We've mentioned the new Ultra HD G-Sync HDR ACER and ASUS monitors a couple of times already. Over the weekend some reported the ACER one got in the news due to a loud ventilator, today more news reaches the web, in high-refresh-rate modes, the displays fall back to color compression.

A few early adopters of these HDR, local dimming monster monitors noticed and reported on Reddit that when using a high refresh rate, the image quality dropped significantly. The story now is that the ASUS and Acer screens make use of color compression at 120 and 144 Hz, not because the panel couldn't handle it, but the main limitation is signal bandwidth over DisplayPort 1.4. This also means you pretty much need to run your Windows desktop at 60 Hz for a bit of a quality readable view. 

DisplayPort 1.4 has too little bandwidth available to drive 4k, 144 Hz without compression. To bypass that, the screen monitor signal reverts to 4:2:2 chroma subsampling. basically your brightness information will remain intact, however, the color information will be based on half the resolution, 1920 x 2160 pixels. All is good up to 98 Hz, after that, it's 4:2:2 chroma subsampling  ... on your 2500 Euro / 2000 USD Screen. Lovely.  There's no real solution for this, other than new display connectors and graphics cards that do support such high bandwidth connections - HDMI 2.1. 

chroma subsampling. (Picture: Wikimedia )

ASUS and Acer UHD G-Sync HDR Monitors Forced to Use Color Compression at 120/144 Hz