I have an Ask Impact 24 panel (640x480, 16.7m cols, 30ms response) on a 4000 lumens OHP (3M 1750) fed by the VGA output of a progressive scan DVD player (Arianet PDVD2255).
The results of this combination are basically excellent (good colour, contrast etc) with one exception. During movement on screen (it doesn't have to be that fast) the panel shows very obvious and distracting diagonal interference lines. With a static or near static picture the image is *very* good with little or no noise.
I can only put these diagonal lines down to one of two things:
1) Aliasing between the VGA resolution and the DVD resolution
2) Slow response time of panel
However, the first is likely to be down to the DVD player and I haven't seen it on other panels I have tried (Spectra C and Ovation 820 - both 640x480 resolution too). The second seems unlikely as 30ms is a pretty respectable response time.
I got the chance the other day to try out another Ask Impact 24 and it exhibited the same effect.
S-Video and composite video into the panel do not showthe same problem (but the general video quality is poor compared to the direct VGA out from the DVD player).
Anybody got any other ideas or experience of similar effects?
My feeling is to try a higher resolution panel to see if it helps (but this will only help if the problem IS aliasing).
The results of this combination are basically excellent (good colour, contrast etc) with one exception. During movement on screen (it doesn't have to be that fast) the panel shows very obvious and distracting diagonal interference lines. With a static or near static picture the image is *very* good with little or no noise.
I can only put these diagonal lines down to one of two things:
1) Aliasing between the VGA resolution and the DVD resolution
2) Slow response time of panel
However, the first is likely to be down to the DVD player and I haven't seen it on other panels I have tried (Spectra C and Ovation 820 - both 640x480 resolution too). The second seems unlikely as 30ms is a pretty respectable response time.
I got the chance the other day to try out another Ask Impact 24 and it exhibited the same effect.
S-Video and composite video into the panel do not showthe same problem (but the general video quality is poor compared to the direct VGA out from the DVD player).
Anybody got any other ideas or experience of similar effects?
My feeling is to try a higher resolution panel to see if it helps (but this will only help if the problem IS aliasing).
would you describe these interference lines more like "tears in the image"... as if every so many rows of pixels have been offset a little bit... causing the image to looks "spikey" in certain areas where there is movement... especially noticeable during high contrast scenes? if so you might be having the same problem as me... through the process of elimination i was able to determine that my xbox dvd player (interlaced) was the source of those artifacts. it's puzzling that you are getting this with a progressive scan dvd player. the only thing i can think of is that your dvd player works differently on vga out. you could try using another vga out player (although i think there is only 1 player out there with vga out) or hook the panel up to your pc and see if the same problem occurs. i doubt it's your panel... slow response lcd's would produce a "ghost" image during fast movement, not the artifacts that you are describing.
I also suffer from this problem. I think it's a ground loop issue and we are only seeing it with movement because that is when our eyes are moving in the right direction. For me, the amount/speed of the interference depends on the refresh rate used from my computer. Are your DVD player and panel plugged into the same wall outlet? If not, try it that way and see if it fixes the problem. I wouldn't mind getting rid of this myself..
Axeman, that's a very good point. Although my DVD and panel are in the same wall socket they could still have different ground paths.
I know you can get composite video ground loop isolators. Anyone know if you can get VGA ones?
I know you can get composite video ground loop isolators. Anyone know if you can get VGA ones?
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