Scanners

It's not so long ago that a scanner was such a costly piece of equipment that it was difficult to justify buying one for anything except an absolute need. But scanners are now so much more affordable that their usage has become more wide-spread, and PC owners everywhere are realising that adding a scanner to their existing setup can open up whole new worlds of performance.

Put a scanner with an image editing package for instance and you too can perform the tricks of the electronic photo retoucher. Use a scanner to scan original artwork and you can create the basis for your own designs. Position photos for the newsletter that you edit, or create images for printed documents to feed to your fax/modem card. Or why not organise your collection of magazines by scanning in the pages and using a document indexing and retrieval program. By using an OCR - Optical Character Recognition - package you can even convert printed text into editable word processor files.

There are two main types of scanners that will do the many of the above tasks - hand-held and flatbed. Put simply hand held scanners are cheaper, but flatbed scanners are more convenient. However it isn't necessarily the case that you would always choose to use a flatbed scanner for the job, as for some tasks a handheld may be just as suitable. A flatbed scanner for instance, takes up a lot of space, whilst a hand-held scanner is better at scanning objects that aren't 100% flat!

But let's take a closer look at the two main types of scanner and how they work.

Using a hand-held

A hand-held scanner takes the form of a small scanning head that has to be moved across the original piece of artwork. A small roller under the scanning head rotates as you move the scanner and lets the PC know how fast you are scanning. You have to move at a nice steady rate in as straight a line as you can manage. If you wobble¹ then the input image will contain wig­gles² and distortions. As you scan, image data is sent to your PC as fast as the hardware can cope with it. However the amount of data in an image is so large that it is possible to swamp³ the machine. In simple terms, if you move the scanner too fast then the data will be generated faster than it can be accepted and bits of the image will be missing. How do you know what is too fast? Most scanners either have a light on the scanning head or an on-screen display that provides feedback—slow, fast, too fast.

So using a hand scanner is something of a skill — like driving a toy car down the page while keeping your eye on how fast it should be going. It isn't a difficult skill to master, however, and many users swear by the convenience of the hand scanner for occasional image input. Another factor that you have to keep in mind is that most hand scanners are only four inches wide. To input an original that is wider than this you have to scan more than once and use special software to 'stitch'⁴ the separate strips together. This sounds like a big disadvantage, but in practice it isn't so bad and can even be an advantage because you can run the small scanning head over surfaces that aren't completely flat — e.g. a page in a very thick book.

To Sum Up

hand scanners are

- low cost;

- slightly fiddly to use;

- only able to scan narrow strips which have to be stitched

together;

- but able to scan slightly curved surfaces.

Using a flat bed

A flatbed scanner on the other and works much like a photocopier. You place the original art 1 work on a glass plate, close the cover, and the scanning head moves automatically down he page. All this happens under the control of your PC so there is no need to worry about keeping the scan straight or getting the right speed as in the case of a hand scanner. However the or original still has to be placed squarely on the scanning plate — more difficult than you might imagine — and it has to be as flat as possible. For example if you want to scan a thick book or magazine then it is often better to remove the page in question than to try to flatten it with heavy weights!

The advantage of a flatbed scanner is that once you have placed the original in it. everything happens automatically, you can go away and do something else while a scan is in progress — and a full colour A4 scan can take minutes to complete. You can even get sheet feeder attachments that will allow you to scan in a pile of A4 pages completely automatically. The scanning method is also accurate in the sense that it doesn't rely on how well you move a hand scanner down the original. This allows flatbed scanners to offer a higher resolution than hand scanners — although it has to be admitted that there is a lot of overlap in specified performance.

To Sum Up

flatbed scanners are

• easy to use as long as the original can be placed flat on the scanning plate;

• able to scan large areas in one pass;

• can work at higher resolutions;

• expensive.

(PC R.)

Упражнение 40. Подготовьте краткое описание каждого из известных Вам устройств ввода, отметьте его преимущества и недостатки. Когда и почему целесообразно использовать то или иное устройство?

Output

Упражнение 41.

a) Прочитайте текст, обращая внимание на новые термины: