Multiscan Computer Displays with FD Trinitron

GDM-F500 and GDM-F400

FD Trinitron Unprecedented image performance, featuring the finest aperture grille pitch available (0.22mm) and flattest Trinitron display ever, gives demanding CAD and graphic professionals the edge F Series
Tightest Aperture Grille Pitch Available 0.22mm aperture grille pitch across the entire screen Bright Picture, Sharp Images Sonys new HiDensity Electron Gun with Enhanced Elliptical Correction System technology Digital Multiscan Technology Supports the broadest range of PC and Mac display resolutions Stable, Consistent Color And Images Sonys GeoLockPlus circuitry provides improved color and brightness uniformity Easy To Navigate On-Screen Display DisplayMouse control allows for quick, smooth adjustments of the digital controls Instant Sizing And Centering Of Image Active Signal Correction (ASC) circuitry provides easy image adjustment at the touch of a single button Generalized Timing Formula (GTF) - Insures compatibility with varying video standards, reduces set-up time and maximizes the performance of the display system Reduced Depth Design Smart cable design allows for overall shorter depth of display on desktop Comprehensive Digital OSD Six languages with features such as image zoom, color and temperature adjustment, control lock, landing correction and information screen Dual Input Control 15 pin mini D-sub and 5 BNC connector options USB Compatibility Self-powered USB hub built into base with one upstream and four downstream ports
GDM-F500 Sony FD Trinitron Computer Display
CRT: 21" FD Trinitron (19.8" Viewable Image Size) Horizontal Scan Range: 30-121kHz Vertical Scan Range: 48-160Hz Maximum Resolution: 1800 x 1440 @ 80Hz Dimensions (WxHxD): 19.8" x 20.0" x 19.1" Weight: 70.5 lbs
GDM-F400 Sony FD Trinitron Computer Display
CRT: 19" FD Trinitron (18" Viewable Image Size) Horizontal Scan Range: 30-107kHz Vertical Scan Range: 48-120Hz Maximum Resolution: 1600 x 1200 @ 85Hz Dimensions (WxHxD): 17.5" x 18.7" x 17.9" Weight: 60.6 lbs

Specifications

CRT GDM-F500: 21" FD Trinitron GDM-F400: 19" FD Trintron Viewable Image Size GDM-F500: 19.8" GDM-F400: 18" Aperture Grille Pitch 0.22mm Screen Treatment Anti-Reflective Coating Electron Gun HiDensity Electron Gun with Enhanced Elliptical Correction System technology Horizontal Scan Range GDM-F500: 30-121kHz GDM-F400: 30-107kHz Vertical Scan Range GDM-F500: 48-160Hz GDM-F400: 48-120Hz Maximum Resolution GDM-F500: 1800 x 1440 @ 80Hz GDM-F400: 1600 x 1200 @ 85Hz Preset Resolutions (27 modes) 640 x 480 @ 60Hz VGA Graphics 640 x 480 @ 85Hz VESA 800 x 600 @ 85Hz VESA 832 x 624 @ 75Hz Macintosh 16" 1024 x 768 @ 75Hz Macintosh 19" 1024 x 768 @ 85Hz VESA 1152 x 864 @ 75Hz VESA 1152 x 870 @ 75Hz Macintosh 2-page 1280 x 1024 @ 75/85Hz VESA 1600 x 1200 @ 75/85Hz VESA 1800 x 1350 @ 85Hz Sony (GDM-F500 only) 1800 x 1440 @ 80Hz Sony (GDM-F500 only) and others Color Temperature Presets 5000 Kelvin 6500 Kelvin 9300 Kelvin 3 User-Adjustable Settings (Bias/Gain Control) Signal Inputs Analog RGB 0.7Vp-p, 75ohm Termination External Sync Signals Separate/Composite 1-5Vp-p, polarity-free TTL Sync on Green: 0.3Vp-p, negative Input Connectors 15 pin mini D-sub and 5 BNC connectors Power Requirements 100-240V AC; 50-60Hz Power Management International Energy Star, NUTEK and VESA DPMS Compliant GDM-F500 Operation: 140 watts (maximum) Suspend: 8 watts (maximum) Active Off: 1 watt (maximum) Power Off: <1 watt GDM-F400 Operation: 160 watts (maximum) Suspend: 10 watts (maximum) Active Off: 3 watts (maximum) Power Off: <1 watt Dimensions (WxHxD) GDM-F500: 19.8" x 20.0" x 19.1" GDM-F400: 17.5" x 18.7" x 17.9" Weight GDM-F500: 70.5 lbs GDM-F400: 60.6 lbs Operating Temperature 50F-104F (10C-40C) Operating Humidity 10%-80% (Non-Condensing) Regulation Compliance Safety: UL 1950 CSA 22.2 No. 950 EN60950 (TUV, GS mark) Emission/EMI: FCC Class B IC Class B MPR II TUV (full compliance) TCO 95 X-ray: DHHS DNHW PTB Ergonomics: ZH1/618, ISO9241-3, 8 Designed for: Microsoft Windows 2000 Windows 98 Macintosh Compatible Plug & Play: DDC-1, DDC-2B/A, DDC-CI DMI Compliant VESA: Generalized Timing Formula (GTF) Front Panel Digital Controls Power On/Off Active Signal Correction (ASC) Reset Brightness Contrast Input Switching Button On-Screen Display (OSD) Brightness/Contrast H/V Size H/V Centering Zoom Raster Rotation Pincushion Pin Balance Keystone Key Balance Color Temperature H/V Convergence: Top/Bottom Landing Correction (4 Corners) Moir Cancellation Manual Degauss Power Save Delay H/V OSD Position Control Lock Multi-Language Select (6 languages) Supplied Accessories Tilt Base/Wide Angle Swivel (90) Stand Video Signal Cable (15 pin mini D-sub) AC Power Cord Macintosh Adapter Windows 95/98 inf. Diskette USB Cable Limited Warranty 3 Years - Parts, Labor and CRT

F Series

The Multiscan FD Trinitron displays offer the very latest in advanced CRT display technology from Sony: the FD Trinitron CRT. These virtually flat CRTs minimize geometric distortion and reduce reflective glare that may cause eyestrain. Designed with the demanding CAD and graphic professionals in mind, the Multiscan F Series sets a new level of image performance, ease of use and reliability. The stunning images produced by this display are a result of Sonys new HiDensity Electron Gun with Enhanced Elliptical Correction System technology. The tight 0.22mm aperature grille pitch delivers sharp, detailed color images consistently across the entire screen especially in the corners. Digital Multiscan and Active Signal Correction (ASC) technologies allow for easy set-up, regardless of the input signal or resolution. And with broad horizontal scan rates available, resolutions as high as 1800 x 1440 @ 80Hz (F500) are possible. Our unique DisplayMouse control is easy-to-use and allows for precise manual adjustment of the image to fit individual user preference. Sony left nothing to the imagination with this display, including GeoLock Plus circuitry. This feature will automatically sense and neutralize electromagnetic fields that can cause image or color distortion, which is commonly noticeable on large screen displays. The F Series is designed for Windows 2000 and Windows 98, is Macintosh compatible and meets or exceeds all of the industry safety standards, including TCO 95 compliance.
Sony Electronics Inc. Information Technologies Marketing Division 3300 Zanker Road, San Jose, California 95134 For more information: 1.800.352.SONY Web address: http://www.sony.com/displays
Computer Interface: The computer industry lacks standards, and therefore, there are a multitude of varying software packages and add-on hardware options. This display is not manufactured to any specific software, and Sony does not and cannot make any warranty or representation with respect to the performance of this product with any particular software packages and/or non-Sony add-on hardware option except those mentioned in this document. Sony hereby disclaims any representations or warranty that this product is compatible with any combination of non-Sony products you may choose to connect. While Sony representatives or Sony authorized dealers may be able to assist you and may make recommendations, they are NOT authorized to vary or waive this disclaimer. Purchasers must determine for themselves the suitability and compatibility of the hardware and software in each and every particular instance. 1999 Sony Electronics Inc. All rights reserved. Reproduction in whole or in part without written permission is prohibited. Sony, the Sony logo, displays by sony, Multiscan, Trinitron, FD Trinitron, Digital Multiscan, HiDensity Electron Gun, GeoLock Plus, DisplayMouse, ASC and Enhanced Elliptical Correction System are trademarks of Sony. Microsoft, the Windows Logo and Windows 2000 are registered trademarks of Microsoft Corporation. Macintosh and Mac are trademarks of Apple Inc. Features and specifications are subject to change without notice. Non-metric weights and measurements are approximate. This monitor is Energy Star Compliant when used with a computer equipped with VESA Display Power Management Signaling (DPMS). As an International Energy Star Partner, Sony Corporation has determined that this product meets the International Energy Star Program for energy efficiency. The Energy Star emblem does not represent EPA endorsement of any product or service. D174 Printed in U.S.A. 01/99

Munsell Color Science Laboratory Technical Report
Colorimetric Characterization of Three Computer Displays (LCD and CRT)
Jason E. Gibson and Mark D. Fairchild January, 2000

Abstract

The colorimetric characterization of two flat-panel LCD displays, an SGI 1600SW and an IBM prototype, was evaluated and compared to that of a flat-screen CRT display, the Sony GDM-F500. The results showed that both the SGI and the Sony displays could be characterized using the traditional gain-offset-gamma (GOG) model. Some improvement for the SGI display was gained by using three 1D LUTs in place of the gamma correction step. The prototype IBM display however exhibited a significant failure of additivity and could not be characterized as well as the other displays at this time.
Munsell Color Science Laboratory Center for Imaging Science Rochester Institute of Technology 54 Lomb Memorial Drive Rochester, NY 14623-5604 USA

Introduction

Background
The basic procedure for characterizing a color CRT display using the gain-offset-gamma (GOG) model is given in [Berns 1996, Berns 93a, 93b]. In the basic implementation a fitted nonlinear function is first used to convert normalized digital counts {dr, dg, db} into linear scalars {R,G,B}. These scalars are then linearly combined via a 3x3 matrix and the internal flare added in. In some cases three 1D LUTs can be substituted for the nonlinear transfer functions. 1.2 Measurement Conditions
Colorimetric measurements were made using an LMT C1200 Colorimeter which gives readings in arbitrary units. Luminance measurements in cd/m2 were made using an LMT L1009 Photometer with a 1 aperture. Spectral Radiance measurements and additional luminance and spectral measurements were made using a Photo Research PR704 spectroradiometer. All colorimetric coordinates were determined using the CIE 1931 Standard Colorimetric Observer (2). Colorimetric errors are evaluated in terms of E*94 color differences with the standard parametric factors. Unless otherwise noted, all measurements were performed on a central 3.5" uniform square patch with the remainder of the display filled with a medium gray background represented by RGB digital counts of (128,128,128). This was done to simulate the load placed on the display during normal usage. As with all LCD displays, the appearance of both the SGI and IBM displays is angular dependent. To ensure a consistent evaluation of each display, all measurements were made at a 0 incident angle.
Display Specifications, Configuration, and Setup
This section details each of the three monitors tested. A table at the end of this section is provided for easy comparison of the major technical specifications of each display. 2.1 Sony GDM-F500
During this analysis this display was driven by an Apple Macintosh G3 computer at a resolution of 1280x1024 @80Hz. The white point was set at 6500K using the monitors built-in controls. Because most CRTs are sensitive to magnetic field variations, all measurements were taken without moving the display. The onboard degaussing feature was used several times before beginning measurements. Apples ColorSync software was set in a generic RGB mode during all phases of testing. 2.1.1 Product Features
The GDM-F500 is Sonys flagship model display for CAD and graphic professionals. This virtually flat 21" CRT uses the FD Trinitron tube. Other enhancements include: HiDensity Electron Gun which allows for a tight 0.22 mm aperture grille pitch. Enhanced Elliptical Correction System technology which uses additional focusing elements to correct for the elliptical beam shape distortions near the edges of the screen. GeoLock Plus circuitry which automatically senses and neutralizes electromagnetic fields thereby reducing image color distortion commonly noticeable on large CRTs. 1.1.2 Further Information
More information about this display can be found on Sonys web site: http://www.ita.sel.sony.com/products/displays/fseries/gdmf500.html. White papers containing more details on the various technologies used in this, and other Sony displays can be found at: http://www.ita.sel.sony.com/products/displays/displaytech.html. In this section: All rights reserved by Sony Electronics Inc. are trademarks of Sony Electronics Inc.

Silicon Graphics 1600SW Flat Panel Monitor
The 1600SW display was driven by a SGI Visual Workstation 320. The SGI ColorLock sensor and software was used to calibrate the display to the sRGB setting (D65 white point, gamma of 2.2) prior to making measurements. 1.1.1 Product Features
The 1600SW is an active matrix digital LCD, flat panel display with a SXGA-wide (1600 x 1024) format. Product features include: Adjustable white balance via software and dynamic backlight adjustment. Accurate to within 25K. ColorLock system which uses factory characterization data stored within the onboard memory of each monitor and a specially designed photopic sensor to self-correct the panel. 1.1.2 Display Defects
As with most LCD panels on the market today, defects are common due to high manufacturing costs. The most common defects are weak pixels and ones that are stuck in one state which appear as unchanging bright or dark spots depending on the display mode (normal bright vs. normal dark). Silicon Graphics allows no more that 5 green defects per monitor, with no more than a total of 8 bright defects of all colors combined. On the particular display used in this study (SN 92000350N), there are two noticeable on red pixels near the edge of the screen. 1.1.3 Viewing Angle
One of the major issues facing the designers of LCD displays is viewing angle. The pixels of an LCD display do not emit light (as in a CRT) but rather obtain it from a backlight source and transmit it along their molecular axes. Since the twisted-nematic liquid crystals exhibit birefringence, changes in viewing angle lead to changes in appearance. SGI defines the viewing angle of their displays to be the range of angles giving acceptable contrast ratios and linear gray scales. This display claims a viewing angle of 120 horizontal, +45/-55 vertical. From casual observation of the display, these values seems to be correct. 1.1.4 Further Information
More information can be found on SGIs web site at: www.sgi.com/peripherals/flatpanel A well written introduction to LCD display technologies, as well as the specific advances made in the SGI display can be found at: www.sgi.com/peripherals/flatpanel/whitepapers.html 3

Viewing Angle

The viewing angle of the IBM display very limited. Even small shifts in viewing position alter the appearance of the image. This is because no effort has been made to minimize the angular dependency in this prototype. A commercial version of the display would require much improvement in this area. 1.1.3 Further Information
Information about Roentgen can be found at: www.research.ibm.com/news/detail/factsheet200.html In this section: All rights reserved by IBM Inc. 1.4 Summary Comparison or in [Bassak 1998].
The table below lists the key features of each display for comparison. Table 2-1Summary Comparison of Display Physical Characteristics
Viewing Size Resolution Pixel Pitch Number of Pixels Bits per channel Luminance Weight
Sony GDM-F500 19.8 Diagonal ~72 ppi 0.22 mm 1280H x 1024V @80Hz cd/m2 (427:1 contrast) 70.5 lbs.
SGI 1600SW 17.3 Diagonal 110 ppi 0.231 mm 1600H x 1024V cd/m2 (276:1) 16 lbs.
IBM Roentgen 16.3 Diagonal 200 ppi 0.126 mm 2560H x 2048V cd/m2 (205:1) < 20 lbs.
Please note the following points: In this comparison, viewing size is defined as the diagonal size of the viewable area of the display. The number of pixels figure for the Sony CRT is the setting used for this evaluation, it is capable of many other configurations. Luminance measurements were made on a central 3.5" square surrounded by mid gray.

Spectral Characteristics

A useful property when characterizing a display is that of stable primaries. To examine the spectral stability of the displays primaries, a series of four logarithmically spaced patches {35,81,145,255} was displayed for each primary and measured with the PR704. A five step ramp, including black, was also measured. If the primaries were spectrally stable, the normalized plots of each ramp shown in the figures below would appear as a single curve. During the measurement process, every effort was made to keep the PR704 perpendicular to the display to minimize angular effects. At the distances used for measurement, the 0.5 circular aperture spanned approximately 20 pixels on the display. While the PR704 provided data from 380780nm at 2nm intervals, only the range from 400700nm was evaluated in this section. If the tristimulus values used in subsequent stages were to be calculated from this data it is suggested that the range be extended to at least 720nm to capture the red phosphor emission near 710nm [Berns 1993b]. Issues such as the tradeoff between bandpass and sampling increment must also be addressed. Since a very accurate colorimeter, the LMT C1200, was available which gives tristimulus values directly, these spectral measurements were made primarily for illustrative purposes.

The spectral radiance characteristics of the Sony display are shown in the figures below. Figure 2-1 shows the spectral radiance distribution of the white. Figure 2-2 shows the corresponding plot for the displays black. Plots of the normalized ramps are show in Figure 2-3 Figure 2-6 below. In these figures the solid line represents the full on primary {level 255}, and the broken lines the intermediate levels. Figure 2-1Sony Display White Radiance

White 5.0E-03

Radiance (W/m2sr)
4.0E-03 3.0E-03 2.0E-03 1.0E-03 0.0E+550 Wavelength (nm) 700
Figure 2-2Sony Display Black Radiance

Black 2.0E-05

1.6E-05 1.2E-05 8.0E-06 4.0E-06 0.0E+550 Wavelength (nm) 700
Figure 2-3Normalized Gray Ramp

Gray 1.0

Relative Power
0.8 0.6 0.4 0.2 0.550 Wavelength (nm) 700
Figure 2-4Normalized Red Ramp

Red 1.0

Figure 2-5Normalized Green Ramp

Green 1.0

Figure 2-6Normalized Blue Ramp

Blue 1.0

Based on the figures above, it would appear that the Sony display exhibits reasonable spectral stability as to be expected from a good quality CRT. From spectral measurements such as these, the purity of each channel can be readily evaluated. For example, the strong peak near 630nm from the rare-earth elements used in the red phosphor is visible in both the green and blue channels.
The corresponding measurements for the SGI display are given below. The white, shown in Figure 2-7, is characteristic of the fluorescent backlight utilized in this display. The non-zero radiance for the black state, Figure 2-8 (compare to Figure 2-2), is common for LCD displays as the polarizes are unable to fully extinguish the backlight and a small amount leaks through. Figure 2-7SGI Display White Radiance

White 1.2.E-02

1.0.E-02 8.0.E-03 6.0.E-03 4.0.E-03 2.0.E-03 0.0.E+550 Wavelength (nm) 700
Figure 2-8SGI Display Black Radiance

Black 3.0.E-05

2.5.E-05 2.0.E-05 1.5.E-05 1.0.E-05 5.0.E-06 0.0.E+550 Wavelength (nm) 700
Figure 2-9Normalized Gray Ramp
Figure 2-10Normalized Red Ramp
Figure 2-11Normalized Green Ramp
Figure 2-12Normalized Blue Ramp
The normalized plots of each channel appear to have greater variability than was seen in the Sony monitor, especially in the blue. Furthermore, the characteristics of the fluorescent backlight are visible in all three channels.

Measurements on the IBM display follow. Again, the characteristics of the fluorescent backlight are clearly visible from the white shown in Figure 2-13. Figure 2-13IBM Display White Radiance
White 1.4.E-02 1.2.E-02 1.0.E-02 8.0.E-03 6.0.E-03 4.0.E-03 2.0.E-03 0.0.E+550 Wavelength (nm) 700
Figure 2-14IBM Display Black Radiance

Black 8.0.E-05

6.0.E-05 4.0.E-05 2.0.E-05 0.0.E+550 Wavelength (nm) 700
Figure 2-15Normalized Gray Ramp
0.8 0.6 0.4 0.2 0.550 Wavelenght (nm) 700
Figure 2-16Normalized Red Ramp
Figure 2-17Normalized Green Ramp
Figure 2-18Normalized Blue Ramp

2.4 2.4.1

Summary Comparison Peak Spectral Radiance
Table 2-1 compares the peak spectral radiance output of each display for white, black, and the primaries. The two LCD displays have higher peak radiance in all three channels than the conventional display, due in part to the use of the narrow-band fluorescent backlights. Table 2-1Peak Spectral Radiance Values for Each Display Peak Radiance (W/m2sr)E-03 White Point Black Red Green Blue 2.4.2 Sony 3.94 0.02 3.83 0.75 0.83 SGI 10.9 0.03 5.5 8.8 3.4 IBM 12.0 0.07 8.2 11.0 2.4
Spectral Variability. ) were
To summarize the observed deviations from stability, coefficients of variation ( CV =
computed. That is, at each wavelength (400700nm, 2nm), the standard deviation and average of all four (or five) normalized measurements at that wavelength was computed and the ratio taken. The average of all 151 CVs for each ramp is shown in Table 2-2. By normalizing the standard deviation with the mean, CVs are directly comparable across changes of magnitude. Table 2-2Spectral variability-Average CV over wavelength Gray Red Green Blue Sony 0.20 0.35 0.32 0.57 SGI 0.34 0.81 0.72 0.72 IBM 0.19 0.84 0.69 0.63

LCD backlight Comparison

Examining Figure 2-19, it appears that the SGI and IBM display use a similar fluorescent back light, with the SGI display having slightly more output in the blue end of the spectrum. Since the IBM display is a prototype unit designed for testing the new LCD, a standard back light was used. It is possible with some optimization of the backlight and filters used that the IBM display could be improved.
Figure 2-19Backlight Comparison of IBM and SGI displays

1.4E-02 1.2E-02

Radiance(W/m2sr)
1.0E-02 8.0E-03 6.0E-03 4.0E-03 2.0E-03 0.0E+550 Wavelength (nm) 700 IBM SGI

Temporal Stability

Both CRT and LCD displays require time to reach a steady state from a cold start. While no specific warm-up tests were run for the displays evaluated in this report, the characteristics observed by Fairchild [1998] can reasonably be expected for the LCD displays. To ensure that the display had reached a steady state, each display was left for over four hours before beginning measurements. Since the measurement process involved several repeat presentation of each primary over the course of several hours, a post hoc evaluation of the temporal stability can be preformed. Table 3-1 below shows the E*94 mean color difference from the mean (MCDM) for each primary. The time span for these measurements is over three and a half hours for each display. Table 3-1Temporal Stability of each Display Red Green Blue Sony 0.13 0.14 0.08 SGI 0.06 0.05 0.04 IBM 0.05 0.04 0.03
The results indicate that the two LCD panels were very stable over the time of measurement and therefore were given adequate warm-up time prior to starting. The slightly larger variability seen on the CRT is not surprising and is small enough to be of little concern.

Spatial Independence

Spatial independence refers to the impact that a color displayed on one area of the monitor has on a color in another area. Characterizing a display that does not exhibit this property is difficult if not impossible. To test the spatial independence of each display, a series of nine color stimuli were measured on nine different background made up of the same nine colors for a total of 81 colorimetric measurements [Fairchild 1998]. The CIELAB coordinates of each stimulus were then computed using the average value of white on gray as the CIELAB reference white. The data are summarized in Table 4-1 for each display using mean color-difference from the mean (MCDM) metrics in terms of CIE94 color differences. The MCDMs were calculated both across background (i.e. how did the nine different backgrounds affect each of the foreground colors), and across stimuli (i.e. how much did the nine different foreground colors change on a given background). The data in this section were not flare corrected since only changes are compared. Table 4-1MCDMs for Spatial Independence Measurements Color Black {0} Gray{128} White {255} Red {128} Red {255} Green {128} Green {255} Blue {128} Blue {255} Sony Background Stimuli 0.76 1.67 0.18 0.53 1.68 0.44 0.42 0.64 0.52 0.32 0.53 0.32 0.44 0.26 0.63 0.92 0.38 0.43 SGI Background Stimuli 0.10 0.03 0.07 0.26 0.14 0.07 0.08 0.05 0.06 0.04 0.09 0.12 0.05 0.03 0.08 0.07 0.06 0.05 IBM Background Stimuli 0.15 0.13 0.15 0.48 0.17 0.25 0.23 0.23 0.22 0.13 0.19 0.31 0.28 0.12 0.19 0.14 0.27 0.06

The overall MCDM for the SGI display was 0.08, 0.21 for the IBM, and 0.62 for the Sony display. Given that each pixel in an active-matrix TFT-LCD is physically distinct from its neighbors, good spatial independence was expected. In a conventional CRT, a single scanning electron beam is used to address each pixel of a given color and they often suffer from poor spatial independence.

Luminance & Contrast

Using the LMT L1009 photometer, the luminance of each primary, black, and white was measured. The contrast of the display was then calculated by taking the ratio of the white to the black. Results are summarized in the tables bellow. The targets were displayed as both full-screen colors, Table 5-1, and as 3.5" squares with gray surround, Table 5-2, for comparison. The large difference in values point to the need for carefully defining the measurement conditions before stating results. Table 5-1Measured Luminance and ContrastFull Screen Color Red Green Blue White Black Contrast (W/K) Sony (cd/m2) 15.47 36.0 3.51 55.8 0.004 13950:1 SGI (cd/m2) 44.5 110.3 13.81 167.8 0.541 310:1 IBM (cd/m2) 38.3 93.9 11.92 150.7 0.665 227:1
Table 5-2Measured Luminance and Contrast3.5" Square with Gray Surround Color Red Green Blue White Black Contrast (W/K) Sony (cd/m2) 15.70 39.3 3.96 55.9 0.131 427:1 SGI (cd/m2) 42.9 106.4 13.34 161.5 0.584 276:1 IBM (cd/m2) 38.4 94.5 12.19 152.7 0.745 205:1
Comparing the two tables above, it can be seen that the two LCD panels maintained their black level, and therefore contrast as the target size was reduced. Given the nature of the LCD display, it is expected that this would hold even for very small targets. In comparison, the CRT had an extremely large contrast with a full screen measurement, but a more moderate contrast when the target was reduced in size. Reducing the target size further would cause still more reduction in contrast.
The full screen luminance of the Sony monitor is more than a factor of two lower than either of the two LCD displays tested but is typical of most good quality CRT displays. The full screen contrast ratio however was quite high for the Sony display. When properly setup, little to no light is emitted from the black state on a CRT. 5.2 SGI
The SGI monitor has the highest luminance output of the thee monitors tested in this report. While not as high luminance as the Apple Studio display measured by Fairchild [1998] which measured 188 cd/m2, the SGIs contrast ratio was considerably higher (310:1 vs. 250:1) indicating a darker black level. The measured contrast ratio is on par with the manufactures claim of 350:1. To achieve this SGI uses two techniques. First, a negative birefringence compensation film is placed after the liquid crystal cell to compensate for the positive birefringence introduced by the liquid crystal giving a greater extinction level. Second, thick color filters are used to maintain high saturation levels in the primary color subpixels thus minimizing the impact of any stray leakage from adjacent pixels. 5.3 IBM

The weaker performance of the IBM display is most likely due to its prototype nature and will be likely be improved upon in the commercial version.
Chromaticity Constancy of Primaries
The gain-offset-gamma (GOG) model for characterizing displays uses a two stage process. First, three 1D-LUTs are used to transform the incoming digital counts into linear scalars. Second, the linear scalars are multiplied by a 3x3 primary mixing-matrix. Thus the estimated signal is a scaled version of the full strength primaries. For this process to work, the chromaticity coordinates of each level must remain constant. To test this assumption, a series of 16 logarithmically spaced steps in red, green, blue were measured along with a 17 log-step gray ramp. As discussed by Fairchild [1998], the black level flare has been removed from each measurement before computing the chromaticities. Results for each display are given below. 6.1 Sony
Figure 6-1Chromaticity of Red, Green, Blue Primaries and Neutrals

0.7 0.6 0.5 0.4

0.3 0.2 0.1 0.0 0.0 0.1 0.2 0.3 x 0.4 0.5 0.6 0.7
The primary constancy of the Sony display appears adequate, as is expected of a high quality CRT. The tendency of each primary towards the white point may indicate that some residual flare was not accounted for. The large variation in the gray levels is due primarily to the undefined nature of chromaticity coordinates at very low tristimulus values.
Figure 6-2Chromaticity of Red, Green, Blue Primaries and Neutrals
The SGI display appears to exhibit good consistency in the primaries and has a stable gray scale. The one outlying point in the gray ramp is the black. The tristimulus values of the black patch, after subtracting the average flare value, were slightly non zero {-0.001, -0.0008, -0.0007} and therefore produced an outlying point in chromaticity space rather than being undefined if it measured {0,0,0}. In practice these small deviations from zero are insignificant and would be removed, their inclusion here is simply illustrative.
Figure 6-3Chromaticity of Red, Green, Blue Primaries and Neutrals

0.7 0.6 0.5

0.4 0.3 0.2 0.1 0.0 0.0 0.1 0.2 0.3 0.4 x 0.5 0.6 0.7 0.8

Summary Comparison

To summarize the variability of each displays primaries, Table 6-1 lists the coefficient of variation in both the x and y dimensions for each primary. Table 6-1Chromaticity Variability Color Red Green Blue Gray x 0.01 0.01 0.06 0.09 Sony y 0.00 0.03 0.31 0.01 x 0.01 0.01 0.01 0.02 SGI Y 0.01 0.01 0.15 0.01 X 0.01 0.02 0.08 0.03 IBM Y 0.02 0.01 0.07 0.02

Additivity

The additivity of each display was evaluated in both luminance, Table 7-1, and tristimulus space, Table 7-2. Luminance values were measured with the LMT L1009 photometer at a distance such that its 1 spot size spanned approximately 20 pixels on the display. The LMTC1200 colorimeter used for tristimulus measurements has a 3" diameter aperture and is set 2.25" back from the front surface of the device by means of a matte black tube. All tristimulus values in this section were flare corrected by subtracting the average tristimulus values of the black squares measured (8 in all) from the corresponding values of each sample. Results for each display are discussed in the various subsections below. Table 7-1Luminance Additivity Color Sony (cd/m2) R+G+B 54.98 White 55.8 Difference 1.5% SGI (cd/m2) 168.61 167.8 -0.5% IBM (cd/m2) 144.12 150.7 4.5%
Table 7-2 Tristimulus Additivity Value White Sony R+G+B 35.53 36.70 32.77 % Diff. 0.70% 0.63% 1.46% White 84.83 87.40 69.02 SGI R+G+ B 84.82 87.33 68.96 % Diff. 0.01% 0.08% 0.09% White 75.92 81.32 41.46 IBM R+G+ B 70.14 75.21 40.22 % Diff. 7.61% 7.51% 2.98%

X 35.78 Y 36.94 Z 33.26

The small failure of additivity for this display might well be due to a small increase in flare at the high luminance levels which is not present when estimating the flare from black alone. There may also be circuitry on board the display which increases power sent to the electron guns to compensate for their increased load. The degree of additivity is sufficient to justify the use of a 3x3 primary matrix transform. 7.2 SGI

The additivity on this display was excellent, exceeding many other displays we have tested. Given the high resolution of this display and the discrete nature of each pixel, it is not surprising that the additivity was good. The use of the 3x3 primary matrix transform is well justified. 7.3 IBM
The large differences between white and R+G+B are disturbing. A possible cause may be the strong angular dependency of this display. The LMT colorimeter was used with a very large acceptance cone and may therefore be subject to color shift errors. However, a substantial failure of additivity was also observed using various aperture sizes both with the LMT photometer and the colorimeter as shown in the table below. This issue is still under investigation. Table 7-3 Additivity vs. Aperture Size LMT Colorimeter Color Red Green Blue R+G+B White % Difference X 37.84 21.34 5.988 65.16 70.6 7.7% 3" Aperture Y Z 19.279 0.263 45.069 3.403 5.439 33.62 69.787 37.29 75.509 38.55 7.6% 3.3% 1" Aperture X Y Z 3.764 1.916 0.027 2.121 4.494 0.34 0.61 0.543 3.417 6.495 6.953 3.784 7.004 7.482 3.862 7.3% 7.1% 2.0% 0.5" Aperture X Y Z 0.749 0.381 0.005 0.421 0.892 0.066 0.121 0.108 0.675 1.291 1.381 0.746 1.385 1.483 0.76 6.8% 6.9% 1.8%
Table 7-4 Additivity vs. Aperture Size LMT Photometer Color Red Green Blue R+G+B White 6' 36.5 88.8 11.6 136.9 143.3 Aperture Size 20' 1deg 36.6 36.6 89.0 88.8 11.60 11.58 137.2 136.98 143.5 143.3 3deg 36.4 88.2 11.54 136.14 142.4 26

%Difference

Electro-Optical Transfer Functions
Being a conventional CRT display, the standard GOG model was used to characterize the Sony display. From a 17 step, logarithmically spaced gray ramp, target RGB scalars were estimated using the inverse 3x3 mixing matrix. Then, using a simplex nonlinear estimation, a constrained GOG model was fitted using Equation 8-1. The estimated parameters are given in Table 8-1, and the resulting curves are plotted in Figure 8-1Figure 8-3. Equation 8-1GOG Model Constrained to Gain+Offset=1.0

d = Gain c + ( Gain )

Where: refers to the red, green, or blue scalar (RGB).
Table 8-1Estimated GOG Parameters for Sony Monitor Channel Gain Gamma Red 1.0025 1.6553 Green 1.0200 1.7052 Blue 1.0200 1.7581 To test the fit of this model, the training data was estimated and the E*94 difference computed. Average error was 0.61, with a maximum of 1.13. A test with independent data is given in 9. Figure 8-1Measured Data and Fitted GOG model for the Red-channel

1.0 0.8 0.6 0.4 0.2 0.0.2 0.4 0.6 0.normalized digital count
Figure 8-2Measured Data and Fitted GOG model for the Green-channel

1.0 0.8 0.6

0.4 0.2 0.0.2 0.4 0.6 0.normalized digital count
Figure 8-3Measured Data and Fitted GOG model for the Blue-channel
Both a conventional GOG model using a 17 step neutral ramp, and a cubic spline interpolation of three 52 step ramps (red, green, blue) were used in modeling the SGI display. The estimated parameters of the GOG model are shown in the table and graphs below. Table 8-28-3Estimated GOG Parameters for SGI Display Channel Red Green Blue Gain 0.6706 0.8000 0.9507 Gamma 4.4622 3.2559 2.2841
The low estimated gain terms indicate a poor dark state. Preferably, the gain terms should all be slightly greater than 1.0 which creates negative offsets (offset = 1.0 - gain) and ensures that no light is being emitted at the black level. As with the Sony display, the fit of each model was evaluated by re-estimating the training data. Results for the two models tested for the SGI are shown in Table 8-4. An independent data set is evaluated in 10. Table 8-4Redistribution Errors for SGI Models Model GOG LUT Average E*94 2.94 0.97 Maximum E*94 6.72 2.2 Number of Points measured 17 logarithmically spaced gray patches 52 steps each for RGB, 156 total
Figure 8-4Measured Data and Fitted GOG model for the Red-channel
1.0 0.8 0.6 0.4 0.2 0.0.2 0.4 0.6 0.normilized digital count
Figure 8-5Measured Data and Fitted GOG model for the Green-channel
Figure 8-6Measured Data and Fitted GOG model for the Blue-channel
0.4 0.2 0.0.2 0.4 0.6 0.normilized digital count
Although the GOG model fit the low end reasonably well, the systematic trends to overestimate the high end indicated that this model might not perform well. Therefore, a set of three 1D LUTs were created from the 52 step primary ramps using cubic-spline interpolation between the nodes. The resulting transfer curves are shown below. Figure 8-7Measured Data and LUT for the Red-channel

11 References

Gill Bassak, As Fine as the Eye Can See, IBM Research Magazine, 36, (1998). Roy S. Berns, Methods for characterizing CRT Displays, Displays, 16, 173-182 (1996). Roy S. Berns, Ricardo J. Motta, Mark E. Gorzynski, CRT Colorimetry. Part I: Theory and Practice, Color Res. and Appl., 18, 299314 (1993a). Roy S. Berns, Ricardo J. Motta, Mark E. Gorzynski, CRT Colorimetry. Part II: Metrology, Color Res. and Appl., 18, 315325 (1993b). H.E. J. Neugebauer, Quality Factor for Filters Whose Spectral Transmittances are Different from Color Mixture Curves, and Its Application to Color Photography, JOSA, 46, 821824 (1956).