcwilliams
    John McWilliams, Jul 20, 2006
    #6
  7. Conrad

    Bill Funk Guest

    On Thu, 20 Jul 2006 08:11:54 -0700, John McWilliams
    <> wrote:

    >If you open a jpeg in a competent graphics program, and do not edit,
    >there is no re-compression, and hence no loss. Programs that do
    >otherwise are rather lacking.


    As was said before, it's not the editing that causes loss, it's the
    saving.
    Open and edit a Jpeg file all you want. If you don't save it, there's
    no action performed on the opened file.
    Are there actually apps being marketed that will automatically save
    any opened files without action on the part of the user?
    --
    Bill Funk
    replace "g" with "a"
    Bill Funk, Jul 20, 2006
    #7
  8. Conrad

    Hebee Jeebes Guest

    If you just open and close them and don't do anything to them or perform a
    save command then it doesn't degrade. If Photoshop asks you to save when you
    close then you made changes and this would cause additional image loss if
    you saved it in JPG. I convert my JPGs to TIFs when I work on them so that I
    don't have to worry about the JPG lossy business.

    R


    "Conrad" <> wrote in message
    news:...
    > Hi,
    >
    > Working with JPEG files - does opening and closing cause lossy damage
    > to image or do you have to perform tweaks (i.e., within Photoshop) to
    > cause any potential loss of quality?
    >
    >
    > TIA,
    >
    > Conrad
    > Camp Sherman, Oregon
    >
    Hebee Jeebes, Jul 20, 2006
    #8
  9. On 7/20/06 10:10 AM, Bill Funk wrote:
    > On Thu, 20 Jul 2006 08:11:54 -0700, John McWilliams
    > <> wrote:
    >
    >> If you open a jpeg in a competent graphics program, and do not edit,
    >> there is no re-compression, and hence no loss. Programs that do
    >> otherwise are rather lacking.

    >
    > As was said before, it's not the editing that causes loss, it's the
    > saving.


    Of course. But someone seems to think that just saving an open jpeg will
    cause losses, which it won't with a competent image app.

    > Open and edit a Jpeg file all you want. If you don't save it, there's
    > no action performed on the opened file.


    Of course. [see above].
    > Are there actually apps being marketed that will automatically save
    > any opened files without action on the part of the user?


    Not that I am aware of on the Mac platform. Some allow autosave, but
    they're not image apps. and you have to set same in Prefs.

    Of course, all the above fairly begs the question as to what "saving"
    actually means.

    --
    john mcwilliams
    John McWilliams, Jul 20, 2006
    #9
  10. Conrad

    Ed Ruf Guest

    On Thu, 20 Jul 2006 12:37:13 -0700, in rec.photo.digital John
    McWilliams <> wrote:

    >Of course. But someone seems to think that just saving an open jpeg will
    >cause losses, which it won't with a competent image app.


    Open a file in PS CS2, choose Save As to another name. Guess what, it
    recompresses. Open a file in PSP7 or 8 (as the versions I have) just
    click Save. Guess what?
    ________________________________________________________
    Ed Ruf Lifetime AMA# 344007 ()
    http://EdwardGRuf.com
    Ed Ruf, Jul 20, 2006
    #10
  11. Conrad

    KarstenSc Guest

    On Thu, 20 Jul 2006 10:10:47 -0700, Bill Funk <>
    wrote:

    >On Thu, 20 Jul 2006 08:11:54 -0700, John McWilliams
    ><> wrote:
    >
    >>If you open a jpeg in a competent graphics program, and do not edit,
    >>there is no re-compression, and hence no loss. Programs that do
    >>otherwise are rather lacking.

    >
    >As was said before, it's not the editing that causes loss, it's the
    >saving.
    >Open and edit a Jpeg file all you want. If you don't save it, there's
    >no action performed on the opened file.


    Well, in fact you can even edit some informations, without any need to
    re-compress the image information itself.
    If you only want to changeMeta Informations like Exif, change an ICC
    profile or modify Photoshop Blocks like Working Paths, a capable
    program should be able to save the modified image without any
    re-compression for the image data itself.
    KarstenSc, Jul 20, 2006
    #11
  12. On 7/20/06 1:47 PM, Ed Ruf wrote:
    > On Thu, 20 Jul 2006 12:37:13 -0700, in rec.photo.digital John
    > McWilliams <> wrote:
    >
    >> Of course. But someone seems to think that just saving an open jpeg will
    >> cause losses, which it won't with a competent image app.

    >
    > Open a file in PS CS2, choose Save As to another name. Guess what, it
    > recompresses. Open a file in PSP7 or 8 (as the versions I have) just
    > click Save. Guess what?
    >

    No guessing required. Save As in PS is different from Save. If one
    wishes an exact copy of an image, one uses a Finder copy.

    Your sig delimiter is still missing.

    --
    john mcwilliams
    John McWilliams, Jul 20, 2006
    #12
  13. Ed Ruf (REPLY to E-MAIL IN SIG!), Jul 20, 2006
    #13
  14. On 7/20/06 3:27 PM, Ed Ruf (REPLY to E-MAIL IN SIG!) wrote:
    > On Thu, 20 Jul 2006 14:45:32 -0700, in rec.photo.digital John McWilliams
    > <> wrote:
    >
    >
    >> Your sig delimiter is still missing.

    >
    > If it bothers you some much fix it yourself.
    > --
    > Ed Ruf ()
    > http://edwardgruf.com/Digital_Photography/General/index.html


    If you now put a space behind the two dashes, you'll have it nailed!

    --
    john mcwilliams
    John McWilliams, Jul 20, 2006
    #14
  15. On Thu, 20 Jul 2006 15:31:24 -0700, in rec.photo.digital John McWilliams
    <> wrote:

    >On 7/20/06 3:27 PM, Ed Ruf (REPLY to E-MAIL IN SIG!) wrote:
    >> On Thu, 20 Jul 2006 14:45:32 -0700, in rec.photo.digital John McWilliams
    >> <> wrote:
    >>
    >>
    >>> Your sig delimiter is still missing.

    >>
    >> If it bothers you some much fix it yourself.
    >> --
    >> Ed Ruf ()
    >> http://edwardgruf.com/Digital_Photography/General/index.html

    >
    >If you now put a space behind the two dashes, you'll have it nailed!


    You did not get it. Given the implied attitude in your second mention of
    it, right now as far as I'm concerned hell could freeze over first.
    --
    Ed Ruf ()
    http://edwardgruf.com/Digital_Photography/General/index.html
    Ed Ruf (REPLY to E-MAIL IN SIG!), Jul 21, 2006
    #15
  16. "Ed Ruf (REPLY to E-MAIL IN SIG!)" <> wrote:
    >>
    >>If you now put a space behind the two dashes, you'll have it nailed!

    >
    >You did not get it. Given the implied attitude in your second mention of
    >it, right now as far as I'm concerned hell could freeze over first.
    >--
    >Ed Ruf ()
    >http://edwardgruf.com/Digital_Photography/General/index.html


    Why not set your ego aside... and post correctly constructed
    articles. It won't make him any more right or wrong, but at
    least your articles won't be wrong every single time!

    --
    Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
    Ukpeagvik (Barrow, Alaska)
    Floyd L. Davidson, Jul 21, 2006
    #16
  17. Conrad wrote:
    > Hi,
    >
    > Working with JPEG files - does opening and closing cause lossy damage
    > to image or do you have to perform tweaks (i.e., within Photoshop) to
    > cause any potential loss of quality?
    >
    >
    > TIA,
    >
    > Conrad
    > Camp Sherman, Oregon
    >

    Try using Picasa2. No matter what you do to your image, Picasa2 retains
    the original image. All tweaks can be cancelled easily, returning you to
    your original image with no loss.
    Morton
    --
    Morton Linder, Jul 21, 2006
    #17
  18. On 7/20/06 5:12 PM, Ed Ruf (REPLY to E-MAIL IN SIG!) wrote:
    > On Thu, 20 Jul 2006 15:31:24 -0700, in rec.photo.digital John McWilliams
    > <> wrote:
    >
    >> On 7/20/06 3:27 PM, Ed Ruf (REPLY to E-MAIL IN SIG!) wrote:
    >>> On Thu, 20 Jul 2006 14:45:32 -0700, in rec.photo.digital John McWilliams
    >>> <> wrote:
    >>>
    >>>
    >>>> Your sig delimiter is still missing.


    >> If you now put a space behind the two dashes, you'll have it nailed!

    >
    > You did not get it. Given the implied attitude in your second mention of
    > it, right now as far as I'm concerned hell could freeze over first.


    Of course, Ed, I am not a rocket scientist, but I swear most folks are
    able to correct a sig delimiter without getting in a swivet.

    YMMV, and, I know now, does.

    --
    john mcwilliams
    John McWilliams, Jul 21, 2006
    #18
  19. Conrad

    Keith Guest

    Morton Linder <> wrote:

    > Conrad wrote:
    > > Hi,
    > >
    > > Working with JPEG files - does opening and closing cause lossy damage
    > > to image or do you have to perform tweaks (i.e., within Photoshop) to
    > > cause any potential loss of quality?
    > >
    > >
    > > TIA,
    > >
    > > Conrad
    > > Camp Sherman, Oregon
    > >

    > Try using Picasa2. No matter what you do to your image, Picasa2 retains
    > the original image. All tweaks can be cancelled easily, returning you to
    > your original image with no loss.
    > Morton
    > --


    iPhoto does the same kind of thing ( as well as Aperture ) It keeps the
    original and you can tweak the image to your hearts content. If you
    don't like the changes/edits you can revert to the original and start
    again anytime.
    Keith, Jul 21, 2006
    #19
  20. Conrad

    Ron Hunter Guest

    Ed Ruf wrote:
    > On Thu, 20 Jul 2006 12:03:42 GMT, in rec.photo.digital Joe Makowiec
    > <> wrote:
    >
    >> On 20 Jul 2006 in rec.photo.digital, Conrad wrote:
    >>
    >>> Working with JPEG files - does opening and closing cause lossy damage
    >>> to image or do you have to perform tweaks (i.e., within Photoshop) to
    >>> cause any potential loss of quality?

    >> No. Only edits/resaves.

    >
    > Actually, one need not even edit. It is strictly the saving where the
    > compression is applied. If you repeatedly open and resave a jpg, very
    > quickly the loss in quality will be come readily apparent.
    > ________________________________________________________
    > Ed Ruf Lifetime AMA# 344007 ()
    > http://EdwardGRuf.com


    Nope, not unless your program is written by a total boob. No software I
    am aware of recompresses an image to save if it hasn't been edited. If
    you have such software, I suggest you get something worth loading into
    your ram.
    Ron Hunter, Jul 21, 2006
    #20
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