Scanned image quality ranges from the crude and clumsy results produced by inexpensive hand scanners to the expensive but brilliant results that can come from high-end drum scanners. Flatbed scanners have always provided a middle ground, affordable but not up to the professional standards (or price) of drum scanners.
Using improved CCD (charge-coupled device) technology, the three new color flatbed scanners in this review create a balance of quality and price (under $3500) that can answer the needs of graphics professionals. With 600-dot-per-inch resolution and an increased tonal range that begs comparison with expensive drum scanners, the Agfa Arcus Plus, the Microtek ScanMaker III, and the Umax PowerLook PS2400x promise to handle all the color scanning needs of many users, and most of the scanning needs of many more.
All three ship with full versions of Photoshop. With each, a plug-in for Adobe Photoshop lets you scan directly into Photoshop in both Macintosh and Windows environments; if you have a preference for another program, other software vendors have offerings that can use the same filters. Scanning on the PC platform also relies on the TWAIN interface.
Each of the scanners is offered with a transparency adapter, but the low frequency with which large-format transparencies are submitted makes this option of limited value for most users. Most transparencies that are provided are 35mm, and the hardware resolution of these units is not sufficient for typical image needs from an original that small. It would be better to use the price of the transparency adapter to start a savings account for acquiring a slide scanner such as the Nikon Coolscan or the Microtek 35T.
The ScanMaker has a scan area (8.3 by 14 inches) that's 2 1/4 inches longer than the others', but the three scanners are very similar. All three consider the front of the unit to be where the top of the image is, and all have at least some curve in the case or lid to make lifting the lid easy. Agfa puts the power switch on the side of the unit, Microtek puts it at the very back, and Umax not only puts the switch at the front but turns the lamp off after extended periods without use. For all three, it's reasonably easy to set the SCSI device ID. In short, until you lay an original on the glass, there just isn't much difference among these units.
High Expectations
I evaluated the three scanners based on criteria developed from my experience in a range of digital publishing activities and from experiences shared by others doing similar work. Speed is always important in publishing, as is flexibility. A wide variety of originals comes over the transom, ranging from offset-printed (and therefore screened) publicity photos, to ``drug-store'' prints, to professional 8- by 10-inch prints, to typed text intended for OCR (optical character recognition). A scanner must have adequate resolution and tonal range to digitize all types of images accurately.
Each of these scanners uses a 600-element-per-inch CCD assembly to give true 600-sample-per-inch capability along the width of the scan, and each has a stepper motor capable of 1200 samples per inch along the length of the scan. Each also offers the capability to save higher-resolution files (up to 2400 dpi) through software interpolation, which creates intermediate dots through an averaging process.
High resolution is important mostly if you're processing the image through a high-end color system that carries continuous tone data from the scanner through final film output. Such systems are sometimes able to modify the shape of the halftone dot to preserve clarity within the final film. This means that very high resolution scans can improve the sharpness and clarity of relatively coarse halftones.
If you're using a PostScript imagesetter or a laser printer, high resolution isn't so important. Every dot of a given screen value (line screen value and density) has the same shape. As long as the image is scanned at a sampling rate sufficient to ensure that there are no interference artifacts between the scan and the halftone dot structure, no additional benefit results from higher resolution.
High resolution can help in reproducing line art. I have scanned prescreened artwork as line art and reproduced it reasonably (the result was not as sharp as you'd have if you obtained the original FreeHand file, but it was useful in a newspaper setting). Using the highest interpolated value, scanning in gray scale, sharpening the image, and then converting to a black-and-white image at final printer resolution is as close to a good photographic process as you can get with PostScript output devices.
Tonal Range
It is important that the scanning resolution be high enough to get the best image the output system is capable of, but no higher. For most images, the scanner's dynamic range--its ability to register a wide range of tonal values--contributes more to the final image quality than high resolution does. The reviewed scanners have rated dynamic ranges of 2.8 for the Arcus Plus and 3.0 for the ScanMaker and the PowerLook. (For transparencies, add 0.1.) For comparison, dynamic-range values for less expensive scanners are typically below 2.5, and those for drum scanners range from 3.0 to 4.0, depending on price.
In any presentation medium, there is a range of possible tone values that can be reproduced, from something near white to something near black. Because there are abrupt shifts between the smallest dot that can be printed and solid white or black, it is normal to narrow the range on the printed page to that which can be consistently reproduced.
Even if the presentation medium cannot reproduce a particular color, the eye can be tricked into seeing more colors as long as the input colors are carefully mapped to the output colors. If the brightest highlight in the original becomes the brightest tone in the printed output, and the brightest green in the original becomes the brightest green in the final product, the eye maps these reproduced colors to something close to their original values if--and it's a critical if--the relationships between the printed tones are smooth and realistic.
For this to work, the scanner must be able to detect a large range of input colors, and the scanner driver software must handle the color mapping smoothly. A scanner with insufficient dynamic range will fill in the shadow areas or lose all detail in the highlights in an attempt to fill the color gamut of the final presentation medium. These scanners all have sufficient range to completely fill the offset-printing gamut.
SCSI Setup
My network consists of two 486 PCs and a Quadra 700 flanking a LANtastic bridge/server. Each scanner installed within 5 minutes on the Quadra, but they provided experiences ranging from annoying to disastrous on the PCs. One PC that had two ASPI-compliant (advanced SCSI programming interface) SCSI host adapters refused to scan into Photoshop with any of the scanners, although a Corel LS2000 card allowed Corel's scanning application to use the PowerLook.
Each vendor's installation indicated that its scanner worked with the Adaptec 1542 controller, and Agfa included that card with the review unit. (Agfa does not bundle the Adaptec controller, but most of its PC customers use this controller with Adaptec's EZ-SCSI software to drive the Arcus Plus.) However, I couldn't get the Adaptec card to work in my system because of a hardware malfunction, and I wasn't able to replace the card in time for this review.
I tested both the PowerLook and the ScanMaker on the PCs using the scanners' proprietary SCSI cards. It seems odd to have three SCSI host adapters in one computer (one each for the hard drive, the CD-ROM drive, and the scanner). However, if your system isn't full of cards, it may be simpler just to install a controller dedicated to the scanner than to attempt getting one SCSI host adapter to work with several SCSI devices.
Test Results
Experienced users develop techniques to enhance whatever image their scanner is capable of. However, any image will lose information during such modifications, and the better the original scan, the better the final product. For inexperienced users, starting with good scans will make your earliest jobs look better and your learning quicker and less frustrating.
Each of the reviewed scanners includes substantial automatic calibration and scanning intelligence. The Arcus Plus and the PowerLook check their light sources and CCDs before each scan; the ScanMaker uses calibration information based on an Agfa reference target. I scanned the test image using each vendor's automatic calibration and ranging features, with no color modification or image sharpening.
I chose the chipmunk photo, an 8- by 10-inch print provided by Clare Hollingsworth, as a test image for several reasons (see the scans). The photo provides plenty of detail, as well as subtle color data in the out-of-focus background. I assumed that the manufacturers had done plenty of scanning of standardized calibration targets and didn't expect that one more such test would be meaningful.
The general rule of thumb for scanning is to sample at twice the expected halftone value, but my experience is that anything over the square root of 2 to 1 wastes scanning and manipulation time, as well as storage space. For the sake of testing, however, I used a 2-to-1 ratio to scan the image. Based on the 133-line screen that most heat-set web offset magazines use, I attempted to scan the test images at 266 dpi.
A drum scanner, the Crosfield Scantex at a Seattle-area color service, provided a comparison scan (the first scan in the sequence on page 138). I instructed the service bureau to use the basic ``closest match'' settings of the scanner and to scan and save the file at an appropriate resolution for PostScript output. The color service scanned the original at 120 samples per centimeter (304.8 dpi), creating a 31.5-MB image file.
The basic scan is pleasing, with a very slight green cast that you could run unmodified or compensate for readily in Photoshop. The master channel histograms (see the screens above the scans) show that each scan has enough information across the tonal range to provide a good image. The smooth and continuous curve in the drum-scanner image's histogram indicates that you could make reasonable adjustments without creating problems. The ScanMaker's scan came closest to the results from the service bureau, providing a smooth distribution of light and dark pixels without gaps and spikes.
Such discontinuities in the Arcus Plus and PowerLook images indicate that, once the scans are balanced, there will be gaps that can lead to some posterization and other artifacts during subsequent editing of the file. Shifting the midpoint of the Arcus Plus scan in Photoshop to lighten the image created a histogram almost as spiky in the dark half of the range as the PowerLook scan, with lower saturation. Increasing the saturation would increase the discontinuities in the histogram, which eventually become visible in the final printed image, particularly in areas of gradual and subtle changes in tone.
The ScanMaker accomplishes its smooth histogram by scanning at 12 bits per color and sending all that information to the computer. Tonal adjustments are made to this data, and only then is the image sampled down to 8 bits per color. The other scanners start with 10 bits and work down from there. When a standard format is established to use 48 bits of color information instead of 24 (32 bits after conversion to CMYK), the ScanMaker will be able to take advantage of the additional information immediately.
Because PostScript output devices can image a theoretical maximum of only 256 grays regardless of the incoming information, there would be little change in the final results of scans handled automatically. However, scans that require significant color correction could be processed at the higher bit depth and sampled down to 8 bits after all corrections have been made, resulting in a final histogram that looks like the drum-scanner or ScanMaker curve shown. Because Photoshop is currently limited to 8 bits, any modification to the ScanMaker scan would result in a spiky histogram in the final file.
While the differences in scanning out-put between the three review scanners are important, just as important are differences in the features and ease of use provided by the bundled scanning software, particularly if you deal with less-than-perfect images.
Arcus Plus FotoLook
Although it certainly has every useful option, the Agfa FotoLook software that comes with the Arcus Plus is confusing. When you're first starting the plug-in, for example, it is obvious how to choose the mode and order a preview. As with all scanning software, you then adjust the area that you will actually scan. Unlike with any other software I've used, however, the frame of this area must be dragged back out to full screen manually or the next preview will be only the size of that previous scan. Also, FotoLook's ability to select the black point and white point in the image--similar to what Photoshop lets you do in the Levels dialog box--is a nice feature, but it takes two prescans to get there. The software urgently needs usability testing to eliminate clumsy and counterintuitive elements such as these.
The software manual doesn't help, either. The first half has instructions that apply to all Agfa scanners, replete with notations that a given feature doesn't apply to one or more scanners in the line. The same information covers both Windows and Mac software, although all the screen captures are from the Mac version. The second half of the manual is devoted to installing the scanner in every European language. I'm sure I saw an index, but it's hidden in the middle of the volume. The manual is in serious need of a good set of tabs to indicate the sections and locate the index. Better yet, Agfa should edit this manual down to a single model, platform, and language.
I scanned the test image at 266 samples per inch, 50 percent scaling, with all other defaults set. This should have resulted in a 4- by 5-inch image of about 4 MB in size, but Photoshop reported that the final image was 8 by 10 inches at 150 dpi, for a file size of 5 MB. This additional file size is not enough to explain the slow scanning time of 5 minutes, 8 seconds.
ScanMaker III Software
The Microtek software includes DCR (Dynamic Color Rendition), the company's calibration and color-matching software that ensures the color integrity of the raw scanned image, and ColorSync, an Apple System Extension that aims to reduce color differences between the scanner, monitor, and color printers. Microtek includes device profiles for Apple monitors and Microtek scanners; profiles for most monitors and color printers are available from their manufacturers.
The DCR calibration utility, which Microtek recommends you use as a monthly task, takes only a couple of minutes and results in the color most closely matching the original image. The closest setting available to the 266 called for was 270, and I scanned the test image at that value. The scan completed and displayed in Photoshop in 2 minutes, 22 seconds.
Software installation on the Mac consists of dragging one folder of device characteristics into the Preferences folder, one Control Panel to the System folder, and two plug-ins to the appropriate folder for Photoshop. In addition to running a standard installer program, Windows users must allow for a 16-KB address block in upper memory between 640 KB and 1 MB for the interface card and be prepared to edit WIN.INI and any memory manager CONFIG.SYS entries to account for that address block.
Documentation for the Windows product is adequate, but you won't need it after installation. The documentation for the Mac product is best left in the box, as it doesn't properly describe this scanner and software combination. In both cases, the documentation is in too many pieces and lacks clear organization.
The software lacks one important feature and includes one aggravation. No facility is included for descreening. The software included with the other two scanners does a better (and certainly faster) job of this than can be done in Photoshop with the Despeckle and Sharpen filters.
The aggravation is that only inches and centimeters are available for scan size--two choices I rarely use. For page layout, I need picas. The rest of the scanning that I do (a growing part in this age of multimedia) is for on-screen display, where the desired size is known in pixels.
The preview window is also the smallest of those of the three software bundles and is too small for accurate cropping. Thanks to this and the lack of appropriate units of measure, I found myself scanning a generous area of most photos at a slightly higher resolution than I was likely to need, and then cropping and resampling in Photoshop.
PowerLook MagicScan
The Umax MagicScan software is the best of the bunch. Installation also consists of an installer for Windows and for the Mac--three files (four if you install the Help file) that you drag to the predictable locations on the desktop. The Umax interface card for the PC requires only an I/O address; if you know the address of your network card or other I/O addressed peripherals, the installation is trivial.
The MagicScan software offers a wide range of useful controls for dealing with less-than-ideal originals. If the print of the chipmunk had started with an off-color tone, the overall color cast could have been changed in the preview so that color information wouldn't be lost in Photoshop during corrections. There are three levels of unsharp masking available, although this operation is normally the last stage and should not be applied if other corrections are going to be made in Photoshop.
MagicScan allows easy and intuitive inversion of negative images, as well as flipping of images from transparent originals that were placed upside down on the scanner. A simplified histogram and tone curve are available for correction. The only feature I missed was scanning in picas, although pixels are directly supported.
The MagicScan manual, a slender paperback, is a model of clear and complete explanations and careful organization, and yet it's hardly needed because the basic functions of the plug-in are so obvious. I didn't even open it until the review was almost finished.
Like the Agfa software, MagicScan allowed me to enter the exact resolution I wished to scan in; unlike the Agfa software, it then delivered it. The scan, which could benefit from a slight increase in saturation, was quite pleasant, with the automatic balance selected and all other settings left at their defaults. The image was ready to edit in Photoshop in the remarkable time of 50 seconds. This is the only scanner that would not be objectionably slow if you also handled moderate amounts of OCR.
Clear Choices
Can these scanners eliminate the need for a service bureau? In many cases, the answer is clearly yes.
A scan from a service bureau typically costs $75 and takes two days, so just the speed and cost advantages of desktop scanning are enough to overcome a significant quality difference. Moreover, the benefits of drum-scanner quality will be lost if the film is destined for output on PostScript imagesetters. And in many cases, the original image is not good enough to reveal the quality difference of a drum scanner anyway.
The advertised features of the three scanners are similar, and the final quality of the scans is, in all cases, very high. With any of the three you can obtain image quality similar to that in this magazine or the national newsweeklies. The differences between them lie in the amount of work needed to get pleasing color.
Slow scanning speed, poor color accuracy, and a clumsy interface combine to keep the Agfa Arcus Plus off the recommended list. Agfa will be replacing the Arcus Plus with the Arcus II soon after you read this. The new scanner promises to be better all around, providing increased scanning speed and better image quality, with a 3.0 dynamic range and 12-bit sampling per color. The scanning area will increase to 8 by 14 inches. The price, somewhere under $4000, will include a built-in transparency adapter. Until that new scanner proves itself, however, the clear choice is between the Microtek ScanMaker and the Umax PowerLook.
The ScanMaker offers the best color rendition, and the dense histogram it produced means that more image modifications can be made without losing important information. The increased bit depth will be valuable when and if Photoshop supports a 12-bit-per-pixel file format. Shops doing predominantly color reproduction with good originals should put the ScanMaker III at the top of their list.
The PowerLook has the convenience of quick scanning and software with suitable units of measure and a good descreening algorithm. These features make the PowerLook the more productive choice for shops that handle a wide range of scanning tasks.