Ascanner lets you transfer printed images, whether photos or printed text, into the computer as digital images. The most common type of scanner looks like a copier with a glass surface where you place the scanned document, and a button to initiate the scanning process. Scanners are typically connected to a computer with a USB cable.
On the computer side is the Scanner and Camera Wizard that lets you preview the document before starting the process. You can also select to scan the document as a color photograph or as a black-and-white page of text.
Using additional software, you can process scanned pages of text and convert them into text documents that can be edited just like any other text document.
When looking for a scanner, keep in mind why you need it. Do you need to archive your old photos onto CD, do you need to scan hundreds of images for a home business catalog, or do you need to convert pages of type to editable documents? A wide range of scanners is available on the market from very expensive to fairly reasonable depending on intended use.
The most common home scanner is the flatbed scanner. This type of scanner is like a small copier with a glass plane where the object to be scanned rests. Once the scanning process starts, a light sweeps across the range of the page and sensors detect the image.
All-in-One printers, covered in Chapter 35, can also scan documents.
For portable systems, you can get a handheld scanner that is much smaller than the flatbed and works by dragging the device over the page.
Handheld scanners can be problematic because they rely on the user dragging the scanner smoothly across the page for a good scan.
Flatbed scanners can be outfitted with a document-handling unit that enables multiple pages to be scanned without manually placing each individual page. An alternative to getting a document-handling unit is to purchase a sheet-fed scanner that has document-handling hardware built into the scanner.
Slide scanners are specialized scanners that can scan images from film negatives and slides.
Print shops and pre-press departments typically use a drum scanner that can scan images at very high resolutions, but can also be very expensive. Other expensive specialized scanners include microfilm and slide scanners that can scan rolls of film and transparent slides.
The most common flatbed scanner size is letter-sized, which can scan a normal 8.5 × 11–inch page. Larger scanners that can handle legal-sized documents are also available.
Another distinguishing feature of scanners is the resolution that they are capable of scanning. Images intended for display on a computer monitor, such as those that appear on Web pages, can be scanned at 72 dots per inch (dpi). This resolution is fairly low and should be handled by most scanners. Images for print should be scanned at 300 dpi. Scanners that are capable of scanning at higher resolutions can capture finer detail.
The maximum resolution capability is determined by the scanner's optical scan resolution value, which can range between 1200 × 1200 to 4800 × 9600 for higher-end scanners. The optical scan resolution is the actual number of dots per inch that can be scanned. Many scanners report higher resolution values as interpolated scan solution, which is the number of dots per inch that can be computed.
Scanners also report the number of bits that the scanner can process. This value is the amount of scanned data that is captured by the scanner. Larger bit depths can produce larger data files with more resolution. A 24-bit scanner produces files with half the resolution of a 48-bit scanner.
Most scanners use one of two technologies-Charge Coupled Device (CCD) or Contact Image Sensor (CIS)-to produce a scan. CIS technology is newer and works by converting light into electric signals that can be used to create a digital image. CIS scanners are generally smaller and more compact that CCD scanners and require less power.
Another major factor that influences the scanner cost is the software that is bundled with the scanner. Most scanners come with software that allows users to edit images and to convert scanned text to editable text. The software that allows scanned text to be converted to editable text is called Optical Character Recognition (OCR) software. Less expensive scanners are typically bundled with "light" versions of software, and more expensive scanners include full versions of software.