TIFF (Tag Image File Format) allows many different types of compression
(at least 5 different algorithms). The principal difference from JPEG
(Joint Photographic Experts Group) is that TIFF compression algorithms
are "lossless" and JPEG is "lossy".
"Lossless" means that compression has been achieved by removing only the
truly redundant information. When the image is decompressed all of the
detail of the original uncompressed version will be restored.
"Lossy" means that some information is irretrievably lost. When the
image is decompressed it's not quite up to the original. Some
information was thrown away to achieve better compression. All else
being equal, the higher the compression the more the image quality will
suffer.
If you want to retain every possible bit of information then don't use
JPEG. If you want to save a lot of space at the cost of a little bit of
image quality then use JPEG. JPEG is popular since it does allow
dramatic size reductions with only a small effect on image quality.
JPEG also allows you to vary the amount of compression so you can decide
how much quality to trade off for more or less space.
The thing to remember about JPEG is that, once it has been applied, the
result has less detail than the original. If you decide you want to
change the compression again do it from the original uncompressed image
or one restored from a lossless compression method. Working from a
decompressed JPEG image means that you are working with less data than
you started with. Each step done like this will lead to more and more
deterioration of the image. A simple analogy might be like trying to
create a print by rephotographing another print instead of going back to
the original negative.
ps: I don't know a blasted thing about scanning, processing or printing
photos electronically. But I do know a bit about data compression.
Chuck Norcutt
Woburn, Massachusetts
----------------------------------------------------
I have one last question...I know TIFF is uncompressed and jpg is a
compressed format to make it quicker to send online, tec. But as far as
for printing, does the compression change the results?? How?? I probably
already know the answer, but I never realized that the format could
affect the outcome of a print itself???? (duh??)
:=)
Susan
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