While I was away at GTC, Allyn did some more work looking into and exploring the ghosting we saw on the FreeSync monitors. In the animation above you can see three different displays at work, all using the AMD FreeSync demo of a windmill rotating and also panning on the screen. On the left is the G-Sync enabled ASUS PG278Q ROG Swift at 144 Hz refresh rate; in the middle is the BenQ XL2730Z 144 Hz monitor and on the right is the LG 34UM67 at 75 Hz. The animation frame rate was set to 45 FPS for both the ASUS and BenQ displays but the LG had to be set at 55 FPS due to limitations of the demo software.
The ROG Swift animates at 45 FPS without any noticeable ghosting at all. The BenQ actually has a very prominent frame ghost though the image still remains sharp and in focus. The LG 34UM67 shows multiple ghost frames and causes the blade to appear smudgy and muddled a bit.
The question now is: why is this happening and does it have anything to do with G-Sync or FreeSync? NVIDIA has stated on a few occasions that there is more that goes into a VRR monitor than simply integrated vBlank extensions and have pointed to instances like this as an example as to why. Modern monitors are often tuned to a specific refresh rate – 144 Hz, 120 Hz, 60 Hz, etc. – and the power delivery to pixels is built to reduce ghosting and image defects. But in a situation where the refresh rate can literally be ANY rate, as we get with VRR displays, the LCD will very often be in these non-tuned refresh rates. NVIDIA claims its G-Sync module is tuned for each display to prevent ghosting by change the amount of voltage going to pixels at different refresh rates, allowing pixels to untwist and retwist at different rates.
It’s impossible now to know if that is the cause for the difference seen above. But with the ROG Swift and BenQ XL2730Z sharing the same 144 Hz TN panel specifications, there is obviously something different about the integration. It could be panel technology, it could be VRR technology or it could be settings in the monitor itself. We will be diving more into the issue as we spend more time with different FreeSync models.
For its part, AMD says that ghosting is an issue it is hoping to lessen on FreeSync monitors by helping partners pick the right components (Tcon, scalars, etc.) and to drive a “fast evolution” in this area.
FreeSync is doing the right things and is headed in the right direction, but it can’t claim to offer the same experience as G-Sync. Yet.
