AdminXP.com: Scanner and insertion image in the computer

Scanner and insertion image in the computer

Use

For insertion photographs, books and other documents in the computer. Following use in Internet pages, graphic items for advertising materials, family albums or sending to friends through email.

Principle

Similar to photocopier. Under the glass plate on which a document is laid a bright light lamp goes through. Intensity of the reflected light is converted into digital form by help of sensing element.

Kinds of scanners

By type

Hand-held scanners

The scanner moves over the scanned surface. Very low quality and speed. Black and white only.
For very small surfaces, rescanning and successive folding together is generally necessary, though, the result is not too quality.

Edge-fed scanners

Sheet of paper goes through the scanner. Disadvantage: not possible to scan books and thick documents. The principle is similar to fax (there is an easy built-in edge-fed scanner in the fax).
Lower quality and speed. Comparatively high price. (A typical example is the scanner built in the HP 1100A printer, this scanner is black and white and its price is comparable with a color desk scanner enabling books scanning).
For common office documents.

Desk scanners (Flatbed)

Sheet of paper or a book is laid on the glass plate.
High quality and speed for a good price.
Some producers add other devices to scanners, e. g. extension for photographic slides or paper feeder for automatic scanning of several documents quickly one after another. Though, the slides extensions do not provide high quality and it is recommended to use professional scanners for photographic slides

Multifunctional scanners

Scanners combining several devices, generally scanner and printer. So the device can be used for several purposes - scanner, printer, copier. Advantage: saving of space in small offices.
Disadvantage: "unlucky" combination of scanner and ink printer often used as photocopier. Higher print costs when printing several hundreds of copies, it would be certainly more worthy to invest rather into a laser printer and common scanner.

Special

3D - Special and expensive scanners allowing to input a 3D model of the scanned object in the computer.
Drum scanner - For film studios and firms specializing on graphic. Scanners for special use - photographic slides and film, large surfaces.
Scanner for bar codes - Scanner for scanning bar codes from the goods.

By connection

Parallel - Slower connection through printer port; cheaper. Suitable for home and common use in office. Most of the parallel scanners have also LPT plug-in for printer, so it is not necessary to connect and disconnect printer or scanner.
USB - Fast connection almost reaching SCSI speed. Connection through USB port; cheap.
Suitable for demanding users and professional use. Older computers do not have USB port! Note weaker support for Windows 95SR2 and no support for Windows NT 4.0.
SCSI - Very fast connection through SCSI interface. More expensive, designed for professional use.
Firewire (IEEE1394) - New high speed interface - Probably, you will not find it on you computer, for the present special cards are added to scanners to be able to get connected to computer. This interface is often used for connection of digital cameras.

Parameters

Dpi (Dots per inch) - Value defining scanner resolution. The higher value the more precise scanned image. 300 - 600Dpi usually serve for common work. Most of common scanners have 600 x 1200dpi in optical resolution. Distinguish Optical and Software resolution. Software resolution can be several times higher than the Optical one. In the software resolution some elements are specified by computer.
One pass - Primary color spectrums are sensed at once. Fast scanning
Multiple pass - The color spectrums are sensed in sequence. Multiple pass scanners are slower but more precise. Most frequently you can see 3-průchodovými - the primary colors (RGB - Red, Green, Blue) spectrum is sensed.
CIS - Contact Image Sensor - Based on two lines of diodes - 1. high light, 2. sensing diodes - In comparison with CCD technology the optical elements are not necessary here. For users it means lesser proportions, higher resistance and lower price. Disadvantage: lesser intensity of light and sensitivity. Not designed for photographic slides and professional work
CCD - Charge Coupled Device - Based on high light lamp and optical system. Disadvantage: lower resistance and higher price. Advantage: higher intensity of light and sensitivity. Possible to use also for photographic slides and according to other parameters for professional work.
Color depth - Number of colors which the computer can recognize. The most frequent is 24 and 48bit. In case of 24bit you can also hear the expression True Colors - 16,7mil colors..

Computer requirements

Parameters of your computer. For frequent scanning of photographs you need a computer with higher RAM memory, large harddisk and fast processor. Present minimum standard for good work is 400Mhz CPU, 64MB RAM and large harddisk (5 and more GB). For professional work 600MHz and 128MB RAM is minimum.
Find out which operating system you use. Some scanners support only some of the operating systems. E. g. USB scanners can work in Windows NT 4.0 only with large difficulties and for some of the older you will miss support and drivers for Windows 2000.
Find out the type of connection that can be used in your computer. - Probably parallel or USB. But as mentioned earlier some computers do not have USB.
More advice you should get from your seller (visit several shops and you will see).

Time and memory demand for scanning

16x19cm

dpi	čas	MB
150	30s	3.42
200	33s	5.91
300	58s	13
400	1m 4s	23
600	2m 20s	51.4
800	2m 50s	91.3
1200	4m 05s	205
1800	7m 48s	461

Different formats

TIFF	BMP	JPG	GIF (256barev)
13.0 MB	12.8 MB	3.28	1.65

When it does not work with scanner...

For bigger pictures or larger surfaces use camera, you can later transfer the photograph using scanner. For those who want to skip the time consuming procedure of photographs development, I recommend to use digital camera. The lower price cameras provide lower quality, however, the price is still high. In case of frequent photographing and transferring to computer the digital camera is really necessary. The costs return very fast. Bad photography you can simply delete and make them again.
For moving pictures use video camera and transfer the image to the computer using card with video input. Some cameras have firewire input, without the necessity of using the card with video input.

Beware of scanner damage!

There belong no heavy things on the glass, it could get broken!
Some scanners have a fuse to ensure the scanner in case you want to travel with it. The movable part with sensing element is put in stable position, so the risk of possible sensing element damage is lower. When you turn the scanner on you have to turn the fuse off or you risk scanner damage.

The more expensive the better?

It is not always so. Producer brand, parameters, type of connection and sometimes also supplied software are decisive. A part of the more expensive types can be some of the professional graphic programs for better price.

Software supplied with scanner

Programs for scanning - Parameters settings and following storage in a file
OCR (Optical Character Recognition) - Transferring texts into text format. You can transfer a scanned picture containing text to text format. Even if the information about easy transfer of texts can be an impulse to change your secretary, it is not a good idea. Also the best programs have some per cent of error rate and the transferred documents must be corrected. Czech characters or some kinds of fonts remain a problem. Probably the best known product is Recognita.
Graphic programs - Programs for further adjustment of scanned images (Adobe Photoshop, Corel Draw...)