Picture Quality

The AOC U28G2XU2 features an 8-bit IPS panel capable of displaying 16.7 million colors. It's the Innolux M280DCA-E7B panel, used by many other 28-inch 4K 144 Hz monitors, such as the Gigabyte M28U and the Asus TUF Gaming VG28UQL1A. The W-LED backlight unit is controlled by direct current (DC), which makes it flicker-free at any given brightness level.

The screen coating on the AOC U28G2XU2 is light anti-glare (AG). The screen is decently resistant to reflecting its surroundings even when used in a room with a lot of natural or artificial light, and the picture isn't perceived as grainy or dirty from a normal sitting distance, which can be the case with heavier AG coatings. The maximum specified brightness of the panel is 370 cd/m², accompanied by a static contrast ratio of 1,000:1.

Image sharpness is one of the best aspects of the AOC U28G2XU2. A combination of a 28-inch diagonal screen size and 4K resolution results in a high pixel density of 157 PPI. Everything looks impressively sharp on the U28G2XU2, from text and icons to games and video content. Websites and documents look outstanding, with a crispness that cannot be matched by monitors with lower pixel density. As for the available screen real estate, Windows automatically recommends 150% image scaling, which means you're effectively getting the same amount of room as you'd get with a 2560x1440 resolution at 100% scaling. Eagle-eyed users could get away with lowering the scaling to 125% to get more screen real estate, but if your vision isn't 20/20, setting it to 150% is pretty much mandatory.

To test the picture quality of the AOC U28G2XU2, I've used a combination of the X-Rite i1Display Pro, DisplayCAL – a powerful software solution for display calibration and profiling, which is completely free to use, assuming you own a supported colorimeter – and Calman, the industry-standard display testing and calibrating software suite.

Picture Quality at Factory Settings

The picture quality of the AOC U28G2XU2 at its factory defaults was tested right after plugging it in and allowing it to warm up for about an hour.


At default settings, the AOC U28G2XU2 has a color temperature of 6,312 K, a contrast ratio of 984:1, and an average gamma of 2.151. The average grayscale accuracy shows a deviation of 1.8. These are decent values, although we do see a significant imbalance in the blue color channel, which is something that will have to be addressed by adjusting the color temperature settings manually. The measured gamma is slightly higher than required by the input signal in the 0-30 range, and then lower than needed from there onwards. This does cause some crushed shadow detail in darker content and a loss of finer details in brighter content, but the issue isn't too pronounced.


The default color accuracy, when tested within the sRGB color space, isn't particularly good. The average ∆E is 3.62, and it raises up to 6.37. The CIE graph shows us what's causing this deviation: we get a significant oversaturation of all three primary colors in the sRGB color space, with the red one being the biggest offender.


The quickest way to get an improved overall picture quality, especially in the color accuracy and gamma tracking departments, is to set the monitor to sRGB mode in the OSD (Color Setup > Color Temp. > sRGB). The color temperature in sRGB mode is still lower than it should be though, so the grayscale accuracy naturally suffers. What's more problematic is that using the sRGB completely locks you out of changing any other settings, including brightness, which is locked at 150 cd/m² – too low for average home users and their uncontrolled environments. For that reason I can't recommend using the sRGB mode.

You're best off manually adjusting the brightness and individual color channels to improve the white balance and other aspects of the image quality. The white balance can be improved by visiting the Color Setup menu in the OSD and changing the Color Temp. setting to User. That gives you access to individual RGB color channels. To get the white balance closer to 6,500 K, I had to set the red channel (R) to 43, green (G) to 40, and leave the blue (B) one at 50. Remember, our initial measurements showed that the blue channel gain is far too low compared to red, so this is why the custom RGB channel gain settings look a bit unusual. Afterward you can adjust the brightness (Luminance > Brightness) to your liking and environment. Setting it to 93 will put you at around 250 cd/m², which is a good middle ground for combined daytime and nighttime usage.

Let's compare the measurements before and after doing the OSD tweaks.



After adjusting the settings as described above we see improvements to the white balance, a much better RGB balance, and vastly increased grayscale accuracy (∆E down to 1, from 1.8). The color accuracy improved as well, but the gamma didn't, which isn't expected anyway, as gamma tracking issues are very hard to correct without calibrating the monitor. The measurements show all these improvements nicely, but it's also worth pointing out that the picture looks much better to the naked eye as well, after doing nothing but the aforementioned OSD tweaks. To push things even further, a calibration is mandatory, as you'll soon find out.


As we can see by examining the CIE diagram, we get a 98.5% coverage of the sRGB and an 83.7% coverage of the DCI-P3 color space with our adjusted settings. The gamut volume equals 123.8% for sRGB and 87.7% for DCI-P3 color spaces.


This is what the luminance and color uniformity of the AOC U28G2XU2 look like when measured at 25 different patches across the panel. Please click on the image to see it in high resolution and examine the data in greater detail. Both the contrast deviation and brightness stability look good. The colorimeter picked up some darkening happening on the left edge of the panel, but the deviation stays within -8% on average, which means it's unlikely you'll ever spot it with the naked eye.

The AOC U28G2XU2 carries a VESA DisplayHDR 400 badge, meaning it can achieve a peak luminance of 400 cd/m² in HDR mode. However, the monitor lacks a backlight local dimming technology, which is essential for a true HDR experience, so it's not a viable option for proper HDR gaming or video content consumption.

Picture Quality After Calibration

I calibrated the display by using the X-Rite i1Display Pro colorimeter and the DisplayCAL software solution. The initial profiling and calibration were done with the luminance target set to 250 cd/m², which presents a happy medium for a comfortable combined daytime and nighttime usage.

Here's what we get after calibrating the monitor.



A proper hardware calibration results in big improvements in color accuracy and gamma tracking. The average color accuracy deviation went down to ΔE 0.47, although I wasn't able to get the blue color, as well as its shades, to display perfectly, even after calibration. This is obvious by looking at the measured color accuracy values and the recorded ΔE of 4.16.

Backlight Uniformity

To give you an idea of the backlight's uniformity, I set the brightness of the monitor to 250 cd/m² before taking a photo of the panel in a completely dark room. I did my best to find a combination of the ISO value and shutter speed that would capture the screen in a way that has it look as close to what my eyes were seeing in real life.


There's some backlight bleed on both top and bottom corners of the panel. Luckily it's only visible when very dark content is being displayed.

Viewing Angles

The viewing angles of the IPS panel built into the AOC U28G2XU2 are excellent. There's no visible shift in colors when you change your sitting position.