What is scanner and its types.
Part of the Printers glossary:
A scanner is a device that captures images from photographic prints, posters, magazine pages, and similar sources for computer editing and display. Scanners come in hand-held, feed-in, and flatbed types and for scanning black-and-white only, or color. Very high resolution scanners are used for scanning for high-resolution printing, but lower resolution scanners are adequate for capturing images for computer display. Scanners usually come with software, such as Adobe's Photoshop product, that lets you resize and otherwise modify a captured image.
Types of Scanner
There are a few different kinds of scanners and, as with printers , the one that’s right for you depends on how you intend to use it. The most common types are flatbed scanners, sheetfed scanners, photo scanner s, and portable scanner s.
Flatbed Scanners
Flatbed scanners will take up some desktop space but provide a lot of bang for the buck. They look like miniature printers with a flip-up cover protecting the glass platen. Depending on its size, a flatbed scanner can fit standard or legal-sized documents, and the flexible cover allows you to scan large items such as books. These scanners are great for scanning the occasional newspaper article, book chapter, or photograph; or for those who may need to scan or bulky items such as the cover of a DVD. Flatbed scanners are often built intomultifunction printers (MFPs). You can find a decent flatbed scanner for $100 or less.
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Photo Scanners
Scanning documents doesn’t require high resolution or color depth ; but scanning photos does. Many all-purpose scanners can also scan photos, meaning that you don’t need a separate device to handle your photographs. But if you need a scanner primarily to digitize film negatives or slides, a photo scanner is a better deal (even if it is considerably more expensive than an all-purpose scanner). Photo scanners include specialized technology so that they can deal with slides and negatives; they also have built-in software to clean up old photos. Decent photo scanners will start at about $130 (and go way up from there). Here are my Top Picks .Sheetfed Scanners
Sheetfed scanners are smaller than flatbed scanners; as the name implies, you feed a document or photo into the scanner rather than place it on top. You’ll win back some of that desktop space with a sheetfed scanner but you may sacrifice some resolution in the process. If you’re only scanning documents, however, it may be a worthwhile trade, especially if you’ve got a lot of them since you can feed them in bunches. With a flatbed scanner, you’ll have to scan one page at a time (unless it comes with an automatic document feeder). Sheetfed scanners start around $300.
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Portable Scanners
Portable scanners are small enough to bring on the road. In fact, some are small enough to put in your pocket; pen scanners are just a bit bigger than fountain pens and can scan the text of a document line by line. Some are as wide as a page and roll easily down the page. They’re not going to give high-resolution scans and so aren’t good for scanning photographs or other applications where you need a high-quality result. Since they’re not cheaper than flatbed scanners, they’re probably only useful if you are a student, a researcher, or a spy. Figure on spending about $150 for one.
Handheld Scanners
Hand scanners are useful for their portability and low price (often one-third to a quarter of the cost of a flatbed scanner). Hand scanners generally plug into a computer's printing port, as opposed to a SCSI port, allowing them to be easily shared from workstation to workstation. Many people find them ideal for use with a notebook or laptop. Unfortunately, hand scanners are less accurate than flatbeds because they have weaker light sources and often produce uneven scans - courtesy of the unsteadiness of your hand or the surface you're standing on. Many hand scanners now offer an alignment template to help guide you when scanning. At least one manufacturer ships a motorized "self-propelled" unit to help stabilize its scanner.
High-end hand scanners offer 400 spi resolution and 24-bit color - allowing you to achieve reasonably high-quality results. But their 4" to 5" wide scan head forces you to make multiple passes to scan even average-sized documents. You'll need to use the supplied stitching software to merge these partial scans back together again - a time consuming task. Nonetheless, hand scanners are very popular and are capable of high-quality, quick and easy, low-cost scans.
Drum Scanners
Professional color trade shops wouldn't think of using anything less than a drum scanner for producing color separations for high-end printing. Instead of using CCD technology, drum scanners use PMT (Photo Multiplier Tube) technology for greater dynamic range and color accuracy. They also cost an arm and a leg, Nevertheless, drum scanners offer features not available to desktop scanners such as direct conversion to CMYK, auto sharpening, batch scanning, greater dynamic range, and huge image scanning areas. Ironically, most drum scanners don"t support preview mode - drum scanner operators are more interested in numbers than what the see with their eyes. Yet what truly sets drum scanners apart is their increased productivity. Since the process of scanning to CMYK is automated, drum scanners can produce more scans per hour than a desktop unit.
Digital Cameras
Digital cameras allow you to shoot three-dimensional objects, much like a regular camera, except you don"t have to wait for film developing and processing. Portable units are presently limited in storage and image size. Studio-only units offer larger image size and dynamic range, but require attachment to a host computer - hardly a portable solution. In the future, high-resolution, high-quality, portable units will surely come--they just aren't here now.
Previous incarnations of "digital" cameras weren't really digital - they digitally sampled the analog signal from a CCD as opposed to converting it to digital data. The resulting data was then stored on floppy disk. The floppy disk then had to be read by a special reader which converted the digital data back into an analog signal which then had to be re-digitized again using a video digitizer (see above) - what a mess!! As you might suspect, the quality wasn't much to write home about, either.
Newer entry-level digital cameras, like Apple's QuickTake, are truly digital, i.e. they keep the signal (nearly) purely digital all the way from the CCD, to the floppy disk, to the computer. The secret is that they use massive compression of the digital data to get it all to fit on a floppy disk. Typically, these devices save from 7 to 32 "frames" of digital data at up to 640x480 resolution, and 24-bit depth. The quality is quite good - good enough for small (i.e. 2.5" x 3.5") reproductions in print, and certainly good enough for many multimedia purposes.
More expensive mid-level digital cameras such as Kodak's DCS 200 use higher resolution CCD arrays (1024x1600) and high-capacity micro hard disks to store all that data. The DCS 200 also uses compression to squeeze all that data onto the hard disk. Optional features include digital modems for sending the images back to a "home" office.
High-end digital backs, such as the Leaf Digital Back (for Hasselblad and Mamiya), use even higher resolution CCDs (2000x2000 or more), higher bit depth (12-bits/sample), higher dynamic range, no compression, and high-speed cables to connect the device directly to a computer, where the image is stored and manipulated. Typically, these digital backs attach to a studio camera much like a Polaroid back. The price of these high-end devices remains in the exclusive domain of professional photographers., and as you might suspect, the quality is quite good.
Fortunately, the cost of these digital marvels is going down. I predict devices such as these will eventually outsell traditional (film) cameras - and for good reason. They are convenient, fast, quiet to operate, environmentally friendly, and fun to use.
Hand scanners are useful for their portability and low price (often one-third to a quarter of the cost of a flatbed scanner). Hand scanners generally plug into a computer's printing port, as opposed to a SCSI port, allowing them to be easily shared from workstation to workstation. Many people find them ideal for use with a notebook or laptop. Unfortunately, hand scanners are less accurate than flatbeds because they have weaker light sources and often produce uneven scans - courtesy of the unsteadiness of your hand or the surface you're standing on. Many hand scanners now offer an alignment template to help guide you when scanning. At least one manufacturer ships a motorized "self-propelled" unit to help stabilize its scanner.
High-end hand scanners offer 400 spi resolution and 24-bit color - allowing you to achieve reasonably high-quality results. But their 4" to 5" wide scan head forces you to make multiple passes to scan even average-sized documents. You'll need to use the supplied stitching software to merge these partial scans back together again - a time consuming task. Nonetheless, hand scanners are very popular and are capable of high-quality, quick and easy, low-cost scans.Drum Scanners
Professional color trade shops wouldn't think of using anything less than a drum scanner for producing color separations for high-end printing. Instead of using CCD technology, drum scanners use PMT (Photo Multiplier Tube) technology for greater dynamic range and color accuracy. They also cost an arm and a leg, Nevertheless, drum scanners offer features not available to desktop scanners such as direct conversion to CMYK, auto sharpening, batch scanning, greater dynamic range, and huge image scanning areas. Ironically, most drum scanners don"t support preview mode - drum scanner operators are more interested in numbers than what the see with their eyes. Yet what truly sets drum scanners apart is their increased productivity. Since the process of scanning to CMYK is automated, drum scanners can produce more scans per hour than a desktop unit.
Digital Cameras
Digital cameras allow you to shoot three-dimensional objects, much like a regular camera, except you don"t have to wait for film developing and processing. Portable units are presently limited in storage and image size. Studio-only units offer larger image size and dynamic range, but require attachment to a host computer - hardly a portable solution. In the future, high-resolution, high-quality, portable units will surely come--they just aren't here now.
Previous incarnations of "digital" cameras weren't really digital - they digitally sampled the analog signal from a CCD as opposed to converting it to digital data. The resulting data was then stored on floppy disk. The floppy disk then had to be read by a special reader which converted the digital data back into an analog signal which then had to be re-digitized again using a video digitizer (see above) - what a mess!! As you might suspect, the quality wasn't much to write home about, either.Newer entry-level digital cameras, like Apple's QuickTake, are truly digital, i.e. they keep the signal (nearly) purely digital all the way from the CCD, to the floppy disk, to the computer. The secret is that they use massive compression of the digital data to get it all to fit on a floppy disk. Typically, these devices save from 7 to 32 "frames" of digital data at up to 640x480 resolution, and 24-bit depth. The quality is quite good - good enough for small (i.e. 2.5" x 3.5") reproductions in print, and certainly good enough for many multimedia purposes.More expensive mid-level digital cameras such as Kodak's DCS 200 use higher resolution CCD arrays (1024x1600) and high-capacity micro hard disks to store all that data. The DCS 200 also uses compression to squeeze all that data onto the hard disk. Optional features include digital modems for sending the images back to a "home" office.High-end digital backs, such as the Leaf Digital Back (for Hasselblad and Mamiya), use even higher resolution CCDs (2000x2000 or more), higher bit depth (12-bits/sample), higher dynamic range, no compression, and high-speed cables to connect the device directly to a computer, where the image is stored and manipulated. Typically, these digital backs attach to a studio camera much like a Polaroid back. The price of these high-end devices remains in the exclusive domain of professional photographers., and as you might suspect, the quality is quite good.Fortunately, the cost of these digital marvels is going down. I predict devices such as these will eventually outsell traditional (film) cameras - and for good reason. They are convenient, fast, quiet to operate, environmentally friendly, and fun to use.
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