That is caused only when the video outputs are not perfectly synchronized. This will invalidate an input lag comparison test. One needs to use identical resolution and refresh rate, for synchronized output. A verification step should be done to make sure the outputs are in sync before trusting the lag test. Also, surround mode uses synchronized output too.flood wrote:for uberniner's system yea, but for my system (gtx 750ti, win7 clone mode) the tearlines are always different.
This will isolate the lag to the monitors (and any cable differences, such as the difference of input lag of HDMI versus DVI versus DisplayPort versus VGA. That adds a 1-2ms lag error margin, now bigger than the signal lag of a modern 120Hz+ monitors).
SMTT style tests are going to always show near zero lag with these modern monitors, greatly affected by the error of the differences between signals, the GtG, the framerate granularity, and the camera sensor rolling scan. You may get readings of 1ms or 2ms lag like TFTCentral got, then it gets overwhelmed by the various lag error margins.
This is why I am now a huge advocate of full-chain testing. This is why I tested GSYNC from button-to-pixels, to capture GSYNC influences on both the monitor side and the computer side of things, including whatever driver techniques is being done to reduce lag for a specific custom display tech (ala GSYNC).