Ghosting of moving objects in games

[8bit]

Long shot this but here goes.

I'm finding that in certain games (HL2 stuff, Portal 2 specifically) I can see ghosting, like a black shadow that follows light-coloured objects as they move quickly across the screen.

I recently upgraded my graphics to a HD 7950. I know the usual explanation for ghosting tends to be the screen rather than the graphics card but while I can't be 100% sure, I don't remember seeing this on my old GeForce 8800GTX (but it was about a year since I last used it as it died on me). The screen is the same as before, an LG 32" 1080p TV.

I guess the answer is likely to be "get a better screen" but as I don't remember seeing ghosting on my old graphics card I thought it might be worth a post to see if there's some setting or soimething that's known to cause a shadow/ghost effect like this with this card?

Thanks in advance.

[shaithis]

You could try changing the DVI/HDMI/VGA cable in case there is a weird impedance issue....but I am guessing a difference in RAMDACs or display quality is making them more pronounced then they were before and it is just the monitor.

[scaryjim]

... I know the usual explanation for ghosting tends to be the screen rather than the graphics card but while I can't be 100% sure, I don't remember seeing this on my old GeForce 8800GTX ...

Could just be that the 8800GTX wasn't pushing out a high enough framerate for the ghosting to be noticeable? Jumping from that to a 7950 is quite an upgrade...

I can't imagine a 1080p TV has a particularly good grey-to-grey response - LG don't even list it on their website, and for TV purposes it's not really a priority. If the 8800GTX was pushing high 20s on a regular basis it'd probably feel fairly smooth, but it'd still be refreshing slowly enough that you wouldn't notice the ghosting. The 7950 is probably pushing double that, so the ghosting time is proportionately much longer. I noticed this on my old TV - watching films from DVD/TV there was no obvious ghosting, but the PC caused noticable ghosting.

[kalniel]

RTC overshoot by the TV. There's an option in the catalyst control centre to correct for it. (LCD overdrive control?)

[8bit]

RTC overshoot? I'd seen that LCD overdrive in the settings but hadn't looked at it yet. If I switch it on it kills Aero and I see the preview. I can see slight shadows following the lines across the preview, if I turn the effect up they get worse though. I'll have a go at Portal 2 with this setting on and see if it makes any difference, thanks.

@shaithis, I did switch from a DVI -> HDMI cable to a regular HDMI cable when I installed the card, if no joy with the above I'll try the original cable and see if that helps, thanks.

@scaryjim, thanks for that, can see the logic there, maybe that it's just that. I'll try the other suggestions and see what's what.

[kalniel]

RTC overshoot? I'd seen that LCD overdrive in the settings but hadn't looked at it yet. If I switch it on it kills Aero and I see the preview. I can see slight shadows following the lines across the preview, if I turn the effect up they get worse though. I'll have a go at Portal 2 with this setting on and see if it makes any difference, thanks.

It might just be killing aero for the preview, it shouldn't affect it in general (I used to run with it on my last monitor).

Sometimes turning it on and then keeping the slider all the way to the left is helpful, sometimes it's hardwired on the monitor and you can only make it worse.

RTC is a method of decreasing pixel changing time (response time correction) by essentially overclocking (overvolting) the pixel hardware. However if this isn't done subtly then it can overshoot the value, so when you're changing from black to grey, RTC can overshoot and you get a brief moment of white before it settles on grey - this looks like a ghost following the object. Ditto white to grey overshooting to black.

[technodean]

In the tv settings , have you turned off the auto settings, i.e noise filter, motion blur etc. Plus what htz is the tv?

[8bit]

It might just be killing aero for the preview, it shouldn't affect it in general (I used to run with it on my last monitor).

Sometimes turning it on and then keeping the slider all the way to the left is helpful, sometimes it's hardwired on the monitor and you can only make it worse.

RTC is a method of decreasing pixel changing time (response time correction) by essentially overclocking (overvolting) the pixel hardware. However if this isn't done subtly then it can overshoot the value, so when you're changing from black to grey, RTC can overshoot and you get a brief moment of white before it settles on grey - this looks like a ghost following the object. Ditto white to grey overshooting to black.

Actually yeah, it restores Aero when I close the Catalyst settings thing.

I tried it all the way left and all the way right, didn't seem to make much odds in-game (I was testing it with Portal 2, the first level where the cube is bouncing on the aerial faith plates - the cube is near-white and the background in the scene is dark grey so I get a black trailer behind the cube). Having the slider all the way left did seem to help the ghosting in the preview a little, all the way right made it much worse.

Thanks for the info on RTC

In the tv settings , have you turned off the auto settings, i.e noise filter, motion blur etc. Plus what htz is the tv?

Thanks for the post. The TV has a setting where you label each input with a generic device type. When I first got it I discovered that once I'd set it the HDMI input I used to "PC" it seemed to switch off image scaling, processing etc. and just do a 1:1 pixel display, like a monitor does.

I just had a look in the settings, it looks like most of the settings you describe are forced off, think that's cos it's set to PC for this input. I tried setting the input to "GAME" and it messed up the scaling so I had to adjust the scaling in the Catalyst control panel but the image quality was poor. It's running at 60Hz.

I have Vsync forced on in Catalyst, I'll try disabling that and see if it makes any odds. Will have a go with the DVI-HDMI cable I was previously using too.

[DLUK]

The black ghost can also be an effect of Ambient Occlusion in some games. So if you see it only in some games not others it's the DX10-11 doing the ambient stuff. BF3 is one of the games I have seen it in.