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Re: Scanning

Even if everyone imports their images into Photoshop their are huge
differences in the scanning software's interface.  The scanner has software
to provide a preview and perhaps scaling and resolution options etc.
These programs all do similar things but don't always look or work the
same. I use a Microtek 24 bit scanner for most work.  It uses a proprietary
program called ScanWizzard.  The reason your scan come out different sizes
is most likely due to not planning for the end use ahead of time.

1.  If you intend to PRINT the scan you must size it by dpi (a scale base
output to paper in inches)
2.  If you intend to VIEW the scan on a computer screen you must size it by
ppi (based on the number pixels displayed per inch)

The image size in inches will always PRINT the same in Photoshop but the
same image will resize on your computer screen depending on the monitor
size in Pixels.

A 640 x 480 pixel will image will fill a 14inch Monitor but will look
smaller on a 800 x 600 laptop or smaller still 1024 x 768 monitor.   The
number on pixels are the same but the space around them increases.

If you size your image to print 8x10 inches it will display MUCH bigger on
the computer screen.  Maybe only 8% will fit.

Experiment with your scanner.  Set up to scan a 4 x 6 inch photo at 72 dpi
resolution @ 100%.  Look at the file size.  Now change any element...go to
600 dpi and look how the file size increases.  Change your resolution back
to 72 dpi (the max res for most computer monitors) and change the image
enlargement size to 150% and again see the change in file size.

Many problems are created by not understanding the interrelationship of all
these factors and how they effect the file and image size.

Your scanning is controlled by the output...monitor (pixels) or screen
(inches) Photoshop will display both measurements of any file in the drop
down menu.

For print, set your scanner for inches and the max real optical resolution
of the printer, 300 dpi, 600 dpi, etc.  Don't bother with any setting that
is greater than your printer.  If the true, non-interpolated resolution of
your scanner is higher than your printer, output to a better printer
somewhere else.

The minimum res for type "should be" 1200 dpi but scan as high as your
equipment can and see how it looks to YOU.

Many service bureaus ask for a minimum file size and just calculate the
output.  Like this:

I want them to enlarge and print my 8" x 10" photo to 80" x 100" (I have
lots 'o cash!)  at 150 dots per inch.  If I can scan my photo 100% of the
8" x 10" @ 1500 dots per inch, the service bureau can take that scan and
instead of printing @ 1500 dpi, they will resize the image to 80" by 100",
making it 10 times bigger in size and at the same time dropping the
resolution of the output automaticly to 150 dpi.  The file size (total
number of dots) will always stay the same, but the dots will be closer or
further apart depending now you change the resolution or image (output) size.

I know this can be confusing, that's why the file size is what some folks
use. Not all scanners have a friendly interface.  That's why I like
Microteks.  All the options can be set and reset while you keep an eye on
how the file size changes.  I have a cheap slide scanner that I have to
scan a 35 mm slide @1200 dpi to print around 8.5 x 11, because the original
is so small and the scanner has no scale option, just resolution and % of
image settings.

In short, this is all very dependant on what equipment controls you have
and how you wish to use them.  They're are several ways to arrive at the
same place because of the interrelation ship of all these parameters.  Look
for a book called Digital Imaging for Artist by Grotta. It is a bit dated
in terms of equipment, but it cover the basics well.

Regards...hope this answers a few questions.


At 08:48 AM 5/11/99 +0300, you wrote:
>I don't know if this list is the appropriate place for this question,
>but I don't know who else to ask.
>I have a flat bed scanner, and when I scan an image (to develop into a
>plate for printing or to send via e-mail) it comes out HUGE. I blew my
>brother's computer out of the sky by sending him a standard snapshot
>without checking it.
>The only way I have been able to send images is by resizing them
>drastically, which I find very tedious. I can't find any reference to
>controling the size of the initial scan, either in the hopelessly
>inadequate manual, the help files, or the web.
>Any ideas?
>Best regards,
>Yehuda Miklaf
>Shalom Yehuda Press

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