]
[mailto:[EMAIL PROTECTED]]On Behalf Of Derek Clarke
Sent: Tuesday, April 03, 2001 12:04 PM
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: RE: filmscanners: File format
The difficult part is re-saving the file with the same compression ratio
as it had originally.
Even the mighty
That wouldn't help as different programs use different scales in their
Options or Save As boxes to determine JPEG compression levels, there
doesn't seem to be a standard.
Also as other people in this thread have pointed out, even repeatedly
saving the file at the same compression level in the
I have to agree with Hugo here. His explanation is what I always read
and learned, and it also makes perfect sense.
The only very slight disagreement I'd have is that it might be possible
that if you open and save in JPEG format enough times, you might
actually reach a point where you are
ths of jpeg compression
care to comment and suggest reasons for the discrepancy,
please?
Or maybe Henk's and my results need repeating, like cold
fusion and life on Mars?
Alan T
- Original Message -
From: Hugo Gvert [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Monday, April 02, 2001 12:44
The only very slight disagreement I'd have is that it might be possible
that if you open and save in JPEG format enough times, you might
actually reach a point where you are "chasing your tail" and that
certain random pixels will change one way one time and then
--- You wrote:
Anyway, I just know I'm going to be nit-picked to death about my very
simplified descriptions to what are very complex mathematical functions,
but I hope this is somewhat helpful in explaining the differences
between JPEG and other compression methods, and why a photograph shows
in
data or quality.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Larry Berman
Sent: Thursday, March 29, 2001 8:31 PM
To: [EMAIL PROTECTED]
Subject: Re: filmscanners: File format
What would be the point of storing and reopening and saving
I've been holding off weighing in on this subject area because I'm not
expert but I may be able to shed some light. I just ran some experiments and
I put the images into a directory on our website:
http://www.asf.com/temp/. Our webmaster helped out by converting all the
tifs to jpegs for viewing
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: RE: filmscanners: File format
The difficult part is re-saving the file with the same compression ratio
as it had originally.
Even the mighty Photoshop just uses one compression ratio for all JPEG
file saves. That compression ratio can be set manually
Your results will vary depending on the image you use. I hope this data is
useful. Your conclusions will vary depending on your needs obviously.
I did a similar test using a 1k by 1k piece out of the PhotoDisc test image.
The original image is extremely sharp and contains nice flesh tones and
Derek wrote:
The difficult part is re-saving the file with the same compression ratio as
it had originally.
Even the mighty Photoshop just uses one compression ratio for all JPEG file
saves.
You can save at the same compression ratio, but that doesn't mean much. I
noticed this several months
I just ran some experiments and
I put the images into a directory on our website:
http://www.asf.com/temp/. Our webmaster helped out by converting all the
tifs to jpegs for viewing (uh-oh). I've asked him to convert them back,
The converted-back ones will be just
Without wishing to add to you "pain" ;-), I was surprised to determine
that this exact situation (the "leveling" of the compression) occurs
much sooner than I expected. You will probably have noted that via my
recent posting to that effect, where I monitored file sizes after
repeated Jpeg
Hey, Bill... your webmaster also made those files password protected
Mike M.
Bill Ross wrote:
I just ran some experiments and
I put the images into a directory on our website:
http://www.asf.com/temp/. Our webmaster helped out by converting all the
tifs
debate and caused everyone to go to all this experimental trouble
testing out their positions. :-)
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Arthur Entlich
Sent: Tuesday, April 03, 2001 3:16 AM
To: [EMAIL PROTECTED]
Subject: Re: filmscanners: File for
It seems the algorithm rather rapidly reaches the point of "no further
benefit" and stabilizes the file size, and likely also the amount of
change in the pixel structure.
Yes, perhaps with variations of degree between programs. Until
a lower-quality rating is
On Fri, 30 Mar 2001, Henk de Jong wrote:
Laurie Solemon wrote:
Out of curiosity, how many timed did you do this and what sorts of
changes did you see?
I took a picture, saved, closed and re-opened it ten times.
After every step (save, close and re-open) I compared the new image with the
PM
Subject: Re: filmscanners: File format
Come on guys, what happens when you save with jpeg or any
other
compression that loses data? You save the file, the
compression algorithm
desides what information can be thrown away, and then saves
it..
Each time there would be some generational loss.
Not necessarily true. If you open and close ( or resave) the compressed
file
without changing the compression from one quality level to another in the
case of .jog or without resampling the image prior to closing or resaving
the file, there
Maris said:
Just a note on LZW compressed image portability - I have
run into one
instance where an LZW compressed image was not portable -
when exporting a
48-bit compressed TIFF from Vuescan to Corel PhotoPaint 9
it opens but the
image is unrecognizable. If exported uncompressed there
is
? that we photographers are "over do it " when we are
delivering pictures in big tif or psd files.
Mikael Risedal
Lund
Sweden
From: "Laurie Solomon" [EMAIL PROTECTED]
Reply-To: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Subject: RE: filmscanners: File format
Date: Thu,
On Fri, 30 Mar 2001 09:49:05 +0800 httin ([EMAIL PROTECTED]) wrote:
Did any one knows whether is there any informations/details loses when
store in compressed JPG format in maximum quality 10 and while you keep
opening and saving the same file many times?
If you merely open and save a
ot; [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Friday, March 30, 2001 4:08 PM
Subject: RE: filmscanners: File format
Mikael wrote:
I think there are some myths about jpg. tif. psd. and high quality
printing
pictures.
We (printing company, myself and a medical company picture bank)
have done
: RE: filmscanners: File format
Mikael wrote:
I think there are some myths about jpg. tif. psd. and high quality printing
pictures.
We (printing company, myself and a medical company picture bank)
have done tests about saving pictures that later can used to print out on
high glossy paper.
All
?
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Henk de Jong
Sent: Friday, March 30, 2001 12:59 AM
To: [EMAIL PROTECTED]
Subject: Re: filmscanners: File format
Each time there would be some generational loss.
Not necessarily true. If you open and close
, 2001 1:40:00 PM GMT
Subject: Re: filmscanners: File format
On Fri, 30 Mar 2001 09:49:05 +0800 httin ([EMAIL PROTECTED]) wrote:
Did any one knows whether is there any informations/details loses when
store in compressed JPG format in maximum quality 10 and while you keep
opening and saving
save
routine, because each has its own scale and criteria for
'jpeg quality'.
Regards,
Alan T
- Original Message -
From: Lynn Allen [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Friday, March 30, 2001 5:57 PM
Subject: Re: filmscanners: File format
]
Sent: Friday, March 30, 2001 5:51 PM
Subject: RE: filmscanners: File format
Out of curiosity, how many timed did you do this and what
sorts of changes
did you see? Have you tried the same experiment using
another image editing
program to eliminate the possibility that it might be more
D]
Subject: Re: filmscanners: File format
Tony wrote:
If you merely open and save a JPEG at the same compression, without
editing, you lose nothing. If you edit, you lose information. It's
impossible to quantify how much, since it varies depending on the image and
what you do to it.
That's right
Laurie Solemon wrote:
Out of curiosity, how many timed did you do this and what sorts of
changes did you see?
I took a picture, saved, closed and re-opened it ten times.
After every step (save, close and re-open) I compared the new image with the
original and found small differences, we all
//
Thank you for every one who participate my question.
Now I got the point.
HT Tin 31st/Mar/2001
//
Tony Sleep wrote:
On Fri, 30 Mar 2001 09:49:05 +0800 httin ([EMAIL PROTECTED]) wrote:
Did any one knows whether is there any informations/details loses when
store in compressed JPG
Did any one knows whether is there any informations/details loses when
store in compressed JPG format in maximum quality 10 and while you keep
opening and saving the same file many times?
And how about the raw file TIFF?
Thanks.
HT Tin
What would be the point of storing and reopening and saving the same image
in a compressed format repeatedly. Each time there would be some
generational loss. Store in an uncompressed native format to your graphics
program. If you open a jpeg in Photoshop it automatically takes on the
larry wrote:
What would be the point of storing and reopening and saving
the same image in a compressed format repeatedly. Each time
there would be some generational loss.
This is only true of lossy compressed formats like jpeg and PCD.
Store in an uncompressed native format to your
Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of httin
Sent: Thursday, March 29, 2001 7:49 PM
To: filmscanners
Subject: filmscanners: File format
Did any one knows whether is there any informations/details loses when
store in compressed JPG format in maximum quality 10
losses in
data or quality.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Larry Berman
Sent: Thursday, March 29, 2001 8:31 PM
To: [EMAIL PROTECTED]
Subject: Re: filmscanners: File format
What would be the point of storing and reopening and saving the same
Hi Rob,
The original question was asked about repeatedly opening and saving as a jpeg.
larry wrote:
What would be the point of storing and reopening and saving
the same image in a compressed format repeatedly. Each time
there would be some generational loss.
Rob wrote: This is only true
]
Subject: RE: filmscanners: File format
Each time there would be some generational loss.
Not necessarily true. If you open and close ( or resave) the
compressed file
without changing the compression from one quality level to another in the
case of .jog or without resampling the image prior
, and
once in PhotoPaint it can be compressed using LZW. This appears to be one
exception.
Maris
- Original Message -
From: "Rob Geraghty" [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Thursday, March 29, 2001 10:15 PM
Subject: Re: filmscanners: File format
| larry wrote:
|
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