Scanned on a Slide Scanner
Scanned on a Flatbed Scanner
Slide VS. Flatbed
As you can see from this comparison, dedicated slide scanners can discern differences in film types and are able to compensate for film differences to acheive best quality.
|The most popular type of desktop scanner is the ubiquitous flatbed scanner, so called because of its flat, glass platen (or bed) which serves as both the scanning area and surface for laying objects down to be scanned. Most flatbeds are used for scanning reflective art.
Entry-level flatbed scanners generally share the following specifications: 8-1/2" x 11" scanning area, 300 to 400 spi scanning ability (often interpolated to 800, 1200, or 1600 "spi"), 8-bits per color channel, and low cost. They often come bundled with powerful "value-added" software such as Adobe Photoshop. These machines frequently offer excellent price/performance ratio. Because there is fierce competition for this market, at the time of this writing, the magic price for entry-level scanners seems to be hovering around the $1000-$1200 mark.
Mid-level flatbed scanners differ from their entry-level cousins in three important ways: First they cost much more! Second, because they're targeted toward a more professional market, they rarely come bundled with "value-added" software such as Photoshop. Third, and most importantly, they have significantly better specifications. For example, a typical mid-level flatbed scans at 600x1200 spi and 10-bits per color, resulting in scans of significantly higher quality. Some mid-level scanners may also offer a larger scanning area.
High-end flatbed scanners are positioned as alternatives to drum scanners. They offer features that professionals demand:a noise-free design, large scanning area, high dynamic range, and high resolution. Expect to pay a premium price of for these scanners. Mid-level scanners are increasingly taking over this territory. Expect the lines to blur between mid-level and high-end flatbeds in the near future.
Multi-format transparency scanners allow you to scan everything from 35mm slides all the way up to 4x5-in. transparencies. These scanners are targeted to professionals only and thus cost quite a bit. In fact, these high-end transparency scanners are muscling-in on the once exclusive domain of drum scanners by offering more features, better software, and faster scanning time.
Slide scanners cost a lot more than the relatively inexpensive flatbed transparency option. For those who may need only an occasional transparency scanned, a flatbed with transparency adapter is the way to go. But if you scan a lot of transparencies, then the only equipment that offers the best quality scans are dedicated transparency scanners.
Today, most people use video digitizers for multimedia purposes, especially in the creation of QuickTime movies. But that shouldn't prevent you from occasionally using them to capture still images for print.
Video cameras utilize the same digital CCD arrays found in flatbed scanners. These CCD arrays produce an analog signal at (50 or 60 MHz) that either drives other analog devices such as VCRs and television sets, or is captured onto video tape. Video cameras technically aren't "scanners" in the truly digital sense of the word. But, the analog video signal can be (re-)digitized using specialized hardware and software. Video capture software is very similar to traditional scanning software, while the hardware is usually a board that fits inside your computer.
Although video cameras provide an inexpensive way to get images into your computer, you should be aware that the resolution will be low (only 640x480 pixels) and the dynamic range will be low (usually less than 2.5). The color accuracy will also be suspect. Nevertheless, video cameras are more than competent - in fact, I've been using them for image capture in my own work since 1987.
A category unto itself, Leaf's Lumina camera/scanner is a clever piece of equipment. Although it appears to be a digital camera, the Lumina is actually a scanner, albeit an unusual one. It uses standard Nikon bayonet lenses, which give it incredible flexibility. It scans at 2700 x 3400 and 36-bits deep for razor-sharp images and greater dynamic range. At a reasonable $6900, the Lumina may obviate the need to buy both a slide scanner and a flatbed scanner.
A pocket-sized device from Trio Information Systems allows you to convert any fax machine into a 1-bit scanner or printer using a standard fax-modem and proprietary Trio software.
Talk about specialized scanning! Pacific Crest offers a business card scanner that does just what its name implies - it is dedicated to those people who need to input and file tons of business cards! Who knows? It may be just for you.
Okay, okay, PhotoCD isn't really a type of scanner, but it is a useful way of getting images into your computer. All you need is a CD ROM drive hooked up to your computer and a roll of film you'd like to look at. Simply send the roll of film out to an authorized Kodak PhotoCD developer and for about $1.00 to $3.00 per image you get your film developed along with a CD-ROM containing your digitized images! Pretty neat, huh? Plus CD-ROMs are a great way to keep your image files organized. The quality of these scans is quite good and the proprietary PhotoCD format contains several sizes of each individual image for various uses. The largest size, 2048 x3072 samples, is just large enough for a full-bleed 8 1/2" x 11" image at 225 spi. (It also happens to be the same size as the propose HDTV specification - coincidence?). You can probably get a better scan by using a dedicated slide scanner (see below) and not compressing the resulting image. However, if you don't want to buy a slide scanner and learn how to use it, PhotoCD may be your best option.
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.
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 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.
Stand - Alone Oversize Digitizers
For very large originals up to 40" wide (such as architectural/engineering drawings) several manufacturers offer oversize, sheet-fed digitizers. These unusual devices are somewhat related to the automatic document feeders for flatbed scanners in that the original is pulled through the scanning mechanism. They differ in that the scanner head is stationary, in fact, they often bear a striking resemblance to CAD pen plotters. Because of the large image area involved, and subsequent large file size, roll-fed digitizers usually can only scan in line art and grayscale modes. Because of their uniqueness and specialization, these devices are also quite expensive.
|Design by:||Haywood & Sullivan|
|Copyright:||© 1996 Michael J. Sullivan|