Many home computing work
stations are now sold with a flatbed scanner, which in conjunction with
a printer and fax software, can be used as photocopier and fax machine.
But most people are more interested in scanning their favourite photographs
to copy and email to friends.
The most important thing to note is that the quality from a scanned
image will never be the same as the original. Its like the photocopying
machine .... each successive generation degrades the image. The only
way to get the original quality of a photographic image is to find the
negative.
1) Resolution
Scanning is much like photocopying, but you have more choices as to
what to do with the output. For emailing you only need a small low quality
image, whereas for photo reproduction you need as much information as
you can get. The human eye can really only see about 200-250 dots per
inch, but the scanner will usually default to about 150dpi which is
a reasonable quality for faxing and draft copying.
If you want to enlarge a photo, the rule of thumb says that you can't
enlarge it more than twice its original size without serious loss of
quality. Basically when you double the size you halve the resolution
(400 dpi becomes 200dpi).
The following is a table to help you set the scanner to the correct
resolution for your need:
Email: 72 (dpi)
Photocopy / Fax: 150 (dpi)
Human eye: 200-250 (dpi)
Maximum (for enlargements) 400 (dpi)
2) File Types
Most scanners have a quick button on the front that works much like
a photocopier. Put the photograph on the scanning surface and push the
button. Using this method you will probably end up with a bitmap of
low resolution.
A bitmap is a raw file that has not been compressed,
but will not degrade with successive modifications and saves.
For most uses a JPEG file is the best choice when saving your scan.
It is compressed, which means it will be easier to store and to email.
As a guideline level 8 compression (medium/high quality) will mean that
there is no visible loss of quality due to the compression. A JPG file
will be anything from 20% to 5% of the size of the raw bitmap file,
so its worth doing!!!
3) Quality
It is possible to get a good copy of a photograph, but it will depend
on the quality of the original photograph. You can improve the quality
of the ouput, by using the following tips;
Make sure the glass surface of the scanner is clean. It very quickly
gets dusty and smeary. Get out the glass cleaner and give it a really
good polish before starting.
Make sure the item you are scanning is as straight and flat as possible.
Select the correct resolution for your intended end use.
Crop the image to remove unwanted borders, edges or anything else that
degrades the photograph. Use either the scanning software or other image
editing software.
If you have image editing software, "auto level" or "auto
correct" the image. This will boost the contrast and saturation,
to be far more like the original image.
That's it! Have fun scanning your favourite photos !!!
