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 | CRT monitors |
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| Test bed and calibration |
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CNET Labs' CRT test bed consists of a 733MHz Pentium III-based Dell Dimension 4100 desktop equipped with an Nvidia GeForce4 Ti 4600 graphics card and running Windows XP Professional SP2. We test all CRT displays at the manufacturer's recommended resolution, but we also note the display's output quality at both lower and higher resolutions.
We are currently in the process of upgrading our test bed to a desktop equipped with a 3.4GHz Pentium 4 550 processor, 1GB of DDR2 SDRAM running at 533MHz, an evga e-GeForce 7800 GTX KO PCI-Express graphics card with 256MB of memory, a 74GB Western Digital WD740 Raptor hard drive, and Windows XP Professional SP2. All displays tested after November 8, 2005 are tested in both test beds, but official results are reported only for displays tested using the Dell Dimension 4100 until our test bed upgrade is complete.
Parameters such as the default gamma-correction setting of a computer's operating system, the system's graphics card, the brand of phosphors used by the display's manufacturer, and the display's lighting environment all affect the image quality of a CRT monitor. As such, we adjust each display to perform optimally in the viewing conditions of our imaging lab, using manufacturer-recommended or Windows' default settings when possible.
| DisplayMate tests |
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With help from DisplayMate Technologies, we run through our own scripted selection of test screens in DisplayMate Multimedia Edition. These screens help us isolate common phenomena such as flicker, moiré, bounce, ghosting, and convergence errors. We break down our own analysis into five categories: focus, regulation, geometry, color quality/uniformity, and moiré and interference. The product's scores in each category are compiled and averaged to produce a single performance rating. The ratings you see in our reviews are a composite of the battery of individual screen analyses we run for each monitor.
The test screens described below represent many of our core CRT tests. Many of the test screens can be configured in a number of different ways, such as altering the background and foreground colors. Depending on the characteristics of an individual display, we might use several variations of these screens as well as additional DisplayMate screens not listed below.
| Resolution tests |
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Horizontal line resolution (screen 7:04)
This screen contains five horizontal bars composed of vertical white lines in varying frequencies of lines per inch. Higher line frequencies demand more from the display's resolution capabilities. We use this screen both to adjust the sharpness of the monitor and to evaluate its horizontal-resolution capabilities.
Vertical line resolution (screen 7:11)
This screen contains five horizontal bars composed of horizontal white lines in varying frequencies of lines per inch. Higher line frequencies demand more from the display's resolution capabilities. We use this screen both to adjust the sharpness of the monitor and to evaluate its vertical-resolution capabilities.
Focus matrix (screen 7:20)
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Page of text (screen 7:2)
This screen allows us to examine the display's ability to render text under a variety of conditions. With it, you can cycle through various text and background colors, view split screens with inverse text and background colors, and alter the type and the size of a font. We find it especially useful in evaluating a display's ability to render antialiasing enhancements.
Geometric linearity (screen 6:13)
This screen is typically used to check for geometric distortion, but we have also found it useful for focus testing, especially when shifting between resolutions. It's composed of a simple grid that can be rendered in varying densities.
| Video bandwidth and streaking tests |
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Screen regulation (screen 6:28)
This screen helps detect image contraction and expansion with strong changes in brightness. It displays a large, flashing square against a black background. The square can be assigned various colors, but white is generally the most useful. On a poor-quality CRT, the square appears to grow slightly as it flashes.
Video bandwidth index (screen 7:18)
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Midrange streaking (screen 10:46)
As the title suggests, this screen allows us to check the display's propensity for streaking and ghosting, light or dark shadows that trail an image in areas where large changes in intensity are present. You may detect this on your own monitor when it renders large, chunky graphics elements such as bar graphs or tiled arrangements of open windows.
| Geometry tests |
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We use this screen to determine the degree to which the screen's image and the display's bezel are capable of being brought into alignment.
Corner circle matrix (screen 6:22)
This screen contains nine circles arranged in three rows across the screen. The circles can be set to cycle through six different sizes in several different colors. We typically use this screen with black background and white foreground colors and set the circles at their largest size, variation 1. If the circles in the corners are elongated or squashed and cannot be corrected, then the CRT has geometry flaws.
| Color tests |
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Color scales (screen 9:41)
The color-scales screen illustrates a CRT's capacity to render gradations of colors smoothly, uniformly, and consistently. This screen is also used to check that the colors don't shift hue as the color levels increase or decrease.
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This screen helps us test the range of colors that a particular CRT monitor can produce through different forms of color mixing.
Extreme grayscale bars (DisplayMate screen 9:25)
As the title suggests, this screen has the dual function of evaluating the darkest and brightest areas of the grayscale. We use this screen primarily for the dark end of the scale to check a CRT's ability to deliver a true black and still produce the darkest grays of the grayscale.
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Similar to the testing of the dark end of the grayscale, we use this screen for checking and adjusting the bright end of the scale. We evaluate a CRT's capacity to produce all of the lightest grays of the grayscale while maintaining a bright white background.
| Moiré and interference tests |
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Moiré montage and moiré patterns (screens 7:29 and 7:30)
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Background noise and interference (screen 10:3)
We examine this screen for miscellaneous things that shouldn't be there. These may include irregularities relating to noise exacerbated by poor-quality cables or other problems associated with the electronics of the display.
