Gaming: response time and input lag
This is what it is all about when you are looking for a gaming monitor: the speed. We tested both monitors extensively in order to measure this. Because these tests were unchanged there is plenty of comparison material as well. If you skipped directly to thig page: the blue bars are the 1920x1080-monitors, the red ones are 2560x1440-models, the XL2735 is purple and the XL2540 is green.
If you want to take a look at all the graphs: we show, in a manner of experiment, both the rise and fall times separately, as well as the combined values. We also show the maximum and optimal overdrive results. The optimal overdrive values are combined rise / fall response times of 16 ms or lower with an overshoot that is as low as possible. In other words: a response time of 4 ms and an overshoot of 60% is in our opinion worse than a response time of 15 ms combined with an overshoot of 5%. After all, overshoot and undershoot result in annoying artefacts around moving parts of the image, mainly with contrast-rich gradients you can see thick white or black edges. In our opinion, these are worse than light ghosting.
Without overdrive active the Benq monitors are clearly fast, but are just shy of being in the top-10. At maximum overdrive this is not the case, but in all honesty: the measured speeds are more than enough in order to show 144 frames per second. The XL2540 measures 4.2 ms with max overdrive for a single transition. If we divide 1000 by 240, we end up at 4.16 ms – which is as long as it can take in order to reach the refresh rate. This means it is possible. With grey-grey transitions we measure 4.9 ms: slightly too long. In theory ghosting is there, in practice it is definitely questionable if you will notice it. In any case, we do not. At maximum overdrive the XL2540 does show severe overshoot, 31%. This means you will see some artefacts. In our opinion you will be better off turning down the overdrive one stance (to ‘high’) – this means you end up at 4.8 ms for a single (rise) transition, and minimum overshoot.
Of course you will question why all the other monitors with lower response times are not the better option. This is very simple: they simply show every image for a longer time. It shows up faster, but also stays longer – the XL2540 already shows a new image (provided that it is supplied by the graphics card). In short: response times are only part of the story.
Taking a look at the XL2735, we should first say that we were only able to measure these times in order to deactivate the DyAc-function in the system menu, after special instructions from Benq. Normally this is not possible. Therefore, Benq says that these results are not representative per se – but we want to compare it to other monitors and this way you at least have a basic idea of the speed. The actual speed is of course better, because motion blur is not as present than with other competing models that do not have scanning backlight. We see very respectable response times anyway, that are even higher with the optimal setting than with the XL2540. Once again with the caveat that the bigger monitor will never be able to produce more than 144 frames per second, whereas the XL2540 can.
Response times standard
Response times maximum
Response times optimal
Remarkably enough we noticed some (very small) input lag with the XL2540 during our input lag measurements – but it is gone as soon as the entire image is shown. The same goes for the XL2735 – there is a disadvantage of about 4 ms compared with the fastest competitors, but when the entire image is shown it goes away. With that monitor the reason surely has something to do with the changing of the incoming signal to the frequency of the panel. With the XL2540 we do not know for certain what is going on. What we do know for certain is that while the difference is certainly measureable, it is not noticeable. In comparison with a crt the difference is too small to capture.