Scanning and graphics manipulation is one
of the most misunderstood elements in
computing. Getting your scanner up and
running is only the beginning and if
you don't understand some basics about digital
imaging you will be pulling your
hair out in no time. First some things
you need to know about digital images:
DPI: Dots per Inch is what the name suggests,
the quantity of dots of color per inch,
and is most frequently referred to as RESOLUTION.
Most people assume that the more dots per inch,
the better the picture will look. That is true.....
sort of. The problem is, it all depends on what
you are using to view the picture. If you are going
to just look at it on the computer monitor then every
dot per inch above 72 is wasted. Your monitor only
shows 72 dpi and every dot above that is doing nothing
more than adding to the size of the file without adding
one iota of quality. If you are printing the picture
then generally 200 to 300 is about the max, depending on
the printer and the way you have it set up. But,
for most printers, 200 is about the best you are going
to do. Some scanning software doesn't even address the
issue of DPI unless you dig way into the settings.
Instead it will ask you what your PATH is, meaning, where
are you going to end up using the picture. It will
give you a choice of the "screen" or a whole listing
of "printers." But, if yours asks you to enter the
DPI then remember that 75 or so is good for the
monitor and 200 is good for most printers.
SCALING: Sometimes your scanning software will
substitute the term "Percentage" for "Scaling."
This is simply how big you want to blow up the picture,
with the original being the starting point. A 3.5 X 5 inch
photograph scaled to 200 (or 200%) will show on your monitor
as a 7X10. So, before you scan determine what size you want
the final image to be. Consider that you may not scan the entire
image, either. More about that later.
BUT: Here is where it can get a little complicated. If you
scale a picture to 100% and scan it at 72 DPI it will appear
the exact same size as the original on your computer screen.
If you scan it at 100% but increase the DPI to 144
(double the DPI) it will appear twice as big on your monitor,
but will print to it's normal size on a printer that prints
at about 150 DPI or greater. What you are seeing on the
monitor is the screen trying to show you all the Dots Per
Inch you asked for. Since it can't cram any more
than 72 dots per inch on the glass screen it simply blows
it up. This isn't important to you except to keep you
from getting very confused because a picture is much bigger
on the monitor than you expected.
ANOTHER COMPLICATION: Sometimes, when you are printing
a picture the computer will ask you what size you want
it to be. Don't think you can just take a picture you
scanned at 5X7 and make it 8X10. It will print it that
big alright, but it will lookterrible. Always print to
the size you scanned (or smaller). If you want the print
to come out 8X10 on paper then set your scale or percentage
to a number that will make the final scan 8X10.
COLORS: To make it as simple as possible. I recommend
you scan all pictures, either black and white or color,
in the best possible color setting, which is usually called
"millions of Colors." Scan B/W documents in "line art."
This is not a hard and fast rule and you can experiment
with the document scans. Sometimes documents look better
when scanned as gray scales. But, if you are going to
convert a scanned document to word processor text, commonly
called Optical Character Recognition (OCR), then you need
to scan it as line art.
SCANNING: All scanner software comes with two-step
scanning. The first is called the preview or initial
scan. The scanner scans everything on the platen. This
is only the first step. The next step is to select
what portion appears on the platen that you want to scan,
and scan only that portion. This is very important.
When you put the mouse pointer over the picture it will
become a cross hairs. Put the mouse in the upper left
corner of where you want to crop (actually, any corner
will do) then, holding down the left mouse button drag
the cross hairs to the furthest corner from where you started.
When you let go there will be a box around what you want to
scan. If you don't like the cropping you can start over,
or you can just put the cursor on any of the four sides and
adjust the box. Then hit FINAL or whatever your scanning
software calls the last step. The software will pop up
and ask you what you want to call the picture and where you
want to store it on your hard drive. Give it a name, find
a place for it, and hit FINAL. This two stage process is
standard, but the methods and names used by different
software packages varies greatly. Some even have
automated systems that are SUPPOSED to make it all very
easy. Read your manual.
FILE FORMATS. This can get very, very complicated so I
will try and reduce it to what you need to know. Most
scanners limit the kind of format you can create when you scan
a picture. Format is the three letters after the name of
the file, for instance: mypicture.tif or mypicture.bmp .
Tif is Tagged Image Format, and BMP is Bitmap. The three
letters at the end of every single file in your computer
is often referred to as the EXTENSION and simply tells
the computer how to handle the file. Both of these
formats (tif and bmp) will show your pictures at their
very best, but at a huge cost in drive space. A 5X7
picture scanned in millions of colors can use anywhere from 3
to 5 megs of space on your hard drive. It's not hard to
see that if you scan a lot of pictures and forget about
them you will eventually use up most of your hard drive.
But, you've got to scan them as something and since
your scanner won't give you too many choices you
can pick either one. There is a difference in the
two formats but for our purposes the differences are
not important. Pick one and stick with it. I
suggest TIF. Also, create a folder on your hard
drive for your initial scans and always put your
Ok, you've scanned a picture called myhouse.tif
and saved it to a folder on your hard drive called
familypictures, so the path to the folder would be
Now, what do you want to do with the picture? If
you want to print it, just open up your graphics
program, bring up the picture, and print it. That's
all there is to it, unless you need to fix or clean
up the picture. That is a function of the kind of
graphic program you use and I won't discuss that here.
What if you want to e-mail the picture to someone? You
could e-mail it as is (myhouse.tif), but the person you
are sending it to will not be happy receiving a huge
file that will most likely take an hour to download.
So, the next step is to convert it to a file format that
is more efficient for e-mailing and screen viewing.
The standard is JPG and is what you will see most often
on web sites. On the screen a JPG and a TIF or BMP
will look exactly the same, but the JPG, because of efficient
data compression, is a much smaller file. A 5 meg
TIF can be reduced to a 35K JPG file. It won't print
worth a damn, but it looks just as good on the screen (all things
being equal, and I will get into that next).
The easiest way to convert a file from a TIF to a
JPG is to use the software that came with your scanner.
These days most scanner software includes a little wizard
that will take a picture and process it for e-mail.
It will reduce the resolution to 72 DPI and change
the picture to a JPG. If not, you can just have the picture
open in your graphics program and do a SAVE AS.
You can keep the same name, but change the extension to JPG.
If you have already scanned it at 72 dpi, you will be
ready to mail it.
ONE SMALL BUT IMPORTANT DETAIL: JPG can be saved as a
specific quality. The quality scale is sometimes 1 to
100 but I have seen it rated at 1 to 200. In any case,
there is not a noticeable bit of difference between the very best quality
and a few numbers less, but the file size is very different.
You will need to experiment on what you find acceptable in
the final product, as a trade off for file size. If you
saved it as a 20 quality your file size would be 1 or 2K. It
would zip through the e-mail at the speed of light, and look
horrible. Usually, 90 in the 1 to 100 scale is about the right level.
Anyway, that's about all there is to it, except for a
lot of stuff that is of great concern to layout artists and
web production people. To us folks who just want to
e-mail pictures around, the rest doesn't matter much.