Jpeg deterioration over time question?

An interesting point Dennis, and one I hadn't really thought about.
You can open the JPEG file as often as you like without affecting it , just
as long as you don't re-save it, as Rick explained.
I guess the answer is to make sure you carry out all your image alterations
in one sitting if you are going to use the JPEG format.

dennis wrote:

 > I had read where image quality can deteriorate rapidly when images are
 > saved and reloaded in JPEG format. Can someone with some expertise in
 > his area please go into laymen's detail? It recommends the tiff format
 > for high quality prints.
 > What does the article mean by "reloaded in jpeg format"?

Ian<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

"Ian Haining" <ihaining DeleteThis @corelab.co.uk> wrote in message
news:40100C5D.2E14889E@corelab.co.uk...
 > An interesting point Dennis, and one I hadn't really thought about.
 > You can open the JPEG file as often as you like without affecting it ,
just
 > as long as you don't re-save it, as Rick explained.
 > I guess the answer is to make sure you carry out all your image
alterations
 > in one sitting if you are going to use the JPEG format.
 >
 > dennis wrote:
 >
  > > I had read where image quality can deteriorate rapidly when images are
  > > saved and reloaded in JPEG format. Can someone with some expertise in
  > > his area please go into laymen's detail? It recommends the tiff format
  > > for high quality prints.
  > > What does the article mean by "reloaded in jpeg format"?
 >
 > Ian
 >

This is why people keep being told to keep the picture that comes out of the
camera in jpeg format as archive only, don't do anything to it. If you want
to edit the picture re-save it in a format that is lossless such as tiff or
psp etc. My favorite is PSP format, paint shop pro, as it will preserve any
layers used during editing then afterwards you can always save a *copy*
optimized in jpeg format for mailing or web and keep the lossless formatted
one for printing or further editing.

Rob<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

On Wed, 21 Jan 2004 22:36:07 GMT, dennis wrote:

 > I had read where image quality can deteriorate rapidly when images are
 > saved and reloaded in JPEG format. Can someone with some expertise in
 > his area please go into laymen's detail? It recommends the tiff format
 > for high quality prints.
  > What does the article mean by "reloaded in jpeg format"?

You can open and save a jpeg file a trillion times without quality loss if
the settings remain the same. Test it by opening a file in Your picture
editor. Open file x.jpg and save it as y.jpg. Then open y.jpg and save it
as z.jpg. Notice that y.jpg and z.jpg has the same filesize which should
indicate that it is the same quality. You will probably notice a change in
filesize between x.jpg and the other 2 because the compression rate and
decoding is most likely not the same.

--
Kjell Harnesk<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

On Fri, 23 Jan 2004 22:28:24 +0100, Kjell Harnesk
<nospam_kjell.DeleteThis@harnesk.d2g.nu> found these unused words floating about:

 >On Wed, 21 Jan 2004 22:36:07 GMT, dennis wrote:
 >
  >> I had read where image quality can deteriorate rapidly when images are
  >> saved and reloaded in JPEG format. Can someone with some expertise in
  >> his area please go into laymen's detail? It recommends the tiff format
  >> for high quality prints.
   >> What does the article mean by "reloaded in jpeg format"?
 >
 >You can open and save a jpeg file a trillion times without quality loss if
 >the settings remain the same. Test it by opening a file in Your picture
 >editor. Open file x.jpg and save it as y.jpg. Then open y.jpg and save it
 >as z.jpg. Notice that y.jpg and z.jpg has the same filesize which should
 >indicate that it is the same quality. You will probably notice a change in
 >filesize between x.jpg and the other 2 because the compression rate and
 >decoding is most likely not the same.

And since you can't be sure that your software (upgrades) will -always- have
the same exact algorithm and 'settings' -or- that you might open/save the
..jpg in a different program ... save in a lossless format for posterity!<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

"Kjell Harnesk" <nospam_kjell DeleteThis @harnesk.d2g.nu> wrote in message news:irfql5asttom$.54zz7ey5b4cv$.dlg@40tude.net...
 > On Wed, 21 Jan 2004 22:36:07 GMT, dennis wrote:
 >
  > > I had read where image quality can deteriorate rapidly when images are
  > > saved and reloaded in JPEG format. Can someone with some expertise in
  > > his area please go into laymen's detail? It recommends the tiff format
  > > for high quality prints.
  > > What does the article mean by "reloaded in jpeg format"?
 >
 > You can open and save a jpeg file a trillion times without quality loss if
 > the settings remain the same.

That depends entirely on the application. Some aren't very
smart and will recompress a JPEG every time it's saved, even
if nothing was changed in the image.

Rick<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

On Fri, 23 Jan 2004 14:38:00 -0800, "Rick" <me.TakeThisOut@privacy.net> wrote:

 >"Kjell Harnesk" <nospam_kjell.TakeThisOut@harnesk.d2g.nu> wrote in message news:irfql5asttom$.54zz7ey5b4cv$.dlg@40tude.net...
  >> On Wed, 21 Jan 2004 22:36:07 GMT, dennis wrote:
  >>
   >> > I had read where image quality can deteriorate rapidly when images are
   >> > saved and reloaded in JPEG format. Can someone with some expertise in
   >> > his area please go into laymen's detail? It recommends the tiff format
   >> > for high quality prints.
   >> > What does the article mean by "reloaded in jpeg format"?
  >>
  >> You can open and save a jpeg file a trillion times without quality loss if
  >> the settings remain the same.
 >
 >That depends entirely on the application. Some aren't very
 >smart and will recompress a JPEG every time it's saved, even
 >if nothing was changed in the image.
 >
 >Rick
 >

Right. JPEG is fine for archival and you can open it a trillion
times over the next century without degradation. And you can copy it
or move it. But JUST DON'T SAVE IT or you might lose some resolution.
PJ<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

On Fri, 23 Jan 2004 14:38:00 -0800, Rick wrote:

 > "Kjell Harnesk" <nospam_kjell.TakeThisOut@harnesk.d2g.nu> wrote in message news:irfql5asttom$.54zz7ey5b4cv$.dlg@40tude.net...
  >> On Wed, 21 Jan 2004 22:36:07 GMT, dennis wrote:
  >>
   >>> I had read where image quality can deteriorate rapidly when images are
   >>> saved and reloaded in JPEG format. Can someone with some expertise in
   >>> his area please go into laymen's detail? It recommends the tiff format
   >>> for high quality prints.
   >>> What does the article mean by "reloaded in jpeg format"?
  >>
  >> You can open and save a jpeg file a trillion times without quality loss if
  >> the settings remain the same.
 >
 > That depends entirely on the application. Some aren't very
 > smart and will recompress a JPEG every time it's saved, even
 > if nothing was changed in the image.

Maybe so, but then it is a flaw in the software, not in the jpeg format.

--
Kjell<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

"Kjell Harnesk" <nospam_kjell DeleteThis @harnesk.d2g.nu> wrote in message
news:q4wx79q1z1mn$.1odnprsobzcrx.dlg@40tude.net...
 > On Fri, 23 Jan 2004 14:38:00 -0800, Rick wrote:
 >
  > > "Kjell Harnesk" <nospam_kjell DeleteThis @harnesk.d2g.nu> wrote in message
news:irfql5asttom$.54zz7ey5b4cv$.dlg@40tude.net...
   > >> On Wed, 21 Jan 2004 22:36:07 GMT, dennis wrote:
   > >>
   > >>> I had read where image quality can deteriorate rapidly when images
are
   > >>> saved and reloaded in JPEG format. Can someone with some expertise in
   > >>> his area please go into laymen's detail? It recommends the tiff format
   > >>> for high quality prints.
   > >>> What does the article mean by "reloaded in jpeg format"?
   > >>
   > >> You can open and save a jpeg file a trillion times without quality loss
if
   > >> the settings remain the same.
  > >
  > > That depends entirely on the application. Some aren't very
  > > smart and will recompress a JPEG every time it's saved, even
  > > if nothing was changed in the image.
 >
 > Maybe so, but then it is a flaw in the software, not in the jpeg format.
 >
 > --
 > Kjell

In fact there is no reason to save it after opening it if there has been
nothing done to it, just close it and it will still be sitting there in your
folder. On the other hand some software will save a jpeg that is being
edited at the same compression of the original when clicking the Save icon
whereas other software will bring up the optimization dialogue.

Rob<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

On Sat, 24 Jan 2004 14:50:33 -0000, Canopus wrote:

 > In fact there is no reason to save it after opening it if there has been
 > nothing done to it, just close it and it will still be sitting there in your
 > folder.

Of course.

 > On the other hand some software will save a jpeg that is being
 > edited at the same compression of the original when clicking the Save icon
 > whereas other software will bring up the optimization dialogue.

And some will save with the default settings without asking.

--
Kjell<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

On Fri, 23 Jan 2004 22:28:24 +0100, Kjell Harnesk
<nospam_kjell RemoveThis @harnesk.d2g.nu> vaguely proposed a theory
.......and in reply I say!:

OK. Roving brain and imagination at work. Much opinionated input and
processing. Little data. "Frustrated ignorance" results.

 >You can open and save a jpeg file a trillion times without quality loss if
 >the settings remain the same.

Ahah! Bingo!..........but not sure....:-<

_If this is true_ then it gels with what I thought.

However. How do you know what "settings" the camera used? If you save
as something else you lose straight away.

The programme decodes each time it opens. If you save at the same
ratio each time then it _should_ not cause degradation.

BUT
JPEG compression relies on shades of colour etc(???). So the same
compression ratio causes different file sizes and losses for different
processes...sharpness etc.

Y'all come back ya hear! please.
**************************************************** sorry
remove ns from my header address to reply via email

c<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question? 

Here's my tuppence worth

The JPEG format is a lossy compression format not lossless.
When you open a JPEG file, what you get is not the original file, so when
you then re-save the file, you are compressing a different image than the
one you originally compressed, so even if you are using exactly the same
settings you are going to lose some more quality ("lose" might be confusing
because you will still have the same size of file, but nevertheless, the
information in the file will be just that little bit less like the
original).
Take a look at the following link

<a style='text-decoration: underline;' href="http://www.faqs.org/faqs/jpeg-faq/part1/section-10.html" target="_blank">http://www.faqs.org/faqs/jpeg-faq/part1/section-10.html</a>



dennis wrote:

 > I had read where image quality can deteriorate rapidly when images are
 > saved and reloaded in JPEG format. Can someone with some expertise in
 > his area please go into laymen's detail? It recommends the tiff format
 > for high quality prints.
 > What does the article mean by "reloaded in jpeg format"?

--
Regards
Ian Haining
Systems Administrator
Core Laboratories (U.K.) Ltd

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 >> Stay informed about: Jpeg deterioration over time question? 

If I rotate a jpeg in Irfanview, am I screwing it up when I save it to replace
the original in the same folder? The sizes look the same.
 >> Stay informed about: Jpeg deterioration over time question? 

On Fri, 30 Jan 2004 03:37:21 GMT, "Cymbal Man Freq." <Don't
Bother.TakeThisOut@ForgedPostsAnonymous.unorg> wrote:

 >If I rotate a jpeg in Irfanview, am I screwing it up when I save it to replace
 >the original in the same folder? The sizes look the same.
 >
If it is about the same size, I doubt you are losing anything
noticable.
I'd say you/we are worrying way too much about this. You now have
a usable picture. So what if you lose a little.

PJ<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Jpeg deterioration over time question?