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Thread: Philips 107P50?
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17th May 2004 08:59 #1Registered User
Join Date: Apr:2004
Location: Burgas
Posts: 19
Philips 107P50?
, . 1024768/100Hz. , . 12801024 , . . ?
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17th May 2004 09:31 #2
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Contour Lines on High Resolution Monitors - Moire
These fall into the category of wavey lines, contour lines, or light and dark bands even in areas of constant brightness. (Some people may refer to this phenomenon as "focus or Newton's rings".) These may be almost as fine as the dot pitch on the CRT or 1 or 2 cm or larger and changing across the screen. If they are more or less fixed on the screen and stable, then they are not likely to be outside interference or internal power supply problems. (However, if the patterns are locked to the image, then there could be a problem with the video board.)
One cause of these lines is moire (interference patterns) between the raster and the dot structure of the CRT. Ironically, the better the focus on the tube, the worse this is likely to be. Trinitrons, which do not have a vertical dot structure should be immune to interference of this sort from the raster lines (but not from the horizontal pixel structure).
You can test for moire by slowly adjusting the vertical size. If it is moire, you should see the pattern change in location and spatial frequency as slight changes are made to size. Changes to vertical position will move the patterns without altering their structure - but they will not remain locked to the moving image.
If they are due to the raster line structure - your focus is too good - the patterns will remain essentially fixed in position on the face of the CRT for horizontal size and position adjustments - the patterns will remain fixed under the changing image.
How to eliminate it? If moire is your problem, then there may be no easy answer. For a given resolution and size, it will either be a problem or not. You can try changing size and resolution - moire is a function of geometry. Ironically, I have a monitor which is nicer in this respect at 1024x768 interlaced than at 800x600 non-interlaced.
Some monitors have a 'Moire Reduction Mode' switch, control, or mode. This may or may not be of help. One way to do this is - you guessed it - reduce the sharpness of the beam spot and make the picture fuzzier! You might find the cure worse than the disease.
Another cause of similar problems is bad video cable termination creating reflections and ghosting which under certain conditions can be so severe as to mimic Moire effects. This is unlikely to occur in all colors with a VGA display since the termination is internal to the monitor and individual resistors are used for each color (RGB).
I think it is ironic that some people will end up returning otherwise superb monitors because of moire - when in many cases this is an indication of most excellent focus - something many people strive for! You can always get rid of it - the converse is not necessarily true!, .




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