Picture Quality

The Cooler Master Tempest GZ2711 features a 27-inch widescreen 10-bit OLED panel, manufactured by LG Display, with a native resolution of 2560x1440, giving it a dot pitch of 0.2335 mm (108.79 PPI). For the longest time, 27-inch 1440p monitors were considered to offer an ideal balance of image sharpness, screen real estate, and "manageability" of the resolution when it came to gaming; there are drastically fewer pixels to push compared to 4K resolution, and the image is noticeably sharper than in Full HD. To anyone with limited desk space, I'd still recommend getting a 27-inch 1440p monitor over pretty much anything else, especially if you're into gaming. For content creation and other types of work, you might find it beneficial to opt for a 27-inch 4K monitor, although then you have to swallow a noticeable price hike compared to 1440p models.

When discussing the image sharpness of the Cooler Master Tempest GZ2711, as well as any other monitor equipped with a WOLED panel, we have to consider the issue of fringing. WOLED panels, like the one this monitor is based on, have a nonstandard Red-White-Blue-Green (RWBG) subpixel layout, which causes fringing around text; operating systems expect an RGB subpixel arrangement when rendering text. This fringing presents as if text elements have a thin shadow added to them, making them look slightly out of focus and softer than expected. Fringing can manifest in various colors and in many situations, most commonly on the edges of icons and fonts displayed on a bright background. To find out more about fringing in general and see some great examples of WOLED and QD-OLED panel fringing issues, I recommend you check out an excellent article published by PC Monitors. For gaming, video, and similar types of usage, fringing isn't an issue you should be worried about. However, if you mostly work with text and graphics, especially on a professional level, this could be a reason to steer clear of OLED monitors altogether. At higher resolutions and pixel density, this type of fringing becomes less of an issue.

The Cooler Master Tempest GZ2711 doesn't have a traditional LED backlight unit. Individual pixels of an OLED panel are self-emitting, and that's where many of the benefits of such panels; infinite contrast, perfect blacks, absence of haloing, and superb response time, come from.

Like other such monitors, the Cooler Master Tempest GZ2711 uses a fairly heavy matte screen coating. It does a very good job of reducing reflections and preserving OLED blacks even in bright conditions. With SDR brightness being the biggest challenge for all OLED monitors currently on the market, having a screen coating that manages to preserve it in difficult surroundings is hugely beneficial. The picture isn't perceived as grainy or dirty from a normal sitting distance.

In case you skipped the previous pages of this review, allow me to reiterate an important characteristic of the Cooler Master Tempest GZ2711: this monitor offers no way of deactivating the Auto Brightness Limiter (ABL). If you can't get used to the fact that the brightness of the panel constantly (and visibly) changes depending on what's shown on the screen, then this will be a dealbreaker for you. Most other OLED monitors let us turn this feature off to get a constant level of brightness at the expense of maximum brightness, which gets locked to around 200 cd/m². For most users – myself included – that's an acceptable compromise. Future owners of the Cooler Master Tempest GZ2711 simply don't have the luxury of choice, as ABL is always on, and there's nothing you can do to deactivate it. I wouldn't call it aggressive at all, but it's definitely there. There's no chance Cooler Master will add the ABL toggle in a future firmware update either, because the monitor's firmware unfortunately isn't upgradeable, another caveat.

To test the picture quality of the Cooler Master Tempest GZ2711, 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

I tested the picture quality of the Cooler Master Tempest GZ2711 at its factory defaults right after plugging the monitor in and allowing the panel to warm up for about an hour.


At default settings, the Cooler Master Tempest GZ2711 has a color temperature of 6,197 K, an average grayscale color accuracy of ∆E 2.6, and an average gamma of 2.293, although the actual gamma curve is all over the place. In the 0-60 level range, the measured gamma is much higher compared to the reference, resulting in a certain loss of finer dark detail. Then it drops below the reference, only to go over it again in the 90-100 level range. All 27-inch WOLED gaming monitors I've tested to this date have a sub-par default gamma curve, and this is something you can't fix without proper hardware calibration of the monitor either. Gamma-related issues aren't likely to be spotted with the naked eye, primarily because you don't know what you're missing when you can't see it, but that doesn't mean they're not worth mentioning. The RGB balance is off as well – the blue channel obviously needs more gain. As for the luminance, it oscillated depending on the amount of bright content shown on the screen, but it managed to stay above 200 cd/m² for the most part, which means that the Tempest GZ2711 is completely usable in a normal home environment even with the Auto Brightness Limiter forcibly enabled. Compared to the Acer Predator X27U, which matches the Cooler Master Tempest GZ2711 price-wise, the Tempest GZ2711 offers better out-of-the-box grayscale accuracy, RGB balance, and gamma. On the other hand, most competitors, except for the KTC OLED G27P6, let us deactivate ABL and use the monitor with a constant luminance.


The default color accuracy, when tested within the sRGB color space, isn't ideal, primarily because of the significant oversaturation of reds and greens, caused by the wide gamut of the WOLED panel. However, it's much better than what I saw when testing the Acer Predator X27U (average ∆E 3.07 vs 4.2, and maximum ∆E 6.26 vs 7.16).


The CIE diagram shows 100% coverage of the sRGB and a 95.3% coverage of the DCI-P3 color space. The measured gamut volume equals 145.2% for sRGB and 102.9% for DCI-P3 color spaces.


The monitor offers a dedicated sRGB color mode (Color Adjust > Color Mode > sRGB). Unfortunately, it's not tuned properly, so you gain nothing from using it – the color temperature is worse than in the default Native mode, as are the grayscale and color accuracy, average gamma, RGB balance, and even color gamut. On top of that, using the sRGB mode locks you out of changing settings like color temperature (understandably), contrast, and black stabilization, as well as using HDR.

What you should do instead is adjust the color temperature manually. This is done by going into the Color Adjust > Color Temperature menu, selecting the User Color option, and then adjusting the individual channel gains. I got the best results by leaving the red channel at 100 while lowering the green channel to 98, and the blue channel to 84. This might strike you as odd considering our initial measurements showed that the blue channel gain is too low. The thing is, as soon as you select the User Color option, the white balance changes completely from the default setting, so you're no longer working with the same numbers. This was the only change I had to make. The brightness was already set to 100, which is where you should keep it, and there's nothing else in need of adjusting.

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



After adjusting the settings as described we see improvements to all aspects of the image quality. The RGB channels are now much more in line with each other, the white balance is very close to ideal, and overall color accuracy improved, too. The average gamma is better as well, although the curve still looks pretty far from ideal. As I've already mentioned, this is something that needs to be tackled with hardware calibration. Overall, after the aforementioned color temperature tweak, the Cooler Master Tempest GZ2711 shows an attractive picture, which is bound to make gamers salivate in excitement. The OLED-specific deep, punchy colors and inky blacks are a treat for the eye.


This is what the luminance and color uniformity of the Cooler Master Tempest GZ2711 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. There's of course no backlight bleed anywhere on the screen, because there's no traditional backlight that could cause it. The contrast deviation is higher than usual, rising up to 14.04% in the bottom left corner of the panel, but staying below 10% everywhere else. The brightness uniformity isn't stellar either – we see that the upper and bottom edges have trouble staying at the same brightness as the middle of the panel. Of course, some of this can be attributed to the ABL-always-on nature of the Cooler Master's monitor. All these deviations are hard to spot with the naked eye, but they're something you should be aware of if considering this monitor for serious, color-critical work. For such purposes, it simply isn't a good choice – none of the 27-inch gaming OLEDs are.

Picture Quality After Calibration

I calibrated the display using the X-Rite i1Display Pro colorimeter and the DisplayCAL software solution.

Here's what we get after calibrating the monitor.



OLED monitors are much harder to calibrate than LCD monitors are, but we still see great improvements in both color accuracy and gamma tracking.

HDR Performance

Because of their technological characteristics, OLED monitors, including the Cooler Master Tempest GZ2711, are a great choice for HDR gaming and content consumption. After detecting an HDR signal, the monitor automatically enters an HDR mode, which prevents you from adjusting some of its settings, including brightness, color modes, and color temperature.


Depending on the amount of bright content on the screen, the monitor will reach brightness peaks of close to 700 cd/m² for 1% white window sizes. At 10% window size, you can expect around 500 cd/m², dropping to 120 cd/m² for full-screen sustained brightness (100% white). These values are lower than what we saw on competitors such as the Corsair Xeneon 27QHD240 and the KTC OLED G27P6. However, they're still high enough to make the HDR content look impactful.


The EOTF performance is off by quite a bit; the picture will be brighter than needed in the 0-60 level range, and then dimmer than required by the input signal up to a level 100 (pure white). The RGB balance is less than ideal in HDR mode, too. The blue channel has way too much gain and is responsible for most of these issues, even without bringing luminance into the equation.

Viewing Angles

The viewing angles of the WOLED panel built into the Cooler Master Tempest GZ2711 are excellent. There's no visible shift in colors from any sitting position or when changing positions.

OLED Burn-in Prevention Features

The burn-in prevention features of the Cooler Master Tempest GZ2711 are found in the Setup Menu > OLED Protect menu. Here we have a standard manual pixel refresh cycle toggle, which is offered by every monitor equipped with the same LG Display's WOLED panel, as well as two additional options: Screen Shift and Logo Luminance Adjustment.

Screen Shift is a feature that automatically shifts the image by one pixel per minute in a circular pattern while you're using the monitor. This is a way to fight against static UI elements. Some find such features distracting and undesirable, but I have to admit I barely noticed it while using the Tempest GZ2711.

The Logo Luminance Adjustment feature looks for static UI elements and makes them dimmer. This could be the scoreboard in Rocket League, the spell menu in World of Warcraft, or anything else that's being permanently displayed on the screen. Depending on the game you're playing, you might want to consider turning the Logo Luminance Adjustment off, for added visibility.