U2518D, PS4 Slim, GTX 960, tearing, stuttering
first of all, I need to stress that it's clear, that this seems to be a common issue with U2518D, because I can find on the internet numbers of people, who have exactly same problem as I am (except they are NOT using the PS4), for example. So the problem is basically "tearing" in every game or 3D application despite that the Vsync is ON and FPS well over 60. I call it "tearing", because it looks very much like tearing in games with disabled Vsync. But it doesn't look entirely like that, because normal tearing is usually only one horizontal line when the image is shifted, but in case of the U2518D, this line goes all the way from top to bottom, like entire image is refreshed. Because of that, it is much more distracting that usual tearing with disabled Vsync.
I also found out, that it is related to the resolution like this:
2560x1440 - GTX 960, DisplayPort -> U2518D mDP port
In this resolution, every +/- 26 seconds, the monitor display rather then tearing more like stuttering, so every 26 seconds there is short stutter and maybe minor tearing. This is quite distracting, it is not as much strong but it is too often, basically it is there all the time.
1920x1080 - GTX 960, DisplayPort -> U2518D mDP port
In this resolution, every +/- 36 seconds, there is the tearing mentioned above (and also in the post by Thomas_nx5). This is extremely distracting, not only it happens way too frequent, but it looks really horrible as well.
1080p - PS4 HDMI -> U2518D HDMI
Same problem like in 1920x1080 on PC with DP.
720p/1080i - PS4 HDMI -> U2518D HDMI
Strangely enough, in 720p and even in 1080i, there is absolutely no problem with tearing. The movement is perfectly smooth, no tearing, no stuttering.
Other resolutions - GTX 960, DisplayPort -> U2518D mDP port
2560x1440 - stuttering
2048x1080 - OK, no tearing/stuttering
1920x1080 - tearing
1600x1200 - OK, no tearing/stuttering
1280x1024 - OK, no tearing/stuttering
1280x720 - OK, no tearing/stuttering
1024x768 - OK, no tearing/stuttering
So as it looks, the problem with smoothness is only in native 1440p and 1080p resolution. But of course, that is huge problem, because obviously, we want to use this monitor in a native resolution. All test was done also on my second monitor, HP ZR24w, where is absolutely no problem with smoothness of the movement. So it's clear, that the problem is in U2518D, not in PC, PS4 or anywhere else. As a test for PC, I tested it in many games and also found this handy utility by Nvidia which nicely show the problem as well and it is very fast to setup. Just click on 60 FPS, turn on Vsync and turn on orbit camera with maximum speed.
So please, as this (in my opinion) is really looking like systematic problem for U2518D. Can someone from the technical department look at this and diagnose properly IF this is indeed a problem? Why is this happening and what can be done with it? If it is a problem for all U2518D, or there are only couple of defective examples? If it is a problem with firmware, which may be updated? I found out that Dell U3415W monitor received firmware update that should resolve a problem with flickering. So my question is, what need to be done to do this? What do we customers have to do, so Dell technical department look at this and maybe fix the firmware or at least say that this is just a "feature" of the U2518D and it never be smooth in 1440p/1080p, so we can return this monitor and buy something else? The fact is, that with exception of this problem, I am very satisfied with this monitor. I like the image quality, design, it has perfect size and resolution. It has very good response time and minimal input lag. Also my monitor has no dead pixel or any major problem with uniformity of luminance. So I really don't like the idea to return it and replace with another U2518D, which may be worse and probably not solve this problem at all.
EVGA GTX 960 SC 4GB - DisplayPort
Windows 7 64-bit
PS4 Slim 1TB - HDMI
I also tried to change version of DP and HDMI in monitor setup, but none of that helped.