Exploring Equipment: Scanner

Section 6 Exploring equipment

Exploring equipment: Scanner

At its most basic level, a scanner is just another input device, like a keyboard or a mouse, except that it takes its input in graphical format. These inputs could be photographs for retouching, correction, for use in desktop publishing or for use in learning resource creation. They could be hand-drawn images to be added to documents, or pages of text that suitable Optical Character Recognition (OCR) software can read and save as an editable text file. They could also be three-dimensional objects, such as coins, provided the object does not have too much depth.

The majority of scanners connect to the computer using a USB port, and there are many different scanners to choose from, with the most popular type being a flatbed scanner.

The flatbed scanner is similar to a photocopying machine, in that it has a glass plate under a lid, and a moving light that scans across under it, but instead of producing of the image on paper, a digital image is produced that can be further manipulated, incorporated into other files, or simply printed out.

Software, called a TWAIN driver, is required to operate the scanner. TWAIN is a software standard that all scanner manufacturers use, enabling all image-manipulation programs, such as Adobe® Photoshop® or Jasc® Paint Shop Pro™, to operate all scanners. Each manufacturer provides its own TWAIN driver for its own scanner. You can use the scanner with any image-manipulation program, but you must use the TWAIN driver provided with the scanner. Some scanner software can also operate as a stand-alone program and there will sometimes be a Scanner icon on the Windows® toolbar following installation. The TWAIN driver will always have another name too, for example, Microtek’s is called ScanWizard, Umax has two, called VistaScan and MagicScan.

The TWAIN driver provides the controls used to specify the requirements of the scan: the mode (colour, black and white, or line art), the resolution (72 or 300dpi) and the area to be scanned. There are also controls to help correct the tonal quality and colour balance of the item to be scanned, and some scanners will also have settings to specify the item being scanned is for facsimile transfer or just a straight copy for printing. If you access the scanner via an image-manipulation program, the scanned item will be transferred automatically to that program where it can be further improved on.

Resolution

The resolution at which you set your scanner for each item will depend on your required output mode, which will normally be either the monitor or the printer.

For using the scanned item on the monitor, the scan resolution simply determines the size of the image. If you scan a 4” item at 200dpi, or a 2” item at 400dpi, you will create an image displayed on the monitor at 800dpi. So the important point is to set the scan resolution to produce the required size depending on the resolution you have your monitor set at. For example: if you are running your monitor at a resolution of 800 x 600ppi (pixels per inch) and you are scanning in a photograph which is 6 x 4”, that you wish to fill the screen with, then you would use a scanning resolution of 140dpi:

(6” x 140dpi) x (4” x 140dpi) = 840 x 560ppi

If you are running your monitor at a resolution of 1024 x 768ppi and you are scanning the same photograph, then you would use a scanning resolution of 180dpi:

(6” x 180dpi) x (4” x 180dpi) = 1080 x 720ppi

So it is important to know the size of the area of the item you are scanning in inches and the size you wish the image to appear on your monitor in pixels, so that you can adjust the scanning resolution to achieve this.

On the monitor, resolution determines image size, not quality. Printing is the opposite: resolution does not determine image size on the printer. The majority of image-manipulation programs, such as Adobe® Photoshop or Jasc Paint Shop Pro, print the scanned images at the same size as the scanned item. For example, a scanned 6 x 4” photograph will be printed as 6 x 4” on paper. The size of the original scan area determines the printed image size. Using a higher scan resolution may make the image look clearer, but the printed size will be the same regardless. If you are scanning for print, then the resolution you scan the image at will be the maximum resolution your printer is specified to handle. Generally speaking, most inkjet printers will produce good results for photographic images scanned at 200 – 300ppi. Graphic images, including text, will require a higher resolution of 300ppi, and line art will require 600ppi.

File formats

The most common file formats to save your scanned images are TIFF, JPEG and GIF.

TIFF will give you the best quality but the largest file size. It is commonly used in commercial printing and professional environments. JPEG, GIF and PNG are all used for images to be included on a web page. Browsers can only recognise these file formats. JPEG is the most popular choice for photographic images and GIF is the most popular choice for graphic images. JPEG will give you the smallest file size and is ideal for sending images by email.

Computer specification for running a scanner

IBM-compatible Pentium® 150MHz processor
48Mb RAM (128Mb recommended)
Windows NT 4.0, 98SE or later
100Mb free hard disk space
CD-ROM drive
Available USB port

Macintosh®:

Mac OS 9+, G3, G4
64Mb RAM
300Mb free hard disk space
CD-ROM drive
FireWire port

Note: if you are going to be scanning and saving a lot of photographs, you will need to ensure you have adequate disk space for storage.

Further information

The HardwareCentral website [
The Ideal website offers a comparison option [
The DealTime website offers a price guide and comparison option [

E-Guides training programme