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Ancestry Daily News
11/21/2002 - Archive
Rootsworks: Scanners
Since I wrote about scanners in December 2000, some things have changed. For
example, if you do a Web search on "new scanning technology" you'll
find numerous entries related to scanning for explosives, not images. Scanners
are electronic devices that convert paper documents into electronic images.
They are very "numbery" toys—the resolution and image sizes, the
number of colors-it's daunting to the newcomer. The images themselves are very
big sets of 1s and 0s. Let's see if we can break these numbers down into something
we can use.
What Is It?
A scanner shines a light on a document and records a lot of dots. If the
image format is black and white, each dot is either black or white. Most scanners
record 256 shades of each primary color. That takes 8 "bits" for each
color. You'll sometimes see options for scanning in "24-bit" color.
After those dots are converted to electrical pulses, they're converted into
a number, by "digitizing." The point of bringing up the math here
is that the files grow quite fast as we gather more information about each dot
we scan.
The user has a wide choice of resolutions, and the arithmetic to figure out
how to get the best image would be a challenge for a math major. If you look
at some of the explanations in the links section of this article, you'll see
that you have to convert scanned resolution, in "dots per inch" to
printed resolution, in "lines per inch," or screen resolution, in
total dots per screen. A general guideline is that if you scan at resolutions
that can't be output by your screen or printer, you will only obtain a slightly
better looking image and you might take up a LOT more disk space.
I've seen a number of cases where a genealogist has two census citations, where
the ancestor's family lived in one state in one census and another state in
the next one. If your scanner is a 600 dpi scanner, and you scan an image at
9600 dpi, the computer does something a lot like what genealogists do - they
connect the dots with ones that they make up. From an information honesty perspective,
I don't like the idea of creating records with data that I just make up, or
that a machine just makes up for me. I'd suggest that you not exceed the rated
resolution of your scanner when creating historical records!
Name Two Of Them
There are several types of scanners, but in my opinion the only ones to
think about buying are the flatbed scanners. Hand-helds are a little harder
to get good images from. There is a pen-type scanner that will read lines from
documents, but I still prefer making copies and scanning whole sheets. There
are some big differences in price, but these days you can buy a better scanner
for under $50 than you could buy for $1,000 in 1990. The biggest differences
in any two scanners these days are the price and the connection method (parallel,
SCSI, and USB).
What's The Down Side?
There aren't many down sides to scanner use. Of course, if you get a scanner
you're going to want to have a lot of free disk space to put all of those pictures
on. You'll have to learn to choose which images to keep and how to let go of
the other ones, which is a big challenge for a genealogist. In times past, there
was a problem with complicated setup, but that's much easier now.
How Do I Know If It's Not Working?
I only see two kinds of problems: bad connections and wrong settings. As
a rule, if you set up your scanner properly it will keep working all the time,
but occasionally I have the scanner turned off when the PC comes up and the
scanner won't work. When that happens, restart the PC. If you scan a document
with the wrong settings, you can usually either re-scan it or change the image
in a graphics program.
What If I Change Computers?
Scanners come with three different pieces of software: a device driver that
tells the computer how to talk to the scanner; a scan manager program that actually
controls the scanner from the computer (and is where you choose the resolution
and picture type); and a special edition of a graphics program to catalog, print,
and clean up the images you make.
If you change computers, you will want to reinstall the drivers and scan manager
software. Be sure you can hook it up—some PCs don't have the same connections.
This is especially true with SCSI connections.
What's The Genealogy Tie-in?
Converting pictures of family members and images of historic documents to
computer files gives you the option of linking those files to your genealogy
records about those people, and of e-mailing them to your relatives and colleagues.
More About Resolution - PPI, DPI, LPI
If you get a headache from doing a lot of math, skip this section and get
your kids to do your scanning. There are three important points to cover about
resolution:
file sizes,
variations in resolution for cameras, monitors, and printers, and
enlargement.
File sizes can get out of control if you're not careful. A 3"x5" image
scanned at 200 pixels per inch in black and white contains only 600,000 pixels,
and takes up 4.8 million bits. By the time you store it on your hard drive in
JPG format, it might not take more than 25K of disk space. But scan that same
3"x5" image at 300 dots per inch in RGB format (24 bits per pixel
- 8 red, 8 blue, 8 yellow) and you have 32 million bits. Some scanners and printers
boast of 2400 DPI resolution - try that and you'll obtain over 4 billion bits.
Hard disk space is relatively cheap, but unless you're starting an archive or
printing a magazine, you can generally scan at 200 DPI and be happy with the
image.
One of the first things that I had to learn after I acquired a scanner was the
difference in the size of an image when I saw it on the screen and on the printer.
Let's say that you scan a 4"x6" photo at 200 dots per inch. If your
printer has 600 dot per inch capability, and you don't add dots when you print,
the printed image will be one-third the scanned size, or about two inches wide.
Put the same image on a monitor, which has a resolution of about 72 dots per
inch, and you'll see an image about three times as large. The important point
is that knowing where you want to display a scanned image might have an impact
on the size that you scan it - printers and monitors are different enough that
you might find it reasonable to create two different scans.
Enlargement is a great feature of computer images, but one that can trick you.
If you have a 35mm slide, and want to print it out at 1200 dots per inch on
your photo printers, 7 inches wide, you'll need a whole lot of dots. In a case
like this, you might wish for a scanner with 5,000 dot per inch resolution.
What you can do, to make the full page photo of your ancestor's head in a group
photo, is enlarge the image 500 percent, and choose a resolution that is related
to your printer's best quality.
What Should You Do?
Should you scan at a higher resolution than you can print? Some people say
no, as if there were a Moral Imperative to preserve dots. Wait, I'm climbing
on my soapbox. Maybe you should scan higher anyway. Perhaps you will be buying
a new printer someday. Or perhaps you want to save the images for one hundred
years and you don't know what technology will be available then. What you should
do is make your own informed decision about how to make these tools work for
you, the way you want. Period. Okay, off the soapbox.
Link Me Up (More Stars Is Better)
ZDNet Reviews ***
Great product evaluations, tips, and explanations for beginners.
Scanning overview ****
A good explanation of the basics of scanner technology.
Scantips ****
Just like its name, lots of scanning tips, including a method for getting the
best pictures.
PPI, DPI, LPI and Color Depth Unraveled****
A page that offers tips and techniques about resolution.
What Else?
Some scanners support transparency adapters (a backlit replacement for the
scanner cover that lets you scan slides and transparencies, about $150) and
sheet feeders (a mechanical replacement for the scanner cover that lets you
scan a stack of papers, about $150).
Digital cameras are great for taking pictures of people. They're not so good
for making images of documents or old photos because you can't get closer than
a couple of feet and the picture comes out too small. One other function of
scanners is to convert paper documents to text, using a process called Optical
Character Recognition, or OCR.
Next time - graphics file formats.
The RootsWorks series of articles focuses on genealogical applications for
generic technologies. Beau would like to hear from you at sharbrough@rootsworks.com,
but due to the volume of e-mail received, he is unable to answer some e-mail
messages. Please note that he cannot assist you with your individual computer
problems. Visit the RootsWorks website (www.rootsworks.com/
) for links to previous articles and Beau's lecture schedule.
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