General
This is a collection of test patterns which can be used to investigate CRT monitor performance. The guide attached and the test patterns itself do not necessarily give an absolute answer of the performance of your monitor. They are intended to be used for comparison of monitors. Before starting
let the monitor warm up for 20 min.
demagnetize the monitor
- Geometry
With geometry test pattern you may estimate the geometric distortion of the picture. Following adjustments can be used to enhance the geometry of the picture: Width, Height, Horizontal centering, Vertical centering, Tilt, Trapezoid, Orthogonality, Pincushion, Pincushion balance
- Brightness and contrast
Brightness together with contrast is used to set the light output of the screen. Brightness determines the low light output level (black level) of the screen. It is better to set the black level low and lose some of the darker tones of gray than to set it too high and lose good contrast and black background.
Contrast adjust the brightness difference between light and dark tones. In other words, contrast adjusts the gain of the video amplifier. After setting the black level by adjusting brightness, the contrast control is used to set the light output of the screen to a comfortable level.
Note
Using a low level of contrast prevents eye fatigue.
Brightness has an effect on the picture focus. If there is excessively brightness in the picture, it may lose some of its details.
- High voltage regulation
High voltage is needed in the CRT monitor to accelerate the electrons of the electron beam which scans the screen. Bright areas on the screen load the high voltage source and may cause a drop in the voltage. This in turn enlarges the picture.
- Color
The user can not normally adjust white uniformity or brightness uniformity. White balance (color temperature) is often user adjustable.
- Convergence
A white line on the screen is made up of red, green and blue lines. If there are no convergence errors on the picture, the lines will be exactly overlaid and the resulting color is white.
If there is a serious convergence error, separate red green and blue lines will be seen instead of white.
Colored areas will show edges with wrong color.
In principle convergence means the ability of the monitor to correctly align red, green and blue components of an image on the screen.
Note
Vertical convergence error can be seen in horizontal lines or edges and vice versa.
- Picture clarity
Precondition for good picture clarity is a display mode with resolution high enough. Following factors may reduce the optimum picture clarity
Poor focus
Moire
Jitter
- Focus
The picture is made up by an electron beam scanning the screen. If the beam is sharp when it hits the phosphor, the picture has good focus. Focus is normally adjusted in the factory.
- Moire
Moire is a pattern thet may appear on all monitors. It can be seen as regular wavy distortion pattern in the picture. Moire is caused by intereference between CRT mask and the display mode resolution. In addition to display mode, certain types of pictures are even liable to moire. Generally monitors with good focus are prone to moire.
- Jitter
Jitter is a small movement the picture pixels may show in an otherwise still picture. The picture seems to be alive.
- Sound test
The test sound can be heard first in the left hand loudspeaker. The sound moves then gradually to the right hand loudspeaker.
