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Conventional wisdom suggests that there seems to be no discernable difference between PC mode (called "D. PC RGB" in the user menu) and video mode (called "D. Video RGB") when using a source connected to the Sharp 12K via DVI. This is basically because the expected use for this setting is to properly establish black and white levels for digital signals, which are different in the PC and video realms. The Sharp 12K seems to ignore this difference, always using the PC levels for black (0) and white (255) no matter what signal type you specify in the user menu. This is fine because the addition of brightness and contrast controls when DVI is in use allows the user to compensate for these differing black and white levels.


In my testing, I've discovered that when sending the 12K a 720p source via DVI, there most definitely is a difference between the D. PC RGB setting and the D. Video RGB setting--but it's not in the black level. The issue is sharpness, or more accurately edge enhancement.


Using both an LG LST-3510A DVD player that upscales to 720p via DVI and my HTPC equipped with a Radeon 7500 set to [email protected], I've found that when using "dot-by-dot" mode on the 12K (1:1 pixel mapping being the more familiar term), the 12K adds a noticeable level of edge enhancement when set to D. Video RGB. However, when using D. PC RGB, the images from both the DVD player and my HTPC are clean and clear, with no artificial sharpening. This sharpening is most evident on the Windows desktop, where black text exhibits a very obvious glow around the edges.


Lowering the Sharpness setting to about -8 appears to get rid of the unwanted edge enhancement, but the image still seems a tad softer than when using PC mode.


I didn't try a 720p VGA signal, but it wouldn't surprise me if the same artifact shows up. Be sure to experiment on your own to see what works best with your setup, but I would suggest that those of you sending 720p signals through DVI to your Sharp 12K switch the input mode to D. PC RGB and avoid some unnecessary processing, regardless of whether you're using a PC or DVI DVD player.
 

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Thanks Jay. I had noticed that the sharpness control went away when setting the input to PC and had also noticed the edge enhancement, but hadn't noticed as many things as you did. I had set the sharpness to -10 while using video mode, I believe. I didn't really compare the image at that point to using PC mode while using the Momitsu V880, though. Maybe I'll try that at some point. I wonder if there is any difference in the amount of mosquito noise that would be visible or anything like that.


--Darin
 

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Thanks Jay for the advice. I have noticed the same thing when using my SAT 520 with the DVI output. The black level was much higher and the picture softer. The component input gave a much better picture. The Zenith box does not have any adjustments for the black level. I haven't played with it yet, to see if I could get the same (or hopefully better) PQ with the DVI. that's the whole reason for using it! I think I've been using the D. Video mode, though. Will have to try it with the PC setting.


Jeff
 
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