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BenQ XL2730Z – Input Lag with Freesync

 

BenQ XL2730Z – input lag with Freesync – engineering information from BenQ

 

Whilst I hate to use the word ‘exclusive’, the information contained within this post, however, has been pretty hard to track down (believe me!).

At RageQuitters, we are big fans of TFTCentral.co.uk‘s monitor reviews which provide some of the most in-depth monitor reviews available on the internet.

During their review of the outstanding BenQ XL2730Z 144hz TN 1ms 27″ Freesync gaming monitor, TFTCentral noted the difference in the lag section between a 60hz vs 144hz ‘fixed’ signal – a fairly poor 16.22ms for 60hz vs an excellent 5.25ms for 144hz (4ms with ‘instant mode’ enabled).

TFTCentral also noted that the 16.22ms for 60hz does not improve when ‘instant mode’ is enabled in monitor’s OSD settings (for reference, instant mode is designed to bypass some of the monitor’s internal electronics to reduce the input lag as much as possible).

It is safe to assume that BenQ have clearly focused their engineering efforts in ensuring that the primary input and refresh rate (DisplayPort @ 144hz – for which the target audience the monitor is intended for) has the lowest input lag possible.

Stopwatch

The lag results are also disappointing for those intending to use the monitor with a fixed 60hz signal (e.g. a games console over HDMI) and I would have my reservations recommending the monitor for this purpose.

However, it does raise the question “what about a Freesync signal which starts at 144hz and reduces down to 60hz during gameplay when your framerate drops to 60fps?” – a situation which will not be uncommon (especially in modern titles) considering the monitor’s fairly high 2560×1440 (1440p) resolution unless you are packing a serious Crossfire setup.

I’ve asked this question in the past before and the answer has always been “this is very difficult to measure accurately” with a tool such as SMTT2 (which is designed to measure monitor lag at fixed refresh rates).

Just as a point of clarification, if you have not experienced or read up on AMD’s Freesync or NVIDIA’s G-Sync technologies, adaptive synchronisation works by matching the monitor’s refresh rate to the current framerate that your graphics card is pumping out. 

For example, if your graphics card is outputting 72 frames-per-second, your Freesync monitor will match this and alter the refresh rate of the monitor to 72hz.  As your framerate fluctuates, the refresh rate of the monitor (within a predetermined range – 40-144hz in the case of the BenQ XL2730Z) and continuously track and match its refresh rate to stay in sync.

Unlike a fixed vertical sync (V-Sync – which adds significant input lag) or running with V-Sync ‘off’ (which introduces graphical ‘tearing’), Freesync (and G-Sync) provide the ‘best of both worlds’ providing a smooth, tear-free gaming experience without any additional input lag.

BenQ_XL2730Z

For those of you out there who are as obsessed with input lag (aka display lag) as I am, I’m sure you will greatly appreciate the clarification I have received for BenQ’s customer service / engineering team on this matter which was as follows:


Subject: Re: BenQ XL2730Z – display input lag 60hz ‘fixed’ vs. 60hz ‘freesync’
Date: Fri, 22 Apr 2016 15:35:25 +0200
To: terminatoruk@ragequitters.co.uk
From: cets@benq.eu

Dear TerminatorUK,

Thank you for contacting BenQ

Here the information regarding input lag related to FreeSync. The below is the only information we can provide. In case you need to know more details about FreeSync Technology and why the FPS/ refresh rates drop and raise, please contact AMD services.

When using a:

1.  Freesync signal: The monitor directly displays the content on the panel which the AMD Freesync graphic card outputs to the monitor. There is no signal processing needed in the monitor itself.
(Saving lag time, because this technology runs without memory flash or RAM processing time.)

Why monitor fps / refresh rate drop and raise? Because AMD Freesync adopts DRR (Dynamic Refresh Rate) technology mechanism. Still the input lag remains the same.

2.  General signal: Input signal needs to travel through the monitor’s internal memory flash or RAM for processing then gets displayed on panel, so it may take some time (higher lag on the signal processing)

Regards

BenQ Europe
http://benq.co.uk

Vat No. 713005001 – Registered in England 3462488
Registered address: 7/10 Chandos Street, Cavendish Square, London, W1G 9DQ

Visit the BenQ Online Store
http://shop.benq.eu/store/benqeu/en_GB/home


The key points to note here are:

  • Freesync runs directly from the output of the graphics card at all refreshes – it does not spend time in the monitor’s internal flash / RAM – input lag remains the same
  • ‘Fixed’ signals travel through the monitor’s internal flash / RAM and therefore may take some time.  This has obviously been optimised for 144hz but not in the case of a ‘fixed’ 60hz signal

 

So there we go folks, confirmation from the horse’s mouth (so to speak) that your input lag with this monitor will remains constant whilst using Freesync at all refresh rates; any RageQuitting due to ‘lag’ with this purely all in your head (or lack of skill)!

Happy gaming! 🙂

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