Post image processing rarely involves more than a good photo dedicated printer. There may be times when you would like to repair or improve some old photos where you would also need the use of a good high resolution digital scanner.

Digital Scanners:

In computing terms, a scanner is an electronic device that ‘scans’ images, printed text, handwriting, or an object, or pretty much anything you care to throw at it (as long as it fits inn the machine) and converts it to a digital image in a variety of different image file types. The most common examples are of the ‘flatbed’ type.

A flatbed scanner more often than not comprises a ‘platen’ (glass pane) under which there is a bright light (often xenon or cold cathode fluorescent) which illuminates the pane, and a moving optical CCD scanning array. CCD-type scanners typically contain three rows (arrays) of sensors with red, green, and blue filters. CIS scanning consists of a moving set of red, green and blue LEDs with a connected monochromatic photodiode array for light collection. Items requiring scanning are placed face down on the glass & an opaque cover is lowered over it to exclude ambient light. Once the ‘go’ button is depressed, the sensor array and light source move underneath across the platen & scans the entire (or pre-selected) area. The scanned image is created from the information that the ‘collector’ receives i.e. it records exactly how much light is reflected of the subject surface & processes that information using complicated algorithims to ‘even out’ the image. Transparent images do not work in this way in that they require special accessories that illuminate them from the upper side. Some highe end scanners offer this as an option.

Modern scanners typically use a charge-coupled device (CCD). ‘Contact Image Sensordrum type scanners utilise a ‘photomultiplier tube’ as the imaging sensor. Planetary & Rotary scanners (used to scan books and documents) are mainly used in libraries or that of environment. There is also, although still in it’s infancy (but is available on the market) a range of 3D scanners which produce 3D models of objects (Google these – mind boggling!).

Another category of scanner is good oled digital camera. These are simply based on the concept of reprographic cameras. Due to ever increasing technology of camera & high resolution sensors plus new features such as anti-vibration, digital cameras have become an attractive alternative to regular scanners. While they still having disadvantages compared to traditional scanners (such as distortion, reflections, shadows, low contrast), digital cameras offer advantages such as speed, portability and gentle digitizing of thick documents without damaging the book spine. New scanning technologies are combining 3D scanners with digital cameras to create full-color, photo-realistic 3D models of objects.

Printers:

Printers are normally named by the technology used in their coonstruction. A lot of different technologies have been developed over the years. The type of printing ‘engine’ has a critical effect on what types of tasks a printer is suitable for due to different technologies that are capable of producing different levels of print finish i.e. image/text etc.

Another aspect of printer technology that is often overlooked is ‘alteration resistance’. Liquid ink, such as that used in inkjet head or fabric ribbon type printers, is absorbed by the fibers of the paper being printed on, so, documents printed with a liquid ink printer are more difficult to alter than those printed with toner or solid type inks, which incidently do not penetrate below the surface of the paper.

Modern types of printers are generally of the following technology:

Laser: Also known as ‘toner’ printers. A laser printer can very quickly produce high quality text and graphics. As with multifunction printers (MFPs) & digital photocopiers, laser printers use a ‘xerographic’ type printing process however the main difference with analog photocopiers is that the image is produced by the use of a laser beam scanning across the printer’s ‘photoreceptor’.

An LED printer is also a variety of a toner pronter. This type uses an LED array instead of a laser to cause toner adhesion to the print drum.

Liquid inkjet printers: Inkjet printers operate by propelling variable sizes droplets of liquid ink onto almost any sized page. They are by far the most common type of computer printer used by consumers these days.

Solid ink printers: (also known as phase-change printers), are ‘thermal transfer’ type printer. As their name suggest, they use solid sticks of CMYK-coloured ink of similar consistency to a wax candle. These sticks are melted and put through a piezo crystal type print-head. The print-head distributes the ink by spraying onto an oil covered rotating drum. The paper is then passed across & over the printing drum, at which time the image is or transfixed (transferred) to the paper medium. Solid ink printers are mostly found employed as colour office printers as they produce excellent results on transparencies and other non-porous media. Purchase and operation costs are similar to that of laser printers. The disadvantages of solid ink technology are high electricity usage and prolonged warm-up times. Also, in some cases, the finished prints are difficult to write on because typically the waxed ink repels pen ink & because of the ‘dried wax’ effect the prints are sometimes difficult to feed through automatic feeders. It should be noted that these issues are subject to continuous improvement & have reduced significantly in more recent models. Another quite major downfall is that this type of printer is only available from one manufacturer, Xerox from their Xerox Phaser range.