To learn how we measure screen uniformity, please click here.
By using TN panels, Dell and its competitors are pushing 4K resolution into an affordable price range. Poor off-axis image quality is the most significant trade-off. When viewed head-on, TN technology looks fine. But at 45-degree vertical and horizontal positions, the picture degrades quite a bit. To the sides, an obvious red cast comes into play, while from above or below, detail is almost completely wiped out.
Screen Uniformity: Luminance

Our sample returned some of the best results we’ve seen in the black field uniformity test. There is no visible light whatsoever. Instead, you get a smooth continuous tone across the screen. We’ve reviewed a few monitors with uniformity compensation look-up tables that couldn’t do better.
Here’s the white field measurement:

Although this is a good result, it’s rare that any display's uniformity is lower in the white field test. It’s only a nit-pick, however. We still couldn’t see any hotspots on our sample.
Screen Uniformity: Color

Color uniformity is quite low as well. It was a weak point of TN-based monitors in the past, though the newest panels post more impressive results. Aside from the viewing angle issue, there’s no reason not to consider TN if it meets your other needs.
Pixel Response And Input Lag
Please click here to read up on our pixel response and input lag testing procedures.

We tested the P2815Q at 1920x1080 in order to match the other monitors’ 60Hz refresh rates. At 30Hz, you can expect a result closer to 25 milliseconds. Either way, it slightly bests Asus' effort, which uses the same Chi Mei panel.
The lag results were something of a surprise.

This measurement is more what we’d expect from an HDTV, not a computer monitor. Remember, we’re testing at 60Hz here. Using the P2815Q in its 3840x2160 at 30Hz mode produces so much lag we can see it by just moving the mouse cursor in Windows. Playing Watch Dogs at native resolution is pretty much impossible with a GeForce GTX 780 graphics board. Based solely on the input lag result, we cannot recommend the P2815Q for any kind of motion-oriented gaming.
- Dell P2815Q 28-Inch Ultra HD Monitor Review
- Packaging, Physical Layout, And Accessories
- OSD Setup And Calibration Of The Dell P2815Q
- Results: Brightness And Contrast
- Results: Grayscale Tracking And Gamma Response
- Results: Color Gamut And Performance
- Results: Viewing Angles And Uniformity
- Dell P2815Q: 4K On The Cheap (With A Caveat)

To say Dell's customer service is bad would actually be a compliment to them. They have no means of repairing their monitors and do not supply service information to enable anyone else to repair them either.
Stay away from Dell unless you want a pile of junk and a headache to go with it.