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Q: Storing images ( Answered 5 out of 5 stars,   0 Comments )
Subject: Storing images
Category: Miscellaneous
Asked by: seattle-ga
List Price: $5.00
Posted: 02 Jan 2003 04:30 PST
Expires: 01 Feb 2003 04:30 PST
Question ID: 136364
Greetings Google Researchers.    Given:   A few thousand 35 mm slides,
a transparency capable scanner, a fast computer, good graphics
software, and plenty of hard drive and/or DVD-RAM storage space.   
Requirements:  Save the slides as image files with maximum flexibility
for future use, including high quality hard-copy printing, while
minimizing image manipulation and overall project time.  Please advise
your recommendations including the optimum RESOLUTION for the stored
Subject: Re: Storing images
Answered By: haversian-ga on 02 Jan 2003 09:54 PST
Rated:5 out of 5 stars
Hi Seattle-ga,

Your two criteria, flexibility and speed, are at odds with each other.
 To print high-resolution hardcopies you will need the maximum
resolution, and to manipuate the files quickly, you will need a small
number of pixels.  My recommendation then would be to scan the images
at a high resolution (high-end inkjet printers are reaching ~600dpi,
and lasers can go to 1200+dpi) for print work.  You might want to
print the images ~5x as big as the original scan, so you should scan
them at roughly 5x the resolution you intend to print at.  Dithering
will reduce your effective resolution upon printing (8 red dots and
one black one in a 3x3 grid for a darker red, for example), so
somewhere in the 1200-2400dpi range should be more than you'll need
for printing.  Now, for quick manipulation and work where lower
resolution is needed, you can either scan the slides again at ~150dpi
or use a batch-capable image editing program to automatically generate
lower-resolution versions of your high-resolution scans.  You also
want as much color information as you can get, so scanning at 24 bit
(if your scanner can extract that much color info) would be a plus.

35mm slides are about 2" square, right?  At 2400dpi then, you would
have 64MB files uncompressed.  You do not want to save to a lossy
format such as jpeg if your goal is to maintain the maximum amount of
information, but some compression would make the files a bit more
manageable, and images compress well.  A google search for "lossless
image compression" (
) may be of assistance in that regard.  If you are not going to be
using the full-resolution images very often, you can zip compress
batches of them fairly easily and achieve respectable compression
ratios, though there are better compression algorithms available.  If
you opt not to compress the files, almost 2000 of them would fit on a
120GB hard drive, available for $100 if you're willing to wait for
mail-in rebates at your local CompUSA or similar.

I hope this has been helpful.  Don't hesitate to request a
clarification on any point.

seattle-ga rated this answer:5 out of 5 stars
Hi Haversian -- Very helpful, just what I needed.   Thank you!

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