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Wall Street Journal - technology report on digital cameras

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Anonymous
May 25, 2005 10:55:17 PM

Archived from groups: rec.photo.digital (More info?)

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?
Anonymous
May 25, 2005 11:06:43 PM

Archived from groups: rec.photo.digital (More info?)

>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 25, 2005 11:37:32 PM

Archived from groups: rec.photo.digital (More info?)

<chrlz@go.com> 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
Related resources
Anonymous
May 26, 2005 1:15:26 AM

Archived from groups: rec.photo.digital (More info?)

> 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.
Anonymous
May 26, 2005 2:43:53 AM

Archived from groups: rec.photo.digital (More info?)

In article <1117072517.926550.25570@g47g2000cwa.googlegroups.com>,
nospam650@yahoo.com 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.

--
josh@phred.org is Joshua Putnam
<http://www.phred.org/~josh/&gt;
Updated Bicycle Touring Books List:
<http://www.phred.org/~josh/bike/tourbooks.html&gt;
Anonymous
May 26, 2005 2:55:25 AM

Archived from groups: rec.photo.digital (More info?)

nospam650@yahoo.com 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: mrmnews@the-meissners.org
http://www.the-meissners.org
Anonymous
May 26, 2005 3:17:33 AM

Archived from groups: rec.photo.digital (More info?)

On 25 May 2005 19:06:43 -0700, chrlz@go.com 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.
Anonymous
May 26, 2005 3:42:14 AM

Archived from groups: rec.photo.digital (More info?)

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.
Anonymous
May 26, 2005 7:11:04 AM

Archived from groups: rec.photo.digital (More info?)

On 25 May 2005 18:55:17 -0700, in rec.photo.digital ,
nospam650@yahoo.com in
<1117072517.926550.25570@g47g2000cwa.googlegroups.com> 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.
Anonymous
May 26, 2005 7:51:10 AM

Archived from groups: rec.photo.digital (More info?)

nospam650@yahoo.com 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
Anonymous
May 26, 2005 5:26:38 PM

Archived from groups: rec.photo.digital (More info?)

On 25 May 2005 21:15:26 -0700, in rec.photo.digital , chrlz@go.com in
<1117080926.109770.150760@f14g2000cwb.googlegroups.com> 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.
Anonymous
May 27, 2005 12:57:39 AM

Archived from groups: rec.photo.digital (More info?)

nospam650@yahoo.com 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 rphunter@charter.net
Anonymous
May 27, 2005 1:00:17 AM

Archived from groups: rec.photo.digital (More info?)

Matt Silberstein wrote:
> On 25 May 2005 18:55:17 -0700, in rec.photo.digital ,
> nospam650@yahoo.com in
> <1117072517.926550.25570@g47g2000cwa.googlegroups.com> 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 rphunter@charter.net
Anonymous
May 27, 2005 1:01:47 AM

Archived from groups: rec.photo.digital (More info?)

Paul J Gans wrote:
> nospam650@yahoo.com 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 rphunter@charter.net
Anonymous
May 27, 2005 1:51:08 AM

Archived from groups: rec.photo.digital (More info?)

<nospam650@yahoo.com> wrote in message
news:1117072517.926550.25570@g47g2000cwa.googlegroups.com...
> 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.
!