Minimum refresh rate for ULMB?

SmSumodude20 · July 11, 2015

I was trying to find some information on NVIDIA's Ultra Low Motion Blur setting on most G-sync monitors. I've read that at a low refresh rate like 60hz strobed lighting gives off a noticeable flickering, but this is when using Lightboost. I haven't found a G-sync monitors that lets you use ULMB under 85hz setting, but I haven't seen anything saying it's impossible to go lower than that either. I was wondering if anyone knew more about this, and could explain if it's possible to go lower than 85hz. I was mainly just wondering because the Acer XR341CKA and ASUS PG34q were recently confirmed to have ULMB meaning it's more likely to have 100hz refresh rate now, or 85hz minimum.

July 11, 2015

there are a few 85hz implementations out there, but 100hz really SHOULD be the minimum....

you could make it for 30hz if you really wanted(there are some firmware hacks that can do this for one specific benq monitor) - but youre eyes would melt out of your fucking skull

Falkentyne · July 11, 2015

There are no firmware hacks (a service menu setting is not a hack), and he's referring to the Benq Z series before the XL2730Z (this includes the XL2430T which should have been named XL2430Z).

There is a setting In the service menu (the XL2730Z is missing this setting) that will allow it to single strobe (synced with the refresh rate) lower than 100hz. Turning this option on will enable single strobe down to 60hz refresh rate. This will cause backlight flicker just like you would get on a 60 hz CRT.

There is no 30 hz strobing. 30 hz refresh rate isn't even 30hz, it's basically 60hz interlaced. The lowest strobe data in the monitor for single strobe is for 60hz. Turning single strobe to off will cause it to double strobe (strobe every other refresh or strobe twice per refresh, I forgot which, but the brightness is doubled and there is a distinct double image during movement), so 60hz will strobe at 120hz pulses (this looks ugly but doesn't flicker and still looks better than no strobing at 60hz) and 50hz refresh rate will strobe at 100hz pulses.

There is no single strobe data for 50hz at all (60hz is the lowest). Setting 50 hz and turning on single strobe will fail to strobe at all, the backlight current will be increased beyond specifications, beyond what 100 brightness even would give non-strobed, and will make the monitor either hard reset or shut off from overcurrent protection (Benq blur reduction and its predecessor, Lightboost, both increase current to the backlight to compensate for the loss of luminance during strobing, ULMB does not do this, which is why many people find low pulse width ULMB too dim).

The Benq XL2730Z double strobes at 60hz (120hz pulses) and strobes incorrectly, using 120hz pulses at 100hz, causing very bad stutter, as it is missing proper 100hz single strobe (it can only strobe at 120 and 144 hz correctly). This is a bug that has not been fixed in V002 and there is no more information about this, although Chief Blur Buster (from the blur busters' website) is aware of this bug.