Go digital: Cadalyst Labs tests the latest wide-format scanners

CADalyst, April, 2004 by Ron LaFon

Many firms have a large number of original, hardcopy drawings and blueprints that have never been digital. Wide-format scanners provide the tools to convert these valuable drawings to digital formats, either as bit mapped images or through conversions to vector formats that you can edit in CAD applications or transmit to field offices. Scanners can become an invaluable part of a scan-to-print or copy system. They are also used in GIS offices to scan in existing maps and aerial photographs.

Many options are available, ranging from relatively compact monochrome devices to larger, more complex models that scan high-resolution 24-bit color images. This roundup looks at six wide-format scanners that incorporate very sophisticated technology. They really are technological and engineering marvels.

What We Requested

For this Cadalyst Labs roundup, we requested wide-format scanners that met two minimum requirements: the scanner had to support at least D-size drawings and had to have been released after July 2002. Six different scanners from five companies met those requirements.

How We Tested

The evaluation of these wide-format scanners is based on three factors: quality, speed, and ease of use. Each scanner warmed up for at least the manufacturer's recommended time--typically an hour--and then I calibrated using the included guides and software. Calibration typically took from 15 to 30 minutes, depending on the size and complexity of the scanner.

Once I calibrated a scanner, I fed the test image, a 27" X 21.75" 7.5-minute quadrangle USGS topographical map of the South Sister, Oregon, area into the scanner in portrait (horizontal) mode so that timings were based on the scanning of the shorter dimension. After the scanner pulled in and adjusted to the size of the original, I began the timings when the actual scan started and ended when the scan was complete.

Many manufacturers' rated speed is based on feeding an A-size sheet through the scanner, which makes our speed results different. The ips (inches per second) speed included in the online feature table is derived from the time and size of the original I used for testing.

I tested the optimal settings for each scanner to confirm that the lines were generally complete, that broken lines didn't merge into continuous lines and that colors rendered accurately without obscuring detail or, with monochrome scanners, to determine that the representation of a given color in gray didn't obscure important detail in the original. I set the mode and resolution the same for each scanner, 400dpi and 24-bit color or the equivalent in monochrome.

CHOOSING THE RIGHT SCANNER

Once you determine what sizes your paper documents are, think about how many scans you'll be making and how often. Some more-expensive models--such as the Oce TCS400--may pay for themselves because they're so easy to use, especially if you're making a large number of scans. All of the scanners here are capable. Some may be slower than others, but again, look at what you're using these machines for. In addition, the scanning software, which may be included or available as an option, is an important ingredient to your scanning solution. If you need to scan daily, but not continuously, perhaps one of the other models will work best for your office. They cost a bit less and take a bit longer to process.

Most scanners are basically a digital camera designed to capture flat art. Each has a CCD (charge-coupled device) that produces an image that is then converted to a usable digital format. The larger the scanner, generally the more cameras it includes. For example, the 54" Contex Magnum XL scanner from IDEAL.com has four cameras, one fixed and three that move. Western Graphtec's CS2000 doesn't use CCD cameras, but instead uses contact array sensor technology.

A wide-format scanner must feed the original evenly to prevent distortion in the scan and to protect the original. A jam that damages an irreplaceable original is not, as Martha Stewart would say, a "good thing." Typically, very thin originals, such as those on onion skin or similar papers, are the most prone to problems. You should feed such originals through the scanner in the plastic sleeve that comes with most scanners to prevent such problems.

Within reason, you can scan damaged originals and recover the drawing using the accompanying software. Once it acquires an image, the scanning software typically lets you adjust it, and then it converts the bit-mapped image into a vector file format.

Most scanners connect through FireWire, SCSI, or USB 2.x, as these connections can handle the large quantity of data moving from the scanner to your computer. The 24-bit color scans of our 27" X 21.75" test original averaged more than 300MB, and higher resolution scans of larger originals can easily top 1GB. Having adequate hard disk storage on your computer system is important, as is archiving these large files for long-term storage.

Scanning software applications vary in how capable they are and can easily exceed the cost of your CAD application or your workstation. Capabilities to check for include how much cleanup of an image is possible, whether it performs hole filling and despeckling, and what file formats are supported. The software usually includes a collection of presets that cover basic scan settings. You can usually modify them or create custom profiles if you have further needs.