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TOPIC
I am using a Power Macintosh 8500 series computer to output video to a video display. Regardless whether I use NTSC or S-video, when an image with a very large area of black is displayed on the video monitor, the image is significantly distorted. The problem is most evident when displaying an all-black window with white borders. The display appears pincushioned, especially on the right hand side and is most severe where there is the most black displayed.
DISCUSSION
The distortion is most likely caused by the performance level of the display being used. If the black portion is moved, the distorted area will probably move with it. This is common for many consumer and middle-performance displays. High-performance displays would have little or no distortion of this type.It's likely that the video signal from the computer is fine. To verify this, you can record the signal that causes the distortion on video tape. Then, play the video tape and record the signal using the video record feature in the computer. You could then view the captured video on the computer display toÊconfirm that the distortion is not in the tape recorded signal.
If you can't capture the taped video signal using the computer, you should check the signal using a high performance display.
To reduce or eliminate this distortion, you can use shades of gray instead of large black and white areas. Or, use colors instead of black like fully saturated blue, red, or green in large areas.
You should also note that although this distortion would likely appear on home televisions as well, most people will likely not notice it because consumer television have overscan, which prevents you from seeing the edges of the video signal.
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