This option is available by default at refresh rates of 120, 144 and 240Hz only. We did find that we could create custom resolutions with a refresh rate of 100, 85 and 75Hz and that the VRB mode would also run at those refresh rates if we wanted. It did not work at 60Hz though and was unavailable. As you got in to the lower refresh rates like 85Hz and 75Hz the flickering became more visible, so it's probably not recommended to use it at such low settings if you can help it.

We measured the on/off strobing using our oscilloscope and confirmed that the strobing is in sync with the refresh rate. So at 240Hz for instance (shown above) the backlight is turned off/on every 4.17ms (240 times per second). There is a 2ms 'on' period followed by a 2.17ms 'off' period in this normal mode. As you reduce the refresh rate the strobing remains in sync with it well. The 'on' period actually remains the same length at 2ms, and it is just the 'off' period that is extended. So for instance at 120Hz the on period is 2ms and the off period is 6.33ms. This means that the overall image ends up being darker as you lower the refresh rate, which is contrary to most other strobing backlight options we've seen in the past. The brightest appearance is therefore at 240Hz on this screen.