Nanao's and Nokia's best monitors set a new benchmark for 21-inch CRTs--flicker-free at 1600 by 1200 pixels
Steve Apiki
For the manufacturers of the next generation of high-resolution displays, high-quality 1600- by 1200-pixel resolution on a 21-inch screen presents formidable technical challenges. The Nanao FlexScan F780iW ($3999) and the Nokia Multigraph 445X ($3225) are the first mainstream PC and Macintosh monitors capable of flicker-free 80-Hz refresh at 1600 by 1200 pixels. But while both are excellent displays, they arrive at the next high-resolution frontier by two very different paths, and not without trade-offs.
The technical challenge in building a high-quality, high-resolution display is simply one of numbers. Displaying 1600- by 1200-pixel resolution on a 21-inch screen requires a dot pitch of 0.26 mm or finer, but
putting more phosphor dots on a big screen increases the chance of manufacturing defects. The combination of large tube and small spot size also calls for more precise electronics because the alignment of the scanning electron beams is more critical.
Because so much of a large screen image falls in your flicker-sensitive peripheral vision, the electronics in a 21-inch monitor are further pushed by the need for a high vertical refresh rate. A 76-Hz refresh rate is flicker-free for many people, but 80 Hz is better. Displaying 1600 pixels by 1200 pixels by 80 screens per second requires a very large bandwidth. (In fact, very few graphics cards can drive these monitors at the 200-MHz bandwidth required for this screen mode.)
To meet these demands, Nanao has chosen a traditional approach that provides uncompromised image quality at high resolution but limits the FlexScan's capabilities on the low end. Nokia's design is more radical, relying on digital tuning of display parameters to overcome display
defects and provide more flexible configuration. I worked with both of these high-end monitors and ran them through quantitative tests in the BYTE Lab to measure performance. By both quantitative and qualitative measures, the FlexScan is the better monitor, despite Nokia's more revolutionary architecture.
Nanao FlexScan F780iW
As the new top of the FlexScan line, the F780iW has a great pedigree. Like the other models in that very successful line of monitors, Nanao's latest FlexScan is well designed and delivers outstanding display performance: sharp, bright, uniform, and flicker-free at 1600- by 1200-pixel resolution.
The cost of great high-resolution performance, unfortunately, is lack of support for standard VGA modes. This is the F780iW's weak spot. Monitors can perform optimally over only a limited range of frequencies, even within their specified bandwidth. Rather than sacrifice optimal performance at high resolution, Nanao decided to shift the horizontal frequency range upward, putting
the lowest supported horizontal scan frequency at 45 kHz--above the standard VGA scan rate of 31.5 kHz. That means that the F780iW is unable to support the boot video mode of most PCs, so it's relegated to use as a second monitor.
Nanao's fix is to offer the FlexScan bundled with a modified 4-MB Matrox MGA Ultima Plus graphics board ($4999 for monitor and board). The MGA Ultima's built-in VGA can drive the F780iW at boot-up; equally important, the modified MGA Ultima includes a 200-MHz color DAC (D/A converter) chip and is set to support refresh rates of up to 76 Hz at 1600 by 1200 pixels.
For almost any application except CAD, a second monitor for booting is an unreasonable requirement. I ran the FlexScan with an MGA Ultima, so using it as a primary monitor for Windows applications was practical, and the board and monitor combination worked fine.
Once past the boot, the FlexScan's display was great. Running AutoCAD, the monitor's ability to run the visible image to the edge of the displ
ay bezel without black borders (a capability that Nokia's monitor shares) was wonderful. It put AutoCAD's top and right menu borders square up against the edge of the screen.
Windows is often a stringent test of monitor capability, as the large, bright display background easily shows any nonuniform brightness characteristics. The FlexScan showed a bright Windows display with high contrast, although there was a small, slightly pink diagonal region. When it was running in one area of the BYTE Lab, near a large linear power supply, the FlexScan also showed some flicker interference that did not affect the Multigraph. As an FCC Class A device, the FlexScan may also generate more EMI/RFI in addition to being more sensitive to interference.
The FlexScan's display was sharp at all corners. Nanao uses two optimizations, Dynamic Focus and Dynamic Beam Spot Control, which help to improve sharpness away from the center of the screen. These technologies compensate for changes in focal length across a scan a
nd keep the electron-beam spot circular on all areas of the tube.
Nokia Multigraph 445X
Nokia's Multigraph tackles the image-consistency problem from a new angle. Instead of having a single set of analog beam adjustments that optimize display quality at the center of the screen, the Multigraph provides digital control over 16 adjustment points, which cover the center, the corners, and selected points in between. This is new technology--as of this writing, only Nokia offers a monitor with this capability. Philips, which has announced a similar system, was not able to deliver a production unit in time for this review.
Parameter adjustments are made on the fly, but the targets for each adjustment point are preset, since there is no feedback mechanism to enable the monitor to measure its own performance. The targets, stored in EEPROM, are set at the factory to compensate for individual variances in each tube and to provide a uniform image. A service technician can also readjust a monitor if it ch
anges over time.
Despite these compensations, the Multigraph simply did not perform as well as the FlexScan. In fact, Nokia's own ratings for misconvergence (0.3 mm at center) and luminance uniformity over the screen (70 percent) are only average among 21-inch monitors.
The Multigraph is also unusual for the level of control the user has over monitor parameters. In addition to the image size, location, and trapezoid and pincushion settings typically found on high-end monitors, you can also set convergence, color temperature, white uniformity, and other parameters through a menu that pops up on-screen when you hit a button on the front panel.
The on-screen menu has a few glitches. It sometimes has trouble displaying when you switch the frequency of the main display, and although it's designed to appear when the monitor loses sync, it sometimes continues to flicker on and off well after sync is lost. However, compared to the FlexScan with its limited palette of front-panel adjustments, the
Multigraph is considerably easier to tweak to your liking.
Although Nokia's monitor held a rock-steady 1600- by 1200-pixel image at 80 Hz, the display had some minor problems. Despite making numerous adjustments to contrast, brightness, and focus, I was not able to get quite as clear or bright a display on the Multigraph as I could get on the FlexScan. Convergence also remained noticeably off at the sides of the display, again despite adjusting it through the menu. Finally, running Windows with a bright white background showed a large yellowish area just off the center of the screen, as well as a few smaller spots in other areas.
The Best Parts
These are high-end monitors by any measure, including price: The FlexScan sells for $3999, and the Multigraph for $3225. At these stellar levels, you expect a top-quality monitor, so both Nanao and Nokia have included high-end design elements beyond those directly related to bandwidth and image uniformity.
Both monitors have a conductive antire
flection panel that provides the best antiglare/antireflection performance available on PC displays. Unlike a diffusion coating, which diffuses reflected light, the antireflection panel absorbs most incident light without diffusing transmitted light from the image. Both the FlexScan and the Multigraph had very low reflections and were easy to use even in an office lit by fluorescent tubes.
Besides cutting reflections, the antireflection panel includes a conductive element that cuts static buildup and electromagnetic radiation through the screen. This second characteristic gives both CRTs low-enough emissions to conform to Sweden's TCO standard, which is more rigorous than MPR-II.
Behind the glass, both the FlexScan and the Multigraph use Invar shadow masks (which are less sensitive to thermal changes) and medium-short-persistence phosphors (which have a wide chromaticity range). These elements are common in most high-end CRTs.
These two monitors also include roughly comparable power cons
ervation features for reduced power consumption in standby modes. The FlexScan supports the VESA DPMS (Display Power Management Signaling) specification, while the Multigraph complies with the Swedish NuTek standard. However, both of the monitors implement their power-down features in such a way that they will work even if you don't have a "green" PC or workstation; all they require is a blank screen saver.
Spot Comparisons
Besides the qualitative comparisons gleaned from Windows and AutoCAD, I made quantitative measurements of display quality using a Microvision SuperSpot monitor-test unit (see the figure "SuperSpot Test"). The SuperSpot measures line size and a host of other parameters for each screen using an optical sensor and computer-controlled display patterns. I made these measurements at 1024- by 768-pixel resolution with a 60-Hz refresh rate, so keep in mind that these tests don't push the monitors to their limits.
I evaluated the FlexScan F780iW with the special Matrox Ultima card
Nanao recommends; Nokia supplied an Infotronic IGP64 PCI1600 card with the Multigraph 445X. Both cards use the 200-MHz color DAC necessary to drive 1600- by 1200-pixel resolution at an 80-Hz refresh rate, although the Matrox card goes to only 76 Hz at that resolution. Both monitors work with either card.
Many of the SuperSpot's test results, including those for line width, were very close for these two monitors, so only the few results that show differentiation are graphed in the figure. The FlexScan was uniformly better for the following tests: difference between horizontal and vertical line sizes, convergence, and time variations for luminance and beam position. But for each of these tests, the results for both the Multigraph and the FlexScan are very good relative to results for lower-resolution devices.
Taking both the SuperSpot measurements and the qualitative results into consideration, the Nanao FlexScan F780iW is the clear winner. While neither monitor is inexpensive, the FlexScan costs
over $750 more than the Multigraph 445X. But in the display-sensitive CAD and imaging arenas where these monitors will first make their mark, the price difference will not be much of an issue.
The Facts
Nanao FlexScan F780iW..................$3999
Bundled with Matrox MGA Ultima
Plus 200-MHz controller................$4999
Nanao USA Corp.
23535 Telo Ave.
Torrance, CA 90505
(800) 800-5202
(310) 325-5202
fax: (310) 530-1679
Nokia Multigraph 445X..................$3225
Nokia Display Products, Inc.
3000 Bridgeway Blvd.
Sausalito, CA 94965
(800) 296-6542
(415) 331-0322
fax: (415) 331-0424
Monitor Capabilities Compared
Top-of-the-line monitors use the best consumer technology to present accurate, clear images on large screens and at high resolution. Among the optimizations both share are 200-MHz bandwidth, antireflection screen panels, a full-screen viewing range, Invar shadow masks, and phosphors with a wide chromaticity range.
NANAO FLEXSCAN F780IW
Size (in.) 21
Dot pitch (mm) 0.26
Maximum resolution (pixels) 1600 x 1200
Refresh rate at highest resolution (Hz) 80
Horizontal scanning frequency (kHz) 45-100
Vertical scanning frequency (Hz) 55-120
Visible screen area (mm) 403 x 298
Video bandwidth (MHz) 200
Screen treatment Conductive antireflection panel
Controls
Control type Front panel
Presets (factory/user) 9/19
Shadow mask type Invar
Phosphor type Medium-short
Power consumption (W)
Active 160
Standby 16
Power-down 11.2
Regulatory approvals
Emissions MPR-II, TCO 92
Flicker ISO 9241-3
EMI/R
FI FCC Class A
Dimensions (H x W x D; in.) 19.1 x 19.7 x 21.1
Weight (lb.) 83
Warranty 3 years
NOKIA MULTIGRAPH 445X
Size (in.) 21
Dot pitch (mm) 0.25
Maximum resolution (pixels) 1600 x 1200
Refresh rate at highest resolution (Hz) 80
Horizontal scanning frequency (kHz) 30-102
Vertical scanning frequency (Hz) 50-120
Visible screen area (mm) 400 x 300
Video bandwidth (MHz) 200
Screen treatment Conductive antireflection panel
Controls
Control type On-screen menu
Presets (factory/user) 14/14
Shadow mask type Invar
Phosphor type Medium-short
Power consumption (W)
Active 160
Standby
15
Power-down 8
Regulatory approvals
Emissions MPR-II, TCO 92
Flicker ISO 9241-3
EMI/RFI FCC Class B
Dimensions (H x W x D; in.) 20.4 x 20.2 x 19.7
Weight (lb.) 71
Warranty 3 years
Illustration: Comparing screens between the FlexScan F780iW (left) and the Multigraph 445X shows that both displays provide clean, sharp lines and good convergence. However, despite tuning monitor parameters for this shot, the FlexScan provided somewhat better contrast and less luminance variation over the white areas.
Figure: SuperSpot Test
BYTE's display-quality measurements show a slight but consistent advantage for Nanao's FlexScan over Nokia's Multigraph 445X. Note that all measurements were made at 1024- by 768-pixel resolution at 60 Hz, so these tests do
not fully stress either monitor. The top-left graph shows the difference in size between horizontal and vertical lines, a measure of the sharpness of the electron beam. The top-center graph shows convergence error at the center of the screen; both monitors have excellent convergence (BYTE tuned the Multigraph for best convergence). The remaining graphs chart image variations over time, which reflects the steadiness of the display. Although the FlexScan performs somewhat better than the Multigraph, both of these monitors show almost negligible luminance and position variation.
Photograph: Nanao's FlexScan F780iW (left) and Nokia's Multigraph 445X define the leading edge in monitor technology, with 1600- by 1200-pixel resolution at an 80-Hz refresh rate. The FlexScan sacrifices low-end graphics support for excellent performance at high resolution, while the Multigraph 445X relies on digital fine-tuning to enhance display quality. Both monitors provide a wide variety of configuration options--
the FlexScan through the front panel, and the Multigraph through a configuration menu.
Steve Apiki is a BYTE contributing editor and former director of the BYTE Lab. He is senior developer at Appropriate Solutions, Inc., a consulting firm based in Peterborough, New Hampshire. You can reach him on the Internet or BIX at apiki @bix.com.
Big-Screen Stars
