>A well known medical newspaper printed on high glossy paper wants their
>pictures files in .jpg level 5 .!!!!!!They must also have done some test
>there jpg.5 level seems to suite there needs.
Lynn, your example leave the reader to make a lot of assumptions with no
real empirical basis for making them. Since most of the talk that I know of
concerning degradation of compressed files tends to be related to .jpg files
that are save and resaved a number of times at different quality levels
resulting in the possible introduction of artifacts ( color and otherwise)
or in compressed files being opened and resampled and then resaved as a
compressed file resulting in the lose of image data, the fact that someone
would want files submitted in .jpg format at a given level does not tell use
if these files are being opened and resaved at the same quality level of
compression or at different ones or any of the other conditions of their
testing which may have underlined such a request involved saving and
resaving the files at the same quality level or not so as to have any
bearing on comments regarding the potential for file degradation.
As noted degradation of .japg files has been said to take place typically
with multiple saves and resaves at different quality levels - this often
does not mean it takes place with regularity after one or two or three such
opening and saving operations. As for other compression schemes, I have
only heard of real problems taking place when one resample between opening
and resaving of the compressed file or some times the use of unsharp mask
before resaving to the compressed file.
-----Original Message-----
From: owner-filmscanners@halftone.co.uk
[mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Lynn Allen
Sent: Friday, March 30, 2001 8:09 AM
To: filmscanners@halftone.co.uk
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 tests about saving pictures that later can used to print out on
high glossy paper.
All files are scanned in 350 ppi
We compared a tif file and a jpg file in level 7 ( Photoshop 5.0)
Proof printing 2 picture.
No one could se any difference in the 2 pictures in colors. A closer look
with magnifier glasses shows some differences in a small text.
We took the same jpg file and resaving it up to 5 times. We looked at each
step and where suppriced of the small changes of colors in the picture.
Example:
A well known medical newspaper printed on high glossy paper wants their
pictures files in Jpg level 5 .!!!!!!They must also have done some test
there jpg.5 level seems to suite there needs.
Conclusion:
This must means? that we photographers are "over do it " when we are
delivering pictures in big tif or psd files.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
This is something I've suspected for some time now (about the
compressions--I *knew it* about the photographers! ;-) ).
Thanks for the post, Mikael!
Best regards--LRA
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