Why is ULMB making Fortnite so smooth?!

[GFresha]

Not sure wuts going on I was on 240 FPS cap, no sync I decided to run ULMB mode with no other sync and that same 240 FPS game and now my game is smoother? Was motion blur making my game feel laggy to my eyes or wots goin on?

I know this is silly but all sudden I'm aiming and building better I think it might be placebo effect honestly but Fortnite is a 3rd person game so I don't know... I feel like this mode is perfect for 3rd person games and not so much 1st person FPS like OW,CS,Apex etc...

[Chief Blur Buster]

Not sure wuts going on I was on 240 FPS cap, no sync I decided to run ULMB mode with no other sync and that same 240 FPS game and now my game is smoother? Was motion blur making my game feel laggy to my eyes or wots goin on?

I know this is silly but all sudden I'm aiming and building better I think it might be placebo effect honestly but Fortnite is a 3rd person game so I don't know... I feel like this mode is perfect for 3rd person games and not so much 1st person FPS like OW,CS,Apex etc...

ULMB can benefit 3rd person more than 1st person, because with 3rd person, you've got lots of panning as you turn -- and that creates a lot of forced-eye-tracking situations where motion blur reduction helps greatly.

Framerate-refreshrate synchronized ULMB is among the best motion you can get in gaming. Are you using VSYNC ON or VSYNC OFF, or just a framerate cap to match framerates approximately to refresh rate?

Strobing adds a very slight latency but the improved reaction time of lack of motion blur, can sometimes compensate. There are situations where motion blur slows down your reaction time, and the elimination of motion blur fixes that!

It depends on your gaming tactics. But there are situations where your improved reaction time (reduced reaction time lag) more than outweighs the strobe lag (technological lag). On average, strobing at 144Hz adds an average of 1/2 of 1/144sec (~3.5ms extra lag) and strobing at 240Hz adds an average of 1/2 of 1/240 (~2ms extra lag). Depending on strobing settings, this can be less or more. If your reaction time improves by 10-20ms because of lack of motion blur, then it's a win. Not all games benefit but Fortnite is sometimes one of those surprising games (in certain situations).

See HOWTO: Using ULMB Beautifully or Competitively.

[GFresha]

I didn't think about the fact that sure, input delay is slightly increased, but the fact that motion clarity is improved and therefore reaction time is improved but also the game even looks so much better to my eyes compared to ULMB off that my performance is going up.

Does input delay increase even if vsync is off? Where does the delay come from? I have to go down to 120 hz to enable this ULMB mode so I'm guessing this 24 hz difference between 144 and 120 is where the input delay comes from for ULMB? Or does the mode it self add extra input delay on top of the fact that input delay is already increased by going down from 144>120 hz?

Only been using it for a day or so so def gona keep testing and see if I regress back to how I usually play or if its really making big changes for me. But yeah man its fitting Fortnite perfectly.

[Chief Blur Buster]

VSYNC OFF will not completely eliminate input lag. And you might actually get preferable latency mechanics with a low-latency variant of VSYNC ON (i.e. RTSS Scanline Sync) -- though it depends.

It comes from the fact that not all pixels on the LCD panel refreshes simultaneously, see High Speed Videos of LCD Refreshing.

For a motion-blur strobe backlight, a backlight is turned off while the LCD refreshes, and the backlight is flashed when the panel is refreshed. See High Speed Video of LightBoost/ULMB.

The lag comes from the need to refresh the LCD panel in the dark between strobe backlight flashes (once per refresh cycle). Average lag penalty is the halfpoint of the refresh cycle, top edge most lagged, bottom edge of least lagged.

The latency gradient also will be different for VSYNC ON versus VSYNC OFF, strobed versus non-strobed. So you will have different lagfeel for the four different combinations. The most consistent (least volatile) lag, but highest average lag, actually comes from VSYNC ON + strobed, since VSYNC ON is a global sync tech, and strobed is a global flash. You get high lag, but you get glassfloor lag (and zero lag gradient top edge-thru-bottom edge) of framerate=Hz.