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    Testing and Evaluating Displays and Projectors    
Copyright © 1990-2011 by DisplayMate Technologies Corporation. All Rights Reserved.
This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated
into any other work without the prior written permission of DisplayMate Technologies Corporation.

The following are detailed guidelines for testing and evaluating displays, projectors and other imaging devices. Accompanying articles provide specific information and analysis for Testing and Evaluating CRTs and Testing and Evaluating LCDs.

1. Use a high image quality video board and don't use a laptop:
For display evaluation and testing you need to start with the highest image and signal quality. There are substantial differences in the image quality produced by different video boards. Note that in general, laptops and PCMCIA cards do not produce very good image quality because they are optimized for size and power consumption. See the DisplayMate Best Video Hardware Guide for video board recommendations. Note that we recommend different video boards for LCDs and CRTs, as well as for analog and digital outputs.

2. Carefully select your test area:
Make sure that you have good clean AC power. Devices that give off magnetic or electromagnetic fields may adversely affect image quality. Keep "black box" transformers, speakers, fluorescent lights, and other electrical devices with transformers, motors or solenoids away from the displays, video cables and video boards. If you are testing CRTs, don't use a steel table or desk and keep away from building steel beams and other magnetic materials. Additionally, CRTs may need to be separated from one another to prevent magnetic interference. If you are testing LCDs, viewing angle is critical, so make sure that you have a straight-ahead direct view of each display.

3. Use a dark room for your tests and evaluations:
Use a relatively dark room for testing in order to maximize your sensitivity to subtle visual effects and problems. The darker the better. Avoid fluorescent lighting because it produces more flicker than incandescent lighting. For some tests like Black-Level and Stuck Pixels the room should be pitch black. Otherwise it should be very dark, much darker than a normal viewing environment in order to make sure that you don't overlook anything.

4. Don't use extension video cables:
Use the shortest manufacturer supplied video cables. Don't use extension cables under any circumstances as they degrade image quality, often substantially. Note that for short 2 meter/6 foot runs there is generally no difference between a single DB-15 VGA input cable and 5-cable BNC inputs.

5. Reset the display and video board:
Unless this is a brand new unit out of a sealed factory fresh box you will need to activate the factory reset button or buttons in order to restore all of the default settings. This applies to both the display and video board.

6. Warm up for at least 30 minutes:
All displays and video boards take time to warm up for stable optimum performance. During this time everything changes: brightness, contrast, even video bandwidth.

7. Thoroughly degauss CRT displays:
CRT displays that have been moved may take more than a single degauss cycle to fully normalize. If there is a manual degauss button press it several times, waiting at least 15 minutes between each cycle. Otherwise, simply turn the display off and then right back on several times, again waiting at least 15 minutes between cycles. If you don't wait enough time between cycles the degauss operation will not be fully effective.

8. Special considerations for projectors:
If you are testing projectors it is especially important that you use a totally dark room because of the lower surface brightness. Projectors tend to have light leaks from different areas so map them out. There will also be stray light that extends beyond the image area. Also watch out for spurious reflections off projector stands, tables, walls, etc. Keep the projected images from adjacent projectors well separated so that stray light from one projector doesn't contaminate the image of another. The output from projection bulbs generally changes over time in both intensity and color, so either use a brand new bulb or carefully note its age. Be sure to use a high quality projection screen. See the DisplayMate Best Video Hardware Guide for screen recommendations.

9. Set the color depth and refresh rate:
All tests should be done in 24/32-bit True Color modes. Don't use 16-bit High Color modes because of the coarse gray-scale and green cast they impart to the gray-scale. For the refresh rate we recommend 75 Hz for CRTs and 60 Hz for LCDs. Image quality degrades as you increase the refresh rate. Always use the lowest refresh rate that doesn't produce visible flicker. For earthlings the above values are generally optimum.

10. Set the resolution:
LCDs should be tested at the native resolution of the panel first. Then test their scaling engines for both higher and lower resolutions. Note that scaling generally results in a significant degradation of image quality, particularly for fine text and graphics. For CRTs, the optimum resolution depends on the application and screen size: typically 1024x768 for 17" and 19" displays or 1280x1024 for 19" and 21" displays. 21" displays are often used at higher resolutions such as 1600x1200, 1800x1440 and 2048x1536. The optimum resolution for a particular CRT may be affected by the relative strengths of the Moiré patterns at different resolutions.

11. Testing right out of the box:
We strongly recommend that that you set up all of the display controls before beginning your tests because of differences among video boards. However, if you want to test right out of the box with the absolute minimum number of adjustments, then set brightness and contrast at the very least. For LCDs using an analog input the automatic pixel tracking/phase control seldom produces the optimum setting, so also run your tests after setting manual pixel tracking/phase. Note that we recommend different video boards for analog input LCDs. See the DisplayMate Best Video Hardware Guide for video board recommendations.

12. Test and evaluate the displays simultaneously:
If possible run the tests on all the displays simultaneously side-by-side. That way even subtle differences that might be overlooked or forgotten become obvious. The best way to do this is to use identical multiple computer set ups, one for each display and controlled by a keyboard-mouse multiplexer. Almost as good is a high quality mechanical switcher that allows you to rapidly switch between displays, but with only one display active at a time. An excellent compromise is a high quality multi-output distribution amplifier. With it you can compare the displays simultaneously for all tests except Video Bandwidth, Streaking, Ringing and Overshoot. For these latter tests you'll need to directly connect each display to the video board one-at-a-time. See the Recommended Display Test Equipment section below.

13. Use a Reference Display:
Include one or more Reference Displays in your evaluations, which are used as standards for image quality, gray-scale and color accuracy. One Reference Display should be a high quality CRT monitor, which is used to determine color and gray-scale accuracy, and is also free from motion artifacts (if you are testing with the DisplayMate Multimedia with Motion Edition). A second Reference Display should be a top performer in the technology and category that you are testing. See DisplayMate's Best Video Hardware Guide for recommended Reference Displays.

14. Set up the display by adjusting ALL user controls:
Carefully go through the DisplayMate "Set Up Display" selection first and adjust ALL user controls for each display before beginning your evaluations. Note that many controls interact with one another so that you many need to go through the procedure more than once. For analog input LCDs you should periodically check and readjust pixel tracking/phase and note which displays are more or less stable than others. For CRTs carefully adjust Moiré reduction and then check the sharpness and resolution.

15. Drift:
Many display parameters vary over time, particularly as the display warms up. Even after that some parameters may continue to vary over a period of hours. The best displays will have the least drift. Almost anything may vary, but black-level, pixel tracking/phase, Moiré, and the white-point color temperature are the most common.

16. Test and evaluation suites:
If you are using the DisplayMate Multimedia Edition run one of the specialized test scripts for the type of display you are testing. Otherwise begin with the DisplayMate Video Obstacle Course selection that is included in all DisplayMate products.

17. Instrumentation or the human eye:
Using the human eye for evaluation rather than instrumentation is preferred because that is exactly what all end users will be using. The large library of specialized DisplayMate test patterns provides very high sensitivities to all display parameters and imperfections, thereby making the subtleties of display performance obvious to the eye. The suites of DisplayMate patterns make this process both systematic and analytical. While instrumentation produces precise numbers, they often do not respond in the same way as the human eye, so the results are precise but inaccurate. In addition, the instrumentation must be calibrated and the numerical results still require "subjective" evaluation and interpretation. Finally, all advanced DisplayMate products include special test patterns designed for use with instrumentation, should you need or want to use them. One piece of instrumentation that we strongly recommend is a color analyzer with photometer. They are pre-calibrated for the human eye visual response and accurately and precisely measure colors and intensities. See the Recommended Display Test Equipment section below.

18. Quantitative evaluations:
The image quality of each test pattern should be evaluated on a numerical scale of, for example, 1 to 5, with 1 as poor and 5 as excellent. If you are evaluating all of the displays simultaneously, another scheme is to rate each display according to its pecking order in image quality for each test pattern, with number 1 the best. In that case, low score wins, like in golf.

19. Weighting your results:
After you've scored each test pattern it's still necessary to combine all the numbers into a single index of merit. Some test patterns are more important than others so a straight average is not the best method in our opinion. How to weight the importance of each pattern is an editorial value judgement that each reviewer or organization needs to make. Be sure to explain your methodology.

Recommended Display Test Equipment

If you are an end user and want to test and evaluate displays all you really need is DisplayMate for Windows Standard or Video Editions. If you are a journalist, corporate evaluator, test lab, or manufacturer then the following equipment is highly recommended. For journalists, note that many manufacturers will loan equipment in return for an editorial mention within the article.

  • Test Patterns and Video Diagnostics:
    These two complementary DisplayMate products provide the most powerful display and video hardware testing and evaluation tools available:

    Our most comprehensive set of test patterns together with a Motion Engine to test for motion artifacts.
    DisplayMate Multimedia with Motion Bitmaps Edition

    This DOS based DisplayMate includes video system hardware diagnostics not available in our Windows based products.
    DisplayMate Professional for DOS

  • Spectroradiometer:
    For the accurate measurement of luminance, brightness, black level, contrast, chromaticity coordinates, color temperature, viewing angles, reflectance, and other photometric properties with the DisplayMate Multimedia Edition, this Spectroradiometer has a narrow one-degree acceptance angle.
    Konica Minolta   |   CS-200

  • Video Boards:
    For display evaluation and testing you need to start with the highest image and signal quality video boards. Note that we recommend different video boards for LCDs and CRTs, as well as analog and digital outputs.
    DisplayMate Best Video Hardware Guide - Video Boards

  • Reference Displays:
    It is very important to see how a display you're testing and evaluating compares with the very best display in its category.
    DisplayMate Best Video Hardware Guide - Displays

  • Digital HDMI / DVI Switcher and Distribution Amplifier:
  • Analog RGB Switcher and Distribution Amplifier:
  • Analog Component Video Switcher and Distribution Amplifier:
  • S-Video Switcher and Distribution Amplifier:
  • Composite Video Switcher and Distribution Amplifier:
    It is essential to test, evaluate, and compare multiple displays and projectors simultaneously with multiple signal sources.
    DisplayMate Best Video Hardware Guide - Video Electronics

  • Video Cables:
    Very high quality cables are especially important for display testing and evaluation. Keep all cable runs as short as possible. For analog signals, 2 meters/6 feet is best, but go no longer than 4 meters/12 feet.
    DisplayMate Best Video Hardware Guide - Video Cables

  • Optical Magnifiers:
    For examining individual pixels on screen at different magnifications.
    Edmund Scientific   |   5X, 10X, 50X Magnifiers

  • Cloth Tape Measure:
    Measure distances on the screen in millimeters.
    Find it at your local supermarket.

  • Book Night Reading Light:
    Lets you write notes in the dark.
    Find it at your local bookstore.
Copyright © 1990-2011 by DisplayMate Technologies Corporation. All Rights Reserved.
This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated
into any other work without the prior written permission of DisplayMate Technologies Corporation.

Copyright © 1990-2014 by DisplayMate® Technologies Corporation. All Rights Reserved.
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