> After learning the disadvantages of using JPG
> to archive documents I decided to experiment a bit
> since I have been using JPG to archive black/white
> documents for years and thought I was getting good
> quality and saving space.
I am an ex-sailor myself, and I don't know if your "Gob" refers to same,
but let me say it seems like it might take a whack in the face from the
main brace to convince you that JPEG format has drawbacks in image quality.
First, the eye is the worst definer of quality becuase it could be
fooled by images with as little density as one dot per inch if the
distance of viewing is great enough.
The point of this discussion is "archiving" of documents for later
retrival and manipulation. This includes enlargement and printing, both
of which might cause degradation.
> Today I scanned a document, actually yellow
> paper with black printing, using the following settings:
> 200 dpi
> sized 67%
> After scanning I adjusted the gamma up a
> bit and the contrast and brightness up a bit until
> the grey of the background was white and the
> printing was sharp and black then I saved the file
> in JPG (75% progressive compression) and in TIF
> The JPG file is 299 kb, the TIF file is 1.6 mb.
The mistake your making here is that changing the yellow or gray or any
uniform background color with your software is reducing the file size.
It depends on your software and what format and compression scheme you
are using and exactly how your particular program manipulates the image
for what the resulting file size will be. Not every software will
produce the same results just because the file format extension is the
same. This only means that the result shares some commonality, not that
the manipulation is done exactly the same.
Any single color would be compressed the same as white which in computer
code is just the same as any other color as far as the amounts of bits
and bytes it takes to represent that color. White to your printer means
no ink, but to the code in the image file it does not mean blank or
What the compression does is take long strings of the same color and by
its algorithm represents it with less space.
Secondly, all of the recommendations regarding TIFF for archiving are
for COMPRESSED files. You are comparing compressed JPEG with
Statements such as this can be found in many places by using your search
"A Note About JPEG File Compression
A number of our vendors offer their images in JPEG format. When using
JPEG images no image degradation is noticeable after a single
compression/decompression cycle. However, further compression(s) to and
from the JPEG format will degrade the image quality to an extent that
eventually it will become invisible. To retain maximum quality in these
images simply avoid re-saving the image in JPEG format and use
uncompressed formats such as TIFF or EPS or a loss-less compression
format such as TIFF with LZW compression."
another site with just about everything on jpeg info:
Many questions answered in straight forward manner here:
A page to start re TIFF (dated 1997 and some info is not the same today,
and there are many more softwares which incorporate .tif capability.)
> When I call them back into Photo Impact and
> display them side by side I can see a tiny bit of
> difference. The JPG file is very slightly less crisp
> but both are perfectly readable. The printouts
> seem to be identical.
Again, what is the criteria you wish for acceptability: computer screen
readabiliy, printout readability, archival manipulation, small file
sizes, common and inexpensive software, etc. There are trade-offs.
There would be no sense discussing maximum aircraft speeds if we limit
the discussion to non-jet engine types. So unless you begin with some
assumptions and limits there will be no point to hashing around about
the various algorithms for compression if you are limited to only one
which came with a particular program.
> How can I do better than the JPG version
> of this document, either size or quality wise? I'd
> be interested to know.
The current consensus which you can review by using your search engine
with "TIFF file format" or "TIFF file compression" or "image format"
and refining and directing your search will give your more technical
stuff than you wish. Sort and hunt until you find sites that speak on a
level you can understand and I think you'll come to some acceptance of
this as the currently popular choice.
> Jerry Hale
> Deltona, FL