I have to confess that in making the transition from working with the
printed page to the virtual one, the scanner initially caused me a
little confusion. Actually, it still does.
Let us take a few moments to explore a few myths and legends regarding
our trusty scanners.
What kind of scanner should I buy?
As with anything else in life, having the right tool for the
job helps a great deal. For the most part, you will find the
following types of scanners on the market:
Roller Feed: These little numbers are great for
doing faxes and OCR, but lack the precision in handling
needed for working with photos. They also can bend your
pictures.
Photo Sized: Usually comes as a fixed format
3"x5" or 4"x6" box that sucks the photo in, scans it, and
spits it out. Not good at working with the wrong size photo,
especially larger ones. ;-)
Hand Held: These were popular for a while. About
the only use I could find for one is scanning an image that
is glued to a wall.
Flatbed: This is just what you want to buy! Perfect
for working with all sized photos. Of course, not convenient
for faxing, but this is not about faxing.
Do yourself a favor and purchase a flatbed scanner. These models
have come down a great deal in price. In fact, I have seen my
year old scanner fall in price from about $500 to $149. We won't
talk about the digital camera that I just had to have.
If 300 DPI is good, then 1200 DPI must be better!
Resolution on scanners and printers is measured in DPI or
Dots Per Inch. When working with the monitor, we tend
to deal with pixels. A pixel is the smallest area of the
screen that we can set the color for.
Here is our problem. A printer, even an inexpensive one is
more than capable of printing 300 DPI. In fact, the resolution
is adjustable. Not so with our monitor. It is basically stuck
in a fixed resolution. Here is why:
No matter what size monitor you own, there are typically
a few different resolutions, or pixel settings you might
select from. I have a 17" monitor that measures about 12.5"
across and about 9" down. So in terms of thinking of things in terms of
paper resolution, I have a problem.
Resolution
Horizontal DPI
Vertical DPI
640X480
51
51
800x600
64
64
1024x768
82
82
1280x1024
102
102
As you can see from the chart above, the best resolution of about
102DPI occurs at the 1280x1024 setting. I don't know about you, but
my eyes can't cope with anything beyond 800x600. That means that I
view my images at a resolution of only 64 DPI! Unless I am doing
major enlargement of a tiny photograph, anything beyond 150 DPI or
so for web work is a waste of money!
Can't I get a better image with a higher resolution?
Okay. I have to admit I am tight for cash at the moment, so
let's take an object that is fairly familiar, and thankfully
inexpensive.
The penny below was scanned at three resolutions. As you can
see, The higher the resolution, the bigger the penny! We did
not get a finer image, but only a larger one.
72 DPI
100 DPI
125 DPI
3950 Bytes
6,163 Bytes
9,679 Bytes
Note: I used GIF to avoid distortion.
Can I fool it by lying about the HEIGHT & WIDTH?
What if we set the HEIGHT and WIDTH of all of our images
to the size of the low resolution image? Maybe that will
give us a better looking image.
Obviously the laws of physics are still holding. You can
only fit so many pixels on the head of monitor! I can't see
much difference other than the highest resolution image
requires almost three times as many bytes as the smallest.
72 DPI
100 DPI
125 DPI
3950 Bytes
6,163 Bytes
9,679 Bytes
What about color resolution?
For our purposes, 16.7 million color (24 bit) does the job. Many
inexpensive scanners are 30 bit, so if you want, go for it! One
piece of advice is to scan the image at 16.7 million color, and
use your image editing software to do color reduction if needed.
You will be happier with the results that way.
