Scanners yield quality images at any cost

Lab develops
scanner PowerIndex to compare various vendor models


After decades of niche marketing, this year desktop scanners are enjoying more
widespread success.


The forces that are pushing them out of the graphics department and onto more desktops
are cheaper photo-quality technology and the Web.


The GCN Lab tested seven desktop scanners from sub-$200 units up to high-end models
costing more than $2,500. Our goal was to sample the technology and the image quality now
available across the full price range.


All models were color scanners, but that was the only similarity.


We looked at 30- and 36-bit model scanners that connected via parallel port, Universal
Serial Bus or SCSI card, and units with optical resolutions from 300 by 600 dots per inch
to 800 by 1,600 dpi.


Bit depth refers to the number of bits assigned to describe the color of each pixel
captured from the page. Grayscale scanners capture 10 bits of information per pixel; color
scanners combine 10 bits of information per light channel—red, green and blue. That
means each pixel captured has three sets of color information adding up to a total of 30
bits.


Why do some scanners have 36 bits?


Extra bits ensure greater color accuracy and detail. A 30-bit scanner is capable of
capturing 1.87 million colors. With the six extra bits, a 36-bit scanner can differentiate
68.7 million colors.


The extra colors improve detail and realism. When a 36-bit scanner converts its capture
into a 24-bit file for your graphics application, it usually picks the best 24-bit range
of data. That means you get better images from high-saturation and low-contrast originals.


How the scanner connects to the PC can matter just as much as image quality. The three
common connection types affect your budget, your results and your patience.


Parallel port scanners are easy to hook up, especially if there is no printer occupying
the port. Most parallel scanners have a pass-through connector to use a printer at the
same time, but this can cause problems.


USB scanners, the new kids on the block, are the easiest to hook up as long as you have
a PC with a USB port or a USB input/output card.


SCSI scanners, the oldest type, still cost the most because they are fast and can
handle high-end images and multiple documents. To install one, you must have the
appropriate SCSI card in the PC.


Most SCSI cards that accompany scanners are SCSI-1 ISA cards. They often create
installation problems because they cannot take advantage of Plug and Play for Microsoft
Windows 9x. Because many computers soon will not have ISA slots, scanner manufacturers may
have to supply PCI SCSI cards and raise prices.


Interface speed isn’t as big a factor as you might think. USB’s maximum data
transfer rate is 1.5 megabytes/sec. A bidirectional parallel port delivers 600
kilobytes/sec to 1.5 megabytes/sec. SCSI-1 clocks in at 5 megabytes/sec.


You also need to know about TWAIN. It’s simply the protocol by which applications
communicate with a scanner. The acronym stands for tool kit without an interesting name.


Whether you work in Adobe Photoshop, Corel Photo-Paint or some other application, you
always use the same TWAIN driver interface to activate and manage scanning. That’s
why we closely examined TWAIN driver user interfaces on each scanner. The best drivers
were intuitive and didn’t sacrifice flexibility.


In the end, image quality often comes down to how many dots per inch the scanner
detects. Many vendors soup up their hardware and software to increase scanner resolution.
But the industry’s dirty little secret is that for most purposes, anything higher
than 300 by 600 dpi is overkill. Resolutions of 4,800, 6,400 or 9,600 dpi add nothing
unless you’re scanning line art, 35mm slides or negatives.


Resolution was not a problem in any scanner we tested. Correct color matching and
saturation values matter far more and vary more.


Equally important are a scanner’s light source, optics and charge-coupled device.
The CCD, also used in digital cameras, has a major effect on quality. The smaller the
range of light the CCD detects, the cheaper the unit and the poorer its image quality.
That’s why $200 scanners are not appropriate for high-end imaging.


For publication-quality scans, expect to pay $800 and up for a high-end scanner.


Epson America Inc.’s Expression 836XL turned in the best image quality in this
comparison. Its Expression 636 Pro 2 came in second. But the 636 Pro 2 is half the price
of the 836XL and comes standard with a transparency adapter, so the 636 is the better
deal.


It can connect via either a bidirectional parallel connection or a SCSI-1 card. We
recommend the latter if installing a SCSI card is easy.


The 636’s TWAIN driver showed a simple, user-friendly interface at first but
revealed more extensive controls as needed. The interface gives an image preview, manual
and automatic scan area selection and output optimization for different printers. Epson
listed only its own printers and generic choices such as “600-dpi laser
printer.”


The 636 line, available in Executive, Artist or Professional models, will meet high-end
needs for many users. The 636 Pro 2, which received one of our Reviewer’s Choice
designations for high-end scanners, is a good choice and a good deal for graphics
professionals.


The Epson Expression 836XL, the only large-format scanner we tested, is larger than the
636 Pro 2. It can scan even tabloid-sized pages up to 12.2 by 17.7 inches.


Priced at $2,528, the 836XL earned the highest imaging scores from our judges—more
than a point higher than the Epson 636, which in turn was a point higher than the
third-ranked scanner. The 836 also had the highest optical resolution of all units tested:
800 by 1,600 dpi. And it had the most complete calibration software of the bunch.


Unlike most of the other scanners, it did not work from a fixed focal point but rather
over a focal range adjustable through its TWAIN driver.


The 836’s TWAIN driver was the highest-rated in the review for its auto-image
selection, auto-focusing and great flexibility.


Overall, the Expression 836XL performed the best but cost the most. We recommend the
636 unless you must scan at 800 dpi or handle tabloid-sized documents.


Hewlett-Packard Co.’s gray ScanJet 6250Cse resembles a battleship with its
multitiered top—a change from the standard flatbed case.


The top tier is a 25-page document feeder. The paper tray loads like a standard laser
printer’s, and documents zip through quickly. Coupled with optical character
recognition software, the 6250Cse would make a fine tool for processing lots of documents.


One problem was that Hewlett-Packard tweaked the TWAIN driver for document scanning,
and image quality suffered under the default settings.


Clip art and rudimentary document-level images such as pie charts come through
unscathed, but photographs lose quality through oversharpening. Changing the sharpening
setting to None produced better image scans.


Until you figure out how to set defaults, the TWAIN driver interface may frustrate you.
For example, the sharpening setting enhances documents going to OCR by increasing detail.
But it exaggerates an image’s flaws and harms quality.


The 6250Cse comes with a 35-mm slide adapter, triangle-shaped to sit on top of the
scanning bed and bounce light behind the slide. It worked well for dark slides but washed
out lighter ones.


The 6250Cse’s big advantage is speed, whether for scanning one image or a large
text document.


In an office that handles slides, photographs and text documents, the 6250Cse would be
a good all-around performer.


The ScanJet 6250Cse received a Reviewer’s Choice designation not because it was
the best scanner in every category, but because it was the best overall. It meets many
different needs as a heavy-use personal or workgroup scanner.


HP’s ScanJet 4100C was one of two 300- by 600-dpi scanners in the comparison.
Judges scored it third in image quality behind the two much more expensive Epson scanners.
Although it did well at the quality tests, its scanning speed was the second slowest. Even
at 600 dpi in speed tests, the other 300- by 600-dpi scanner performed faster than the
ScanJet 4100C.


The 4100C would make a fine low-end scanner, but you will pay a slight price premium.


Memtek Products Inc.’s Memorex SCF 9612P scans in three dimensions. Sounds cool,
doesn’t it?


Although the Memorex could scan objects up to 21'2 inches off the scanning bed, the
feature seems only marginally useful.


The Memorex unit turned in the lowest image quality scores with poorly defined and dark
images. The automatic controls for color, brightness and contrast only made things
worse. Another mark against the Memorex is slowness. One 600-dpi scan of an 8- by
10-inch image took 13 minutes, 28 seconds.


Visioneer Inc.’s PaperPort 3100USB was a racehorse. It could blow through an 8- by
10-inch scan in the time other scanners took to preview an image. Images became 80M files
in a minute and a half. That’s not because the optical resolution is only 300 by 600
dpi—our other 300- by 600-dpi scanner, the HP 4100C, performed four times slower than
the 3100USB.


Image quality is about average. The 3100USB stays true to original colors. Zooming into
the scanned images, however, we saw its limits. The 3100USB is best suited for scanning
documents and low-resolution Web graphics. Among low-end scanners, you would be
hard-pressed to find anything better for $130.


The USB connection cable is a big plus and took no effort to plug into nearly any PC
with a USB port—another reason the 3100USB is an excellent choice for casual scanning
and inexperienced users.


The bundled PaperPort software also provides a headache-free document management and
scanning interface.


Visioneer’s PaperPort 6100B, the 3100USB’s big brother, shares many of its
advantages and flaws.


The 6100B came in second only to the 3100USB in our time runs. The difference in
scanning time may result from the way the 6100B connects by parallel port, which is slower
than the 3100’s USB connection.


The 6100B costs more than the 3100USB, but it did a better job with images that we
examined up close. The 6100B would make a good personal scanner for users who need
accurate images and OCR.


If Visioneer sold an automatic document feeder for this model, it might give the HP
6250Cse some competition. Also, the Visioneer 6100B is about $20 less than the
lower-resolution HP 4100C. It gets our Bang for the Buck designation.


It’s a chancy venture to search for a simple scanner that meets your needs and
turns out good images. Compare what’s on the market and weigh all the factors.
Don’t buy a scanner based on one specification such as number of color bits or
resolution.


Our roundup shows that some models succeed despite their faults. It also shows that big
numbers on the specs don’t necessarily yield the best images. Shop around and examine
scans from different models. In the end, your own eyes are the best judge.    


The GCN Lab solicited scanners from a number of vendors. I
requested both low- and high-end flatbed scanners with at least 30-bit color and 300- by
600-dot-per-inch resolution.


I also recommended that companies sending high-end scanners
include any optional equipment, such as document feeders or transparency media adapters.


The lab graded the scanners on price, ease of use, bundled
software, media flexibility and image quality. The judges were GCN reviewers and users
with extensive graphics experience. The lab rated how hard it was to set color and
calibration, scanning speed, and the TWAIN driver interface, and judged the total
out-of-box experience.


To compare the different models, the lab developed a scanner
PowerIndex. Out of a possible 100, 55 points went to scores for image quality, resolution
and color.


Ease of use, which included the TWAIN interface scores,
connectivity options and scanning speed, made up 32 points. Finally, capabilities for
handling multiple documents, transparent media and large documents added a possible 13
points.


All the high-end scanners scored higher on the PowerIndex, but,
as the charts show, their capabilities came at a price. Because the lab reviewed both
high- and low-end scanners, the PowerIndex shows the great disparity between the two.


But the scale still holds value for comparing low-end scanners
against one another. The Visioneer PaperPort 6100B, for example, scored quite a bit better
than its rivals in the low-end category.


For the image quality tests, I printed a number of images on a
Fuji Pictography 3000 photo printer and scanned them using each scanner’s TWAIN
driver under Adobe Photoshop 5.0.


If the scanner’s TWAIN driver had automatic settings, I took
advantage of that option. Otherwise, I simply scanned at the default settings. No
alterations were made to the images after they were saved as Photoshop .psd files.


I hooked up each scanner in turn to the same 400-MHz Pentium II
Xeon workstation. I timed how long it took for the scanner’s CCD element to capture a
single 8- by 10-inch color photo at 600 dpi. I stopped the clock as soon as the scanner
was finished but before the image came up on screen.


The formula for the scanner PowerIndex, as well as more samples
of the scanned images, appears in the Lab section on GCN’s Web site at http://www.gcn.com.  


—Jason Byrne

inside gcn

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