Wall Street Journal - technology report on digital cameras

Discussion in 'Digital Photography' started by nospam650@yahoo.com, May 26, 2005.

  1. Guest

    part of the WSJ technology article at

    http://ptech.wsj.com/ptech.html


    "there's a difference in quality over time between JPEG -- which is
    known as a "lossy" format because it discards, and thus loses, some
    data each time an image is opened on your computer and then
    recompressed as it is closed -- and formats like TIFF (for Tagged Image
    File Format) and RAW (as in unprocessed), which preserve all the image
    data. As debates rage about which shooting format is best (RAW is hot
    now among chatterers at Web photo sites), a handful of guidelines has
    emerged."


    is this true -- with the jpg format the actual file on the computer
    changes each time you view it?
    , May 26, 2005
    #1
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  2. Guest

    >JPEG -- which is known as a "lossy" format because it discards,
    >and thus loses, some data each time an image is opened


    NO. Jpeg files do NOT lose any data when opened.

    >..and then recompressed as it is closed


    NO again. Jpeg files ONLY lose data when they are SAVED. And even
    then, significant extra losses generally only occur in areas that are
    edited/cropped, and when the compression ratio is changed (although it
    depends somewhat on the software)..

    Opening and closing JPEG files, without re-saving, has absolutely no
    effect on the file, and the author of that article should not be
    allowed near a digital editor, computer or camera...

    (That doesn't mean that Jpeg files *should* be used as an archiving
    format, but it would be nice if they got their facts right.)
    , May 26, 2005
    #2
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  3. Dave Guest

    <> wrote
    > >JPEG -- which is known as a "lossy" format because it discards,
    > >and thus loses, some data each time an image is opened

    >
    > NO. Jpeg files do NOT lose any data when opened.
    >
    > >..and then recompressed as it is closed

    >
    > NO again. Jpeg files ONLY lose data when they are SAVED. And even
    > then, significant extra losses generally only occur in areas that are
    > edited/cropped, and when the compression ratio is changed (although it
    > depends somewhat on the software)..
    >
    > Opening and closing JPEG files, without re-saving, has absolutely no
    > effect on the file, and the author of that article should not be
    > allowed near a digital editor, computer or camera...
    >
    > (That doesn't mean that Jpeg files *should* be used as an archiving
    > format, but it would be nice if they got their facts right.)


    OK, I thought that didn't sound right. I suppose it's like MP3's - you
    can play them but don't expand to a "wav" file and save! makes you
    wonder about the accuracy of the rest of the article.
    thanks
    Dave, May 26, 2005
    #3
  4. writes:

    > part of the WSJ technology article at
    >
    > http://ptech.wsj.com/ptech.html
    >
    >
    > "there's a difference in quality over time between JPEG -- which is
    > known as a "lossy" format because it discards, and thus loses, some
    > data each time an image is opened on your computer and then
    > recompressed as it is closed -- and formats like TIFF (for Tagged Image
    > File Format) and RAW (as in unprocessed), which preserve all the image
    > data. As debates rage about which shooting format is best (RAW is hot
    > now among chatterers at Web photo sites), a handful of guidelines has
    > emerged."
    >
    >
    > is this true -- with the jpg format the actual file on the computer
    > changes each time you view it?


    No the key part of the sentence is "recompressed as it is closed". Ie, if you
    have a JPEG file, open it up in an editor, change something, and resave it, the
    act of resaving it will add to the loss. Just viewing the file without
    resaving it will not change the bits. Some people will save intermediate edits
    in a lossless format (such as TIFF, PNG, or the internal format of photoshop)
    to prevent a gradual accumulation of errors. I generally shoot at the least
    amount of compression in my cameras, only edit the file in one session, and
    then save it, and it is good enough for my purposes.

    --
    Michael Meissner
    email:
    http://www.the-meissners.org
    Michael Meissner, May 26, 2005
    #4
  5. On 25 May 2005 18:55:17 -0700, in rec.photo.digital ,
    in
    <> wrote:

    >part of the WSJ technology article at
    >
    >http://ptech.wsj.com/ptech.html
    >
    >
    >"there's a difference in quality over time between JPEG -- which is
    >known as a "lossy" format because it discards, and thus loses, some
    >data each time an image is opened on your computer and then
    >recompressed as it is closed -- and formats like TIFF (for Tagged Image
    >File Format) and RAW (as in unprocessed), which preserve all the image
    >data. As debates rage about which shooting format is best (RAW is hot
    >now among chatterers at Web photo sites), a handful of guidelines has
    >emerged."
    >
    >
    >is this true -- with the jpg format the actual file on the computer
    >changes each time you view it?


    No.


    --
    Matt Silberstein

    All in all, if I could be any animal, I would want to be
    a duck or a goose. They can fly, walk, and swim. Plus,
    there there is a certain satisfaction knowing that at the
    end of your life you will taste good with an orange sauce
    or, in the case of a goose, a chestnut stuffing.
    Matt Silberstein, May 26, 2005
    #5
  6. ASAAR Guest

    On 25 May 2005 19:06:43 -0700, wrote:

    > Opening and closing JPEG files, without re-saving, has absolutely
    > no effect on the file, and the author of that article should not be
    > allowed near a digital editor, computer or camera...


    But it's true. In some of the offices of the Wall Street Journal,
    JPG files do degrade when viewed. The VIPs in the editorial section
    aren't technically savvy, and prefer using the technology available
    during the Cold War Era. They use lovingly preserved analog
    computers which retrieve the JPG files from vinyl disk jukebox
    drives. Until they're too worn due scratches and other surface
    noise, the JPGs have a wonderously warm appearance that can't be
    matched by the cold, harsh images displayed by digital computers.

    The author appears to have the qualifications necessary to write
    for the WSJ's editorial section, needing perhaps only a secretary to
    type the text and read him or her the day's talking points.
    ASAAR, May 26, 2005
    #6
  7. ASAAR Guest

    On 25 May 2005 22:55:25 -0400, Michael Meissner wrote:

    >> there's a difference in quality over time between JPEG -- which is
    >> known as a "lossy" format because it discards, and thus loses, some
    >> data each time an image is opened on your computer and then
    >> recompressed as it is closed


    > No the key part of the sentence is "recompressed as it is closed". Ie, if you
    > have a JPEG file, open it up in an editor, change something, and resave it, the
    > act of resaving it will add to the loss. Just viewing the file without
    > resaving it will not change the bits.


    No, you're mistaken. Note what precedes "recompressed as it is
    closed". It says that the loss occurs *each time* the image is
    opened and then closed. Whether it's an editing app. or a viewing
    app. that can't make any changes to the file, they both "open" the
    JPG files. When they're finished with the JPG, the files are always
    "closed" by both apps. Gotta do it. Files might not be explicitly
    closed by the app. if it's buggy or if it crashes, but that's
    something else. The act of "closing" a file does not indicate that
    anything will necessarily be written to the disk. The only changes
    made to the disk if nothing was saved might be the "last accessed
    date/time", but that's not part of the JPG file itself, and if files
    aren't closed by the viewing app. it can lead to what's known as
    "memory leak". If the author knew as much as you, he/she would have
    said "each time an image is opened, modified and saved on your
    computer, it will lose a little more detail due to JPG's lossy
    compression." Note that many editing programs are smart enough to
    ignore requests to "save" files if the files haven't actually been
    edited or modified by the user. But they always eventually "close"
    the files.
    ASAAR, May 26, 2005
    #7
  8. Paul J Gans Guest

    wrote:
    >part of the WSJ technology article at


    >http://ptech.wsj.com/ptech.html



    >"there's a difference in quality over time between JPEG -- which is
    >known as a "lossy" format because it discards, and thus loses, some
    >data each time an image is opened on your computer and then
    >recompressed as it is closed -- and formats like TIFF (for Tagged Image
    >File Format) and RAW (as in unprocessed), which preserve all the image
    >data. As debates rage about which shooting format is best (RAW is hot
    >now among chatterers at Web photo sites), a handful of guidelines has
    >emerged."



    >is this true -- with the jpg format the actual file on the computer
    >changes each time you view it?


    No. Only if you save it again. And why would you do that?
    After all, you are just looking at it.

    On the other hand if you manipulate your jpegs in any way, it
    is wise to convert the jpeg to a lossless format such as TIFF
    right away. This takes up more disk space but you can save
    an unchanged TIFF over and over again without losing anything.

    ---- Paul J. Gans
    Paul J Gans, May 26, 2005
    #8
  9. Guest

    > makes you wonder about the accuracy of the rest of the article

    Indeed, but the quick skim I did indicated there wasn't much else wrong
    with the logic. But that bit of misinformation is not really
    forgivable - if he knows so little about jpg files, he clearly is not
    an expert on the topic.

    Oh, and and as for those vinylly recorded jpegs, all they need do is to
    play them back on a valve-based computer, to get the benefit of that
    rich analogue warmness! Then, even the jpeg artefacts look wonderful!
    I beleive Leica may make just such a computer for their new range of
    hybrid anadigicams.
    , May 26, 2005
    #9
  10. In article <>,
    says...

    > is this true -- with the jpg format the actual file on the computer
    > changes each time you view it?


    No, it's only true if the statement is taken as a whole -- there's
    additional loss when the file is "recompressed as it is closed." If
    you just view a file, you shouldn't be making a new, recompressed
    version of it. You should just stop viewing the existing version of
    it without saving a new version.

    Now, I have known some people who used editors for viewing and had
    the habit of doing a "save-and-exit" instead of just an "exit" when
    they were done viewing, and in that case, yes, they'd be
    recompressing the file every time they viewed it, and that could
    produce additional losses.

    While it's technically correct, the wording of the article is far
    from clear, because it is open to exactly the interpretation that you
    asked about.

    --
    is Joshua Putnam
    <http://www.phred.org/~josh/>
    Updated Bicycle Touring Books List:
    <http://www.phred.org/~josh/bike/tourbooks.html>
    Joshua Putnam, May 26, 2005
    #10
  11. On 25 May 2005 21:15:26 -0700, in rec.photo.digital , in
    <> wrote:

    >> makes you wonder about the accuracy of the rest of the article

    >
    >Indeed, but the quick skim I did indicated there wasn't much else wrong
    >with the logic. But that bit of misinformation is not really
    >forgivable - if he knows so little about jpg files, he clearly is not
    >an expert on the topic.


    Actually I think it was just bad writing/editing. He probably meant to
    say saving but it came out all wrong.

    [snip]


    --
    Matt Silberstein

    All in all, if I could be any animal, I would want to be
    a duck or a goose. They can fly, walk, and swim. Plus,
    there there is a certain satisfaction knowing that at the
    end of your life you will taste good with an orange sauce
    or, in the case of a goose, a chestnut stuffing.
    Matt Silberstein, May 26, 2005
    #11
  12. Ron Hunter Guest

    wrote:
    > part of the WSJ technology article at
    >
    > http://ptech.wsj.com/ptech.html
    >
    >
    > "there's a difference in quality over time between JPEG -- which is
    > known as a "lossy" format because it discards, and thus loses, some
    > data each time an image is opened on your computer and then
    > recompressed as it is closed -- and formats like TIFF (for Tagged Image
    > File Format) and RAW (as in unprocessed), which preserve all the image
    > data. As debates rage about which shooting format is best (RAW is hot
    > now among chatterers at Web photo sites), a handful of guidelines has
    > emerged."
    >
    >
    > is this true -- with the jpg format the actual file on the computer
    > changes each time you view it?
    >

    NO. NOT each time you view it, ONLY each time you change and resave it.
    VIEWING does NOT cause any quality loss.


    --
    Ron Hunter
    Ron Hunter, May 27, 2005
    #12
  13. Ron Hunter Guest

    Matt Silberstein wrote:
    > On 25 May 2005 18:55:17 -0700, in rec.photo.digital ,
    > in
    > <> wrote:
    >
    >
    >>part of the WSJ technology article at
    >>
    >>http://ptech.wsj.com/ptech.html
    >>
    >>
    >>"there's a difference in quality over time between JPEG -- which is
    >>known as a "lossy" format because it discards, and thus loses, some
    >>data each time an image is opened on your computer and then
    >>recompressed as it is closed -- and formats like TIFF (for Tagged Image
    >>File Format) and RAW (as in unprocessed), which preserve all the image
    >>data. As debates rage about which shooting format is best (RAW is hot
    >>now among chatterers at Web photo sites), a handful of guidelines has
    >>emerged."
    >>
    >>
    >>is this true -- with the jpg format the actual file on the computer
    >>changes each time you view it?

    >
    >
    > No.
    >
    >

    Will wonders never cease, Matt and I agree on something! Mark this day
    on your calendars, guys.
    Grin.


    --
    Ron Hunter
    Ron Hunter, May 27, 2005
    #13
  14. Ron Hunter Guest

    Paul J Gans wrote:
    > wrote:
    >
    >>part of the WSJ technology article at

    >
    >
    >>http://ptech.wsj.com/ptech.html

    >
    >
    >
    >>"there's a difference in quality over time between JPEG -- which is
    >>known as a "lossy" format because it discards, and thus loses, some
    >>data each time an image is opened on your computer and then
    >>recompressed as it is closed -- and formats like TIFF (for Tagged Image
    >>File Format) and RAW (as in unprocessed), which preserve all the image
    >>data. As debates rage about which shooting format is best (RAW is hot
    >>now among chatterers at Web photo sites), a handful of guidelines has
    >>emerged."

    >
    >
    >
    >>is this true -- with the jpg format the actual file on the computer
    >>changes each time you view it?

    >
    >
    > No. Only if you save it again. And why would you do that?
    > After all, you are just looking at it.
    >
    > On the other hand if you manipulate your jpegs in any way, it
    > is wise to convert the jpeg to a lossless format such as TIFF
    > right away. This takes up more disk space but you can save
    > an unchanged TIFF over and over again without losing anything.
    >
    > ---- Paul J. Gans

    Better programs will NOT recompress a file if it has not been changed,
    they just exit the save with an OK status.


    --
    Ron Hunter
    Ron Hunter, May 27, 2005
    #14
  15. Mark² Guest

    <> wrote in message
    news:...
    > part of the WSJ technology article at
    >
    > http://ptech.wsj.com/ptech.html
    >
    >
    > "there's a difference in quality over time between JPEG -- which is
    > known as a "lossy" format because it discards, and thus loses, some
    > data each time an image is opened on your computer and then
    > recompressed as it is closed -- and formats like TIFF (for Tagged Image
    > File Format) and RAW (as in unprocessed), which preserve all the image
    > data. As debates rage about which shooting format is best (RAW is hot
    > now among chatterers at Web photo sites), a handful of guidelines has
    > emerged."
    >
    >
    > is this true -- with the jpg format the actual file on the computer
    > changes each time you view it?


    Yet one more reason NOT to get your technical info from a business rag...

    Jpegs ONLY lose data when re-saved in a IMAGE EDITOR.
    You can open and close the file in a VIEWER a trillion times, and not lose a
    single bit (bit...literally) of data.
    Mark², May 27, 2005
    #15
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