Scanning...
is a mysterious for several
reasons: a lack of understanding resolution; not knowing the optimum resolution
needed for output media and limited scanning software.
Resolution:
Let's first look at understanding resolution. As we discussed, there
2 aspects of "File Resolution"... Line (sharpness) and Brightness
(depth). When scanning the first 2 areas to consider are, "file
line resolution" and second is output or "print line resolution".
Because of my background in photography, I like to make analogies
to the photographic process. In conventional photography, no one seems
to have trouble with the concept that the resolution of your image
(both sharpness and color) is determined when you acquire it... clicking
the shutter. This is no different in the digital world. It is the
same when we click the shutter in a digital camera but it gets pretty
mysterious when we use a flat bed or transparency scanner to acquire
the image. Instead of a piece of film or a mega-pixel CCD in a digital
camera, the file line resolution of the image is determine
by the number of inches scanned times the the scan rate (in pixels).
A 4 sq. inch print scanned at a rate of 100 PPI will give us a file
line resolution of 400 x 400 pixels. A 1 sq. inch area of a negative
scanned at 400 PPI will give us the same file line resolution of 400
x 400 pixels. Your image resolution, just like in photography, is
determined at the point of capture... this IS your "file line
resolution"...done ...final ...fini!
| Now
you can do two things with this resolution... redistribute it
over paper of various size (called Resizing)
or make a new sample with more or less pixels called
Resampling. "Resampling"
is usually not a good thing but this is a topic itself and we're
talking about scanning here. |
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Resolution
Needed for Output:
If we now understand that resolution is determined at point of capture,
the question is how much resolution do we need...
(Click
for more info)
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Scanning
Software:
Finally, and most importantly, the scanning software. This
is an area that most do not consider when purchasing a scanner...
even the manufacturer! For me it is one of the most important consideration.
There are 3rd party scanning software that are made for the more popular
scanners and can cost more than the scanner itself! I have always
used Microtek scanners because of their software. With a versatile
software and an understanding the first two points above, scanning
can be easy! Did I say SCANNING and EASY in the same
sentence? Sure, if your software allows you to set and lock
the final output size and resolution all you need to do is:
1)
set the desired final print size and desired resolution (lock
it);
2) drag the bounding box to select the area of the sample to
scan - the software will maintain the final print shape (see
Power Tip below) and select the scaling % necessary;
3) then press the scan button... as easy as 1, 2, 3! |
When you open the scanned file in Photoshop and view it under the
menu >Image >Image Size, you'll see you document size and resolution
just as you desired. Magic Happens!
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...Now,
did we mention scanning considerations for Color Resolution
and Pixel Distribution?
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More
Scanning Tips
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