- The dictionary defines a digital scanner as "an electronic device that generates a digital representation of an image for data input to a computer." More simply, the scanner takes a picture of a tangible document, which could be a photograph or any printed sheet, and breaks it into a series of pixels. Pixels are the smallest computer dots that combine to present an image. A pixel is to an image as an atom is to matter.
- It helps to understand the difference between digital and analog technologies. In the digital realm, everything is broken down into pixels placed on a graph. Every image is nothing more than a series of dots. Here's a good analogy: Look closely at a newspaper photo, and you see a series of dots. Look closely at a true photograph, and there are no dots. The same is true when comparing digital and analog technologies. The digital scanner is the device that converts analog images into dots. Once an image is converted to digital, endless reproduction and computer manipulation of it is possible.
- Flatbed scanners have a platen (or glass plate) that holds the photo or sheet. The scanner then passes under it recording the image and breaking it into pixels. The item being scanned remains stationary. In sheet-fed equipment, the scanner remains stationary and the photo or document passes over it. Each type has its pros and cons. Flatbed scanners produce better quality scans; however, the scan size is limited to the size of the glass. Most flatbed scanners cannot handle photos or documents larger than tabloid size. Sheet-fed devices can scan larger images; however, they cannot be used for photos or documents that are thick or fragile as those originals cannot pass through the scanner's feeding system.
- As with all digital equipment, the higher the resolution, the larger the file. The same is true of digital scanners. The measurement reference of resolution is either dpi (dots per inch) or ppi (pixels per inch). A scanner that is specified to have a resolution of 4800 x 9600 means it scans 4,800 dots horizontally and 9,600 vertically. Most manufacturers use the first number in the resolution specification as the overall reference. Digital scanners with resolutions above 4800 dpi render the best quality for photographs. Scanners with a 2400 dpi are all-purpose devices, and those with 600 dpi are designed to scan documents only. The 600 dpi resolution is completely adequate for scanning typed pages.
- The scanner's ability to capture colors is defined by its bit depth. Higher bit depth translates to broader color representation. A scanner with 24-bit color is the most basic type. If you want to scan photographs, a 48-bit scanner is better. With the higher bit depth, the scanner has the capability of capturing more of the tones and gradations of any color that exist in photographs. A scanner with 96-bit color is the right choice for scanning original artwork or paintings as these have the widest array of colors. Although you can manipulate scanned images in a number of programs, it's always best to scan at the proper resolution and bit depth to start.
- The most important consideration in scanner selection is your end use. Scanner prices are based on resolution, bit depth, speed and software features. In the case of digital scanners, more expensive does not necessarily equate to better. There are a number of models available that offer resolution quality that is adequate for most applications. Depending on your end use, more resolution isn't noticeable (i.e.; web viewing) and only serves to create a larger file than you need. If the final output is a quality poster, then higher resolution scanning is needed. Digital scanners range from under $100 to over $2,000.
