Specifications

SCANNERS
INTRODUCTION to SCANNERS
SCANNERS
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Drum Scanners
Professional print houses would-
n't think of using anything less
than a drum scanner for produc-
ing 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. It
works like this: the scanner
wraps the artwork around a cylin-
der and rotating at high speeds to
“split out” the individual parts of
the original image. Photo multiplier tubes pick up these pieces with
the help of a laser to create images with unbelievable accuracy.
Although very expensive, drum scanners offer features not usually
found on desktop scanners, such as 8000 to 11,000 dpi scanning
resolution, 48-bit color, direct conversion to CMYK, greater dynam-
ic range, and huge image scanning areas. Ironically, most drum
scanners don’t have a preview mode. That’s because a drum scan-
ner operator is more interested in numbers than what they see
with their eyes.
Handheld and Sheetfed Scanners
If you’re the office type, or are into small gadget-like scanners, then
you want a sheetfed or handheld scanner. These days, sheetfed
scanners generally come as part of multifunction print/scan/fax
home office units or as mini-scanners for memos and photocopies.
They incorporate weaker sensors to save space, and therefore offer
lower resolution and image quality. Some models can’t interpret
images, but can only scan text and translate it with OCR software.
Handheld scanners tend to mimic sheetfed scanners in ability, but
their drastically minimized hardware also suffers from the effects of
all the jitters and shakes of your hand. So, if you’re any kind of
photographer, these scanners are not for you.
Hand scanners are useful for their portability and low price. 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 note-
book 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 dpi 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 pop-
ular and are capable of high-quality, quick and easy, low-cost scans.
Film Scanners
If you are a professional photographer who doesn’t want to shoot
digitally, then a film scanner is for you. Film scanners are designed
specifically for negatives and slides, and they offer some of the
most advanced film-type detection, color reproduction accuracy,
and resolution technology available— however, they only let you
scan negatives and slides. For those who may need only an occa-
sional transparency scanned, a flatbed with transparency adapter
may be a better alternative. But for those who scan a lot of trans-
parencies, then a dedicated film scanner is the only game in town.
At the high-end of film scanners is the Multi-format transparency
scanner—allowing you to scan everything from 35mm slides all the
way up to 4x5-inch transparencies. These scanners are targeted to
professionals and do cost quite a bit more. In fact, these high-end
transparency scanners are moving-in drum scanners by offering
more features, better software, and faster scanning time.
The way to create large images to print is to use a film scanner to
scan the film instead of the prints. Often called slide scanners,
they scan both slides or negatives and most are for 35 mm film.
Scanning film is better than scanning prints, because scanning the
film is using the original image, while the print is a second
generation copy. Making a copy of a negative onto photo print
paper is like making a copy of a music CD onto a cassette tape. The
cassette tape isn’t bad, but it doesn’t compare to a CD.
Second, film has much more detail and contrast available. Film
s capable of over 3000 dpi, compared to only about 300 dpi for
color photo print paper. The 35mm film is a smaller original, so it
must be enlarged more, about 4 times more than a scanned 4x6˝
print, to get the same image size at the printer. However the film
and film scanner has well over 10 times more capability to do it.
Image size can be quite huge when scanning film, because you are
realistically able to scan at very high resolution. The huge size is
the entire point, for example to create enough pixels to print full
page size. You will want at least 128MB of memory, and more is bet-
ter. But a film scanner definitely does allow acquiring enough quali-
ty pixels to scale to print a large image.
For example, a full frame 35
mm color negative scanned at
2400 dpi will be about 3400 x
2200 pixels or 22 MB. Scanning
at 2400 dpi and printing at 300
dpi allows enlarging that print-
ed image 8 times more than the
original film size (2400/300 = 8).
Scaling by 8, so that the 1.4 x
0.9 inch film size (36 x 24 mm)
prints 8X larger gives 11.2 x 7.2
inches. It will look great in
regard to detail if printed at
200 to 300 dpi. Scanning film
originals can support this level
of detail. Scanning a 4 x 6 inch
photo will not.