Image capture

A digital camera takes photos electronically and converts them into digital data (binary codes made up of Is and Os). It doesn't use the film found in a normal camera; instead it has a special light-sensitive silicon chip.

Conventional cameras depend entirely on chemical and mechanical processes -- you don't even need electricity to operate them. All digital cameras have a built-in computer, and all of them record images electronically.

Photographs are stored in the camera's memory before being sent to the computer. Some cameras can be also connected to a printer or a TV set, to make viewing images easier.

Since film still provides better picture quality, digital cameras have not completely replaced conventional cameras. But, as digital imaging technology has improved, digital cameras have rapidly become more popular.

A camcorder, or digital video camera, records moving pictures and converts them into digital data that can be stored and edited by a computer with special video editing software.

Digital video cameras are used by home users to create their own movies, or by professionals in computer art and video conferencing.

They are also used to send live video images via the Internet. Then they are called Web cameras or webcams.

Scanners have become an important part of the home office over the last few years. Scanners are great for archiving old photographs in a digital format that will never fade, converting print documents into digital word processing files that can be edited and even compiling and organizing business cards. At their core, scanners haven't changed much over the years, but they've become much more refined devices, capable of crisp and accurate reproductions.

Scanner technology is everywhere and used in many ways:

· Flatbed scanners, also called desktop scanners, are the most versatile and commonly used scanners. Flatbed and photo scanners used to be separate devices, with the latter being much smaller and offering higher resolution and color depth to handle photographs. However, specifications for flatbed scanners have increased while the cost has stayed the same, and most new photo scanners are simply high-resolution flatbeds.

· Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. Sheet-fed scanners are small models that feed a document or photograph through the thin, compact body of the scanner to capture an image. These are less popular than they were a decade ago, but they're still around. Sheet-fed scanners are more portable, but they don't usually have the same resolution or versatility of the full-size flatbed scanners.

· Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text.

· Drum scanners are used by the publishing industry to capture incredibly detailed images.

· Film scanners are specialized scanners that can accommodate strip film or slides. Generally, film scanners have very high optical resolution, such as 2, 400dpi or greater.

· Speaking of portability, pen scanners have become more prevalent in recent years. These scanners can either scan text one line at a time or, in some of the newer models, scan entire documents or images in a single pass. They're extremely easy to carry around, but you need a steady hand to capture an accurate image.

Scanners vary in resolution and sharpness. Most flatbed scanners have a true hardware resolution of at least 300x300 dots per inch (dpi).

Sharpness depends mainly on the quality of the optics used to make the lens and the brightness of the light source.

Another term used when talking about scanners is bit depth, also called color depth. This simply refers to the number of colors that the scanner is capable of reproducing. Each pixel requires 24 bits to create standard true color and virtually all scanners on the market support this. Many of them offer bit depths of 36 bits (12 bits per primary color). They still only output in 24-bit color, but perform internal processing to select the best possible choice out of the colors available in the increased palette. More sophisticated scanners have 14 bits per color, or 42-bit color depth. Extended color depth is generally more important for photographic scanning or graphic arts work. There are many opinions about whether there is a noticeable difference in quality between 24-, 30-, 36-, and 42-bit scanners.

Scanning the document is only one part of the process. For the scanned image to be useful, it must be transferred to your computer. The connections used by scanners:

· Universal Serial Bus (USB) - USB scanners combine good speed, ease of use and affordability in a single package.

· FireWire - Usually found on higher-end scanners, FireWire connections are faster than USB and SCSI. FireWire is ideal for scanning high-resolution images.

On your computer, you need software, called a driver, that knows how to communicate with the scanner. Most scanners speak a common language, TWAIN. The TWAIN driver acts as an interpreter between any application that supports the TWAIN standard and the scanner. This means that the application does not need to know the specific details of the scanner in order to access it directly. For example, you can choose to acquire an image from the scanner from within Adobe Photoshop because Photoshop supports the TWAIN standard.

In addition to the driver, most scanners come with other software. Typically, a scanning utility and some type of image editing application are included.

A lot of scanners include OCR software. OCR allows you to scan in words from a document and convert them into computer-based text. It uses an averaging process to determine what the shape of a character is and match it to the correct letter or number. OCR software is now readily available for many low cost scanners giving good recognition rates.

One thing to keep in mind with scanners is that creating high-resolution scans consumes a lot of resources, including hard drive space. If you're going to be scanning numerous full-size images, make sure you've got a computer with the power and the space to handle them.