Miniled for Less Review – Cooler Master GP27U and AOC AG274QXM

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A gaming monitor with good HDR: it remains a difficult story. If you go to the Pricewatch now, you will find exactly 300 available screens with some form of HDR support , with the cheapest option only costing 159 euros. Unfortunately, support for such affordable models is often limited to understanding the signal. If you want to make an LCD monitor that can properly show the high contrasts of an HDR image, you need a full array local dimming backlight, or false backlight, that can make parts of the image brighter or darker where necessary.

The first LCD monitors with HDR and Fald backlight date from 2018. These were 27″ models based on a 4K panel, with 384 separate LEDs behind them. MiniLEDs enable more efficient production and even finer local dimming. At CES The first monitor with mini LED backlight was already presented in 2019, which slowly trickled into the shops in the following years.In 2021, for example, we discussed the ASUS ROG Swift PG32UQX and the Samsung Odyssey Neo G9 .

Finally not extremely expensive

As more and more mini LED screens reach the market, there are also a few that are not as extremely expensive as the previous screens from ASUS and Samsung. For example, while the PG32UQX had to pay no less than 3499 euros, the Pricewatch already has more than 10 miniLED screens below the 2000 peak, with more models on the way. In this article, we take a look at two of the cheapest mini-LED monitors out right now, which should even cost less than $1,000: the AOC Agon Pro AG274QXM and the Cooler Master Tempest GP27U. This makes them cheaper than the OLED monitors for gaming that were announced by various manufacturers at CES and they could also be interesting if you are looking for a monitor with excellent HDR reproduction.

The Tempest GP27U appeared at the end of November last year for exactly 999 euros, although it now seems to be sold out. For that you get a 27″ 4k monitor (3840×2160) with a 160Hz refresh rate and the expected HDMI 2.1 connections for your console. These specifications resemble the quartet we reviewed earlier, but behind the IPS panel of the Cooler Master screen is a mini LED backlight with 576 zones, which should be able to deliver a brightness of around 1000cd/m².

AOC’s screen was already announced in the fall of 2021 and has been on the market for about a year now. The starting price was 1049 euros, but it is now available for only 678 euros at the cheapest provider. It competes with the Cooler Master Tempest GP27Q, the sister model of the GP27U that we look at in this article. The AG274QXM and GP27Q have a 27″ wqhd panel (2560×1440), which in any case produces a somewhat less sharp display than with the GP27U, but many of the other specifications are the same. The AG274QXM also has an IPS panel with local dimming with 576 zones and a brightness of 1000cd/m², with the refresh rate at 170Hz being slightly higher.

Considering the differences in resolution and price, the AG274QXM and GP27U are not directly comparable, but on paper you get an advanced monitor for a relatively competitive price. To assess whether these ‘miniled screens for less’ are also a good buy in practice, they go through our extensive test course.

Feature set and practice

The AOC Agon Pro AG274QXM has the angular design that AOC introduced a few years ago for its Agon series. Like many other gaming screens, the panel rests on a tripod. The legs at the front protrude quite far, while the small leg at the back has a hole through which you can route cables. The vertical upright has a rectangular design, with the attachment point between the screen and the leg having a bright red colour. The handy carrying handle at the top of the leg is also finished in the accent colour. There are stripes on both sides of the panel with integrated RGB LED lighting, which can clash quite a bit with the pronounced red-black color scheme of the screen.The panel is clearly thicker than with a normal monitor, with ventilation slots around the side that also prove necessary in practice:

The Cooler Master Tempest GP27U does not get as hot when used and has a much smarter design. You wouldn’t say there are 576 LEDs behind the panel instead of thinner edgelit backlight lighting, as with most screens. On the back of the panel are wing-shaped ventilation slots with RGB LED lighting above. The GP27U also has a ring of LED lighting around the base attachment point, similar to what Samsung does with its Odyssey displays. The panel rests on a base that is also not very large: a round leg with a base in the shape of the hexagonal Cooler Master logo. Both parts are made of dark gray metal, with a plastic clip that can be attached to the leg to route cables. As with the AOC screen, the leg is clicked onto the screen without screws.

The build quality of both screens feels fine. The AG274QXM is even more stable on the desk thanks to the wide front legs. Adjustment options are endless. The AOC screen offers 120mm of height adjustment and Cooler Master’s monitor can be raised and lowered by 110mm. In addition, both the AG274QXM and the GP27U can pan, tilt and rotate to portrait orientation.

Apart from RGB, the GP27U has no special features on the housing, but the AG274QXM does have many extras. For example, AOC supplies a wired hockey puck-shaped remote control with its screen to operate the OSD. There is an extendable headphone hook on the left side of the monitor, and there is a built-in projector in the leg with which you can project a logo of your choice on your desk. As far as I’m concerned, that’s a totally unnecessary feature, and besides, the projector is in an inconvenient place, if you like it. The lens in the middle between the front legs is easily blocked by cables if you use the recess in the base for cable management. Also striking about the AG274QXM is the included lens hood.That is mainly something you see with screens for graphic artists, although miniLED monitors sometimes have it more often.


Both the AOC AG274QXM and the Cooler Master GP27U have a large number of four video connections: two HDMI, one DisplayPort and one USB-C, whereby the screen receives an image via DisplayPort Alternate Mode. Similar to a business docking monitor , both screens provide full power delivery The AOC AG274QXM can return up to 65W to a connected laptop and the GP27U even offers 90W. The latter will also not be enough for a powerful gaming laptop, but it is sufficient for most ‘normal’ laptops.

Cooler Master’s display also features a two-port USB hub, while the AG274QXM has four USB ports. With both screens they are in a hard-to-reach place behind the screen. In addition to USB-C, both displays have a USB-B upstream port to connect the hub to a second PC. Both screens have some form of kvm functionality on board. Connected peripherals are automatically assigned to the USB-C port when that source is in view, and switched to the USB-B port when one of the other video inputs is selected. It does not seem possible to automatically reassign the USB-C port to a different video connection, for example if you want to connect two desktop PCs that both do not support video output over USB-C.

The HDMI 2.1 ports on the Cooler Master GP27U support the full bandwidth of 48Gbit/s, which allows the screen to operate at full 4k resolution and 160Hz refresh rate via all connections. The AG274QXM still has HDMI 2.0 ports with a lower bandwidth of 18Gbit/s, which is not so bad in this case because the screen does not have a 4k resolution. It does mean that 144Hz over HDMI is the maximum. As with the GP27U, Adaptive Sync , in both cases from 48Hz, also works over HDMI.

AOC and Cooler Master have simple speakers built into their screens, with the Cooler Master GP27U having a 3.5mm headphone port on the connection panel, while the AG274QXM has separate headphone and microphone connections. Both screens have an external power supply. Not ideal as far as I’m concerned, certainly not with the AG274QXM, where the separate power block is an extremely unwieldy colossus.


For operating the OSD, the AG274QXM and GP27U both have a five-way joystick on the right behind the panel, with the AOC screen, as mentioned, a wired remote control as a second option.

The OSD of the AG274QXM is designed vertically. The division of options over categories could have been more convenient in my opinion. For example, the setting for local dimming is not in the ‘luminance’ menu, image modes for hdr and sdr can be found in other sections of the menu and the setting to limit the color range to sRGB is under ‘color temperature’. The AG274QXM has a remarkable number of settings for the sound. There is an equalizer with five bands and various presets, such as Rock or Classic. There are also detailed options in the OSD for adjusting the color and effects of the RGB lighting, although it is better to use the updated G-Menu application for this. It also allows you to synchronize the lighting with other AOC peripherals,

The GP27U has a more traditionally styled three column display menu. Confusingly, the third column sometimes shows an overview of currently selected options and sometimes a submenu of available options. They are more detailed with Cooler Master than with AOC, at least when it comes to the image. For example, the intensity of the local dimming can be adjusted in multiple levels, there are options to adjust hue and saturation for both primary and secondary colors, and the color range can not only be adjusted to sRGB, but also DCI-P3 or AdobeRGB . The settings for the overdrive are also very extensive. As with AOC, you can optionally put a reticle or fps counter over the image. The settings for the RGB on the back are very minimalistic: ‘on’ or ‘off’,

Test method and test field

Portrait Displays SpectraCal C6 Colorimeter

For this review, as usual, we took an extensive series of measurements. We measure brightness, contrast and color rendering using a Spectracal C6 colorimeter, which we profile using a JETI Spectraval 1501 Hires spectroradiometer. Measurements are performed using Portrait Displays Calman Color Calibration software. We recently updated the testing procedure, which you can read more about in this .plan. Here we measure the screen as it comes out of the box, adjusting the brightness for color measurements to a value that is as close as possible to 150cd/m². In addition, we set the screen for color spaces such as sRGB and, if relevant, Display P3 and AdobeRGB. We also make adjustments to the gamma and color temperature if necessary.

We measure response times with a photo sensor and the LeCroy Waverunner 6100 oscilloscope. We ran more extensive response time tests for this article, measuring 20 transitions. We determine the input lag with a Leo Bodnar tester, sending 1080p-60Hz signals to the screen in addition to 1080p-60Hz. To determine viewing angles, we measure residual brightness and color change at a 45-degree angle from a perpendicular measurement. For the uniformity measurement, we look at the ratio between the brightness at fifteen measuring points, measured on a completely white and a completely black screen. We also determine the relative color differences along the edges in relation to the center. Finally, we measure the energy consumption of the monitor,

Test field

We compare the AOC Agon Pro AG274QXM and Cooler Master Tempest GP27U to a range of other high-end gaming monitors. Some of them have a wqhd resolution, such as the AG274QXM, others have a 4k panel, such as the GP27U. The 4k screens can be recognized by a light blue bar in the graphs. These screens are often cheaper than the AG274QXM and GP27U, but they do not have a mini LED backlight, fine-grained local dimming or very high brightness for HDR display.

The overview also includes two OLED monitors and LG’s 65C24LA OLED television. They have a different diagonal than the screens in this article and also cost much more. They are among the best HDR screens we’ve tested to date, along with the miniLED screens in our test file, such as the Samsung Odyssey Neo G9 (LS49AG950NUXEN), ASUS ROG Swift PG32UQX and ASUS ProArt PA32UCX-PK. These monitors are also reflected in the charts, and are or were much more expensive than the duo from this article.


Brand and product range AOC Agon Pro Cool Master
Type AG274QXM Tempest GP27U
Price and appreciation
Price €689 (17 stores) Unknown (2 stores)
First price listing Tuesday, November 9, 2021 Wednesday, November 30, 2022
Valuation Rating: 0 Rating: 2
Screen diagonal 27″ 27″
Curved screen No No
Display coating Matt/anti-glare Shiny
Resolution 2560×1440 (Quad HD) 3840×2160 (4K)
Horizontal resolution 2560px 3840px
Vertical resolution 1440px 2160px
aspect ratio 16:9 16:9
Pixel density 109ppi 163ppi
Panel and backlight
Type of panel lcd lcd
LCD panel Ips Ahva ips
backlight Miniled Miniled
dimming Full-array local dimming (miniled) Full-array local dimming (miniled)
HDR support HDR10 HDR10
DisplayHDR 1000 1000
Response time 1ms 1ms
Refresh rate 170Hz 160Hz
G sync support G-Sync Compatible (Certified) G-Sync Compatible
FreeSync support FreeSync Premium Pro FreeSync
FreeSync minimum refresh rate 48Hz 48Hz
FreeSync max refresh rate 170Hz 160Hz
Imaging technique
Viewing angle 178° 178°
Brightness 600cd/m² 600cd/m²
Brightness (peak) 1,200cd/m²
Contrast ratio (static) 1,000:1 1,000:1
Color depth 10bit (1.074 billion) 10bit (8bit + FRC) (1.074 billion)
Video in DisplayPort, 2x HDMI, USB 3.2 (Gen1, 5Gb/s) type-C DisplayPort, 2x HDMI, USB 3.2 (Gen1, 5Gb/s) type-C
Total video inputs 4x 4x
Highest HDMI version HDMI 2.0 HDMI 2.1
Highest DisplayPort version Display Port 1.4 Display Port 1.4
Outputs (Monitors) 3.5mm 3.5mm
USB hub (downstream) 4x USB 3.2 (Gen1, 5Gb/s) 2x USB 3.2 (Gen1, 5Gb/s)
USB Power Delivery Yes Yes
USB Power Delivery max 65W 90W
Number of speakers 2.0 2.0
Total speaker power (RMS) 5W 4W
Ergonomics Rotatable on foot, Height adjustable, Vertically tiltable, 90° horizontally rotatable (Pivot) Rotatable on foot, Height adjustable, Vertically tiltable, 90° horizontally rotatable (Pivot)
Bracket mounting Vesa 100mm Vesa 100mm
Height 547.3mm 525.9mm
Adjustable height 120mm 110mm
Height (without foot) 368.2mm 364.2mm
Width 612.9mm 617.8mm
Depth 352.1mm 273.7mm
Depth (without foot) 73mm 64.8mm
Weight and color
Weight 8.15kg 5.1kg
Colour Red Black Black
Warranty and details
Manufacturer’s warranty 3 years carry-in 2 year carry-in

Response time and input lag

As described on the Test method page , we usually perform a response time test on gaming monitors with twenty transitions, where we also measured transitions between different shades of gray and from black to dark gray. We were able to perform this test without any problems on the Cooler Master Tempest GP27U. You can see the results below. With the AOC Agon Pro AG274QXM, we were unable to measure the response times properly, so the screen is missing from the graphs. This has to do with the control of the backlight.

Nowadays, the backlight is controlled flicker-free in almost all LCD monitors. The lights are on continuously, even if you lower the brightness control. That makes viewing the screen more comfortable; some people are sensitive to low-flicker PWM dimming, which was common a decade or so ago with the first generation of LED-backlit LCD monitors. Manufacturers then not only applied pwm dimming because it was cheaper to implement, but also because LED lights can suffer from color shift if you adjust the brightness by reducing the voltage. Perhaps that is the reason that pwm dimming is used again in the screens in this article. Controlling 576 lights is already complex enough,

With the Cooler Master GP27U, the lights are constantly on as long as you don’t use the local dimming feature, a well thought-out function for those who want to use the screen for both gaming and office work. If you enable local dimming, pwm dimming is applied. The AOC AG274QXM never uses flicker-free dimming, even if local dimming is off. We also see a strange pattern of brightness fluctuations with this screen: it is not simply ‘on off, on off’, as with the GP27U and OLED screens. That also makes it difficult to measure the response times of the panel manually, which we do for OLED screens, for example. The automated functions of our oscilloscope for measuring rise and fall times, for example, only work well with a screen with a continuously burning backlight.

A review of gaming monitors minus the response times section doesn’t make much sense, but thankfully there’s an alternative to our regular measurements. The website Blurbusters has developed a test method to visualize what moving images look like on different screens, using a special test pattern that must be followed with a moving camera at exactly the same speed. Below you can see the result. We have set each screen to the maximum refresh rate. The first photo shows the overdrive off, the second photo shows the maximum overdrive setting and the third photo shows the overdrive setting, which we believe provides the best balance between fast response times and little overshoot.

At the optimal settings, both screens offer fast response times, it can be seen. The UFOs stand out nicely against the background, in which only a little bit of ghosting can be seen on the darker color. With the AOC AG274QXM, the UFO looks slightly sharper than with the Cooler Master GP27U. If we look at the measurement, it appears that the GP27U also scores well compared to other screens. In fact, its average response time of 2.7ms makes it one of the highest-scoring 4k gaming monitors we’ve tested.

Both screens have different overdrive modes. With AOC it’s easy: you have the options ‘Off’, ‘Weak’, ‘Medium’ and ‘Strong’. The response times even look pretty good on the lowest setting, with Weak offering a slightly sharper image; we have therefore chosen this option as the optimal position. If you go further, a lot of ugly inverse ghosting becomes visible. The amount of overdrive seems to be adjusted according to the refresh rate. Even at 60Hz, the ‘Weak’ setting still offers the best balance between response times and overshoot.

The OSD of the GP27U gives many options to adjust the overdrive to your taste. Maybe a little too much. The game menu offers six options, with four presets to start with, from Off to Normal, Advanced and Ultrafast. The third offers the best balance. On top of that, there’s the ‘User’ option, which lets you adjust the overdrive in 101 steps. I don’t know of any other monitors where you can set the overdrive so precisely. That this menu doesn’t seem to have the same scope as the presets undermines its usefulness. Ultrafast gives even faster response times and more inverse ghostingthan the 100 setting in the User menu. In addition, the overdrive in the mentioned presets and the User menu does not work dynamically based on the refresh rate. For that you need to use the ‘Dynamic’ option, the last of the six in the game menu. ‘Dynamic’ offers hardly any slower response times at 160Hz than ‘Advanced’, but at 60Hz the balance between response times and overshoot remains intact. So I would recommend that stand.

Both screens do not offer a motion blur reduction option to further improve motion sharpness. It is striking that the cheaper brother of the Cooler Master GP27U, the GP27Q with wqhd panel, would have this option .

A less desirable form of flickering that sometimes occurs with gaming screens is flickering when using a variable refresh rate. The AG274QXM seems to have little or no problems with this, but there is more going on with the GP27U. With local dimming off, the brightness is stable, but with local dimming switched on, I certainly saw flickering in the image with HDR images when the refresh rate fluctuated between 60Hz and 100Hz. This could be due to the Nvidia video card in our test system; the GP27U is not officially G-Sync Compatible like the AG274QXM. According to the manufacturers, both screens should support FreeSync Premium Pro.

Input lag

To determine the input lag, the amount of delay before an image sent to the monitor actually appears, we use a Leo Bodnar input lag tester. It is placed in the center of the screen. By default, we send a 1080p-60Hz signal to the screen and that produces the graph below. Both monitors suffer little from input lag.

Default display: brightness, contrast and color

Before we look at the color reproduction, we first assess the maximum and minimum brightness of the screen, as well as the contrast. By default, local dimming is disabled for both screens in SDR, and that’s how we tested the screens. Both AOC and Cooler Master do give you the option to turn it on for SDR image. The contrast can of course improve considerably, but on the desktop you see clear haloing and brightness differences. I would only use it for a movie or game.

Also in sdr and without local dimming, the AOC Agon Pro AG274QXM and Cooler Master Tempest GP27U are brightness cannons. On a completely white screen, both screens achieve a brightness of more than 600cd/m² with the brightness control set to 100. The average LCD monitor only comes up to half, and OLED screens only achieve a third to a quarter of this brightness when viewed full screen. The minimum brightness of both monitors is a slightly less impressive 80cd/m². The average LCD monitor can be adjusted to 60cd/m², and some screens go much darker, which can make all the difference for the darkest rooms.

The native contrast of both monitors is approximately 1000:1. A completely expected result for an IPS panel, but it is not good. Despite the slightly higher measurement value, the GP27U will in practice look a bit less contrasty than the AG274QXM, because the Cooler Master screen suffers a lot from ips glow. The black value rises faster when viewed from an angle.

Color rendering in standard mode

We first test the screen almost without adjustments straight out of the box, with only the brightness at 150cd/m². Because we do not adjust anything else to optimize the performance of the screen, the screen is emphatically not set to its best position. That logically does not yield the best results in the graphs below, only the ‘out-of-the-box’ performance. Keep that in mind when viewing the results.

Both the AG274QXM and GP27U can display a very wide color gamut, and do so out of the box. The gamut is most similar to AdobeRGB, which is almost completely covered by both screens, but has extra saturation in red compared to AdobeRGB and therefore also includes DCI-P3, which is relevant for HDR material. Because the range falls between the two gamuts, it is not well matched for either option, resulting in a high variance in the primary colors. Both screens are stiff at the bottom of the chart.

Unfortunately, the further adjustment is not much better. With a color temperature well above 7000K, the image of the GP27U is too bluish, while the AG274QXM shows a red color cast. The AOC monitor also has a different gamma display, with an average of 2.03 instead of the desired 2.2. This means that shades of gray are shown too light, making the image look duller than intended. Also considering the average gray deviation and color checker deviation, a test that includes both saturated colors and mixed colors and gray values, the AG274QXM and the GP27U do not score well.

For the sake of completeness, we present the measurement results in the old ΔE 2000 values. Both screens also end up in the lower regions in this graph set, but the GP27U clearly scores worse than the AG274QXM here. This is explained by the fact that the GP27U makes more errors in the hue and saturation of the colors, while the ΔE 2000 calculation gives them a greater weight than the deviations in the brightness of colors and grayscale, which occur with the AG274QXM.

Display sRGB, Display P3 and AdobeRGB

From now on, we will measure all screens in the sRGB color space, the gamut for which most content is created. Both screens have a position to better adjust the display accordingly. Unfortunately, with the AOC Agon Pro AG274QXM all further settings are locked, not only options to tweak gamma and color temperature, but also the brightness control. That is a great shame, because a brightness of 335cd/m² makes this mode not pleasant to use if you place the screen in a darker room. Conversely, you cannot use the extra high brightness that this screen has to offer as standard. For some reason, monitors from AOC and Philips have this annoying limitation more often.

The test results show that both screens dial back their wide color gamut a bit too far in sRGB mode. The AG274QXM lacks a bit of saturation in the red and the GP27U also lacks a bit of saturation in green. This is hardly visible in practice. Optimized for sRGB display, both screens offer lower contrast than in standard mode. With the GP27U, the contrast drops even more than expected: we now measure about 800:1. So are the DCI-P3 and AdobeRGB presets we used for the measurements further down this page.

Based on the ITP results, both monitors offer above-average sRGB rendering. In the color checker test in the chart below, they occupy third and fourth positions. With the AG274QXM, the display of primary colors is slightly more accurate. When it comes to the gray display, we see the same image as in standard mode. Cooler Master’s screen offers a better gamma representation, but a less neutral gray gradient. With our settings, the image is now not too blue, but a bit too red. Conversely, gray tones look neutral on the AOC monitor, but the gamma is again a bit too low. It’s better than in the standard view, but enough for the average gray and color checker deviation to be close to the Tempest GP27U.

Due to the way the ΔE 2000 calculation works compared to the ΔE ITP calculation, in combination with the specific deviations of these screens, the GP27U scores relatively worse in the overview below than in the ITP graphs. The average gray deviation even goes towards 5, and you can hardly consider that a good result. So there is still some room for improvement with this monitor.

Display P3

As mentioned, both screens have a color range that goes well beyond Display P3. Unfortunately, the AOC Agon AG274QXM does not offer a preset to properly adjust the screen to this color space, only for sRGB. Based on the native color range of this screen, red and especially green are much too saturated, which increases the average color and color checker deviations with this monitor. It’s a pity that AOC didn’t provide its monitor with more options to adjust the colors to your liking, such as Cooler Master, which did add a preset for this color space. You can still have the AG274QXM display the correct colors by enabling a color profile in Windows, but in practice that does not always work as well as a preset in the OSD that always works.

The DCI-P3 preset of the GP27U can also be used for Display P3, which we test it on. The difference between DCI-P3 and Display P3 is a different gamma value, 2.2 instead of 2.6, and color temperature. With the GP27U, you can set these settings independently of the chosen color space. Again, the gamut coverage appears to be a bit on the low side at 93 percent, but the reproduction of primary colors is not bad either. However, the gray display could be better again, with a purple color cast in the image again, but an excellent gamma adjustment. On average, given the color checker score, this yields quite a good result.


The AOC Agon AG274QXM and Cooler Master Tempest GP27U are among the few monitors capable of AdobeRGB display. You can see that from the number of screens in the graphs below. We only measure a screen for AdobeRGB if that color space is roughly in the range they can display. Screens that are only suitable for Display P3 fall short in green.

The AG274QXM also does not have a separate preset for AdobeRGB, which means that the display of primary colors is not quite what it should be. This is particularly reflected in the color red, which is too saturated. The AdobeRGB mode in the GP27U’s menu neatly controls the color red, with the total color coverage coming out at about 95 percent. That’s fine, but not perfect. Otherwise, the measurement is a repetition of moves relative to the result for Display P3 and sRGB display. Grayscales are too red, but the gamma representation is correct, which, in combination with the good representation of primary colors, achieves an excellent color checker score.

HDR view

With their 576-zone local dimming backlight, the AOC Agon Pro AG274QXM and Cooler Master Tempest GP27U offer a much better HDR display than most other gaming monitors. Brightness and color range can come somewhat close to that, but the simple edgelit dimming of most monitors leads to a faded and washed-out display, with bluish-gray shadows. The image of the AG274QXM and GP27U has the dynamics that I recognize from better HDR monitors. Bright highlights, but also deep dark shadows can be in the picture at the same time.

The advantage of an LCD screen with mini LEDs over OLED monitors is the higher brightness, which can make a beach scene, for example, look better. You can see that in the measurement above. Even if the entire screen needs to be white, the AG274QXM and GP27U offer a brightness of around 1000cd/m². That is higher than the average LCD monitor and much higher than with OLED screens. They can reach 1000cd/m² on small white areas, but they go way down on a completely white screen: even below 200cd/m² in the case of the two screens with a woled panel in the graph.

We measure the contrast in HDR with a 4×4 checkerboard with alternating black and white squares. This immediately shows why the HDR display on the majority of LCD screens is so disappointing. Even with this fairly simple image, local dimming on these screens no longer does anything, so that the contrast remains at a lifeless 1000:1. That is far too little for a good HDR display. With the AG274QXM and GP27U, the contrast in the checkerboard test is approximately 1.5 times and approximately 2 times higher than the native contrast of the LCD panel, respectively. With a completely black image, the Cooler Master monitor turns the LEDs off completely, while with the AG274QXM they stay on a little bit, for an on-off contrast value of approximately 30,000:1.

Fald therefore does its job on these monitors, but at the same time the solution has its limitations compared to an OLED screen with individually lit pixels or a more expensive mini-LED screen with many more dimming zones. The two ASUS monitors in the chart achieve a contrast of around 5,000:1 in the checkerboard test, and Samsung’s Odyssey Neo G9 even surpasses 10,000:1. In practice, this means that with the AG274QXM and GP27U you will more often see the typical artifacts such as haloing around high-contrast transitions, where shadows cannot be as pitch black as on an OLED screen or better miniLED screen. The relatively low contrast of the LCD panel used and the amount of ips glowwith the GP27U do not help to hide deviations. With the AG274QXM, a strange shift in the color temperature is noticeable around the transitions from a light to a dark zone. The image suddenly becomes a lot warmer there.

As can be seen from the difference in contrast value, local dimming with the GP27U is more aggressive by default than with the AG274QXM, which can make halo effects visible more quickly. Cooler Master lets you make the trade-off between that side effect and a higher contrast yourself. Via the OSD of the GP27U you can switch between three levels of local dimming, with higher settings further increasing the brightness in bright areas. Even at the lowest setting, the image of the GP27U already has more contrast than the AG274QXM, which does not let you adjust the strength of local dimming.

Not only is the HDR image of the GP27U richer in contrast than that of the AG274QXM: the color reproduction is also much better. In the test results, the AOC monitor even came in last place once. The detailed measurement results show that this is the sum of various deviations. For starters, the image is way too blue. Maybe that’s a choice made to make the image appear brighter, but I’d rather have a correct rendering. In addition, the brightness development of the AG274QXM deviates from the HDR PQ curve, say the gamma curve for HDR material. Dark shadows are too light, while the screen displays midtones too dark. Also because of this, the image on the AG274QXM looks duller than on the GP27U.

The Cooler Master screen offers slightly less detail in the very darkest shadows, but otherwise follows the PQ curve quite well, with a little roll-off around the buckling point where the screen cannot be brighter. That’s exactly what you want to avoid unsightly clipping in clear transitions. There is hardly any color cast in the gray display of the GP27U. In combination with the wide color range, which, as shown by the measurement, approaches that of ASUS’ very expensive mini-LED monitors for creators, this results in a very good HDR color reproduction. It is even better than monitors that are much more expensive.

Both monitors have different presets for HDR color reproduction, just like in SDR. With the AG274QXM, all options except ‘DisplayHDR’ add sharpening to the image that you cannot turn off. The Cooler Master monitor also unnecessarily increases the sharpness in two of the three HDR modes, but you can turn that off with this monitor.

Uniformity and viewing angles

We measure the residual brightness and color deviation of the screens at an angle of 45 degrees. We do this for horizontal viewing angles, ie to the left and right, and for vertical viewing angles, below and above. The AOC Agon Pro AG274QXM scores average in this graph set, but looking at all monitors with an IPS panel that we have tested recently, it is rather below average. For example, the much cheaper LG UltraGear 27GP850 is already doing a lot better, as are many of the 4k screens in this chart.

The Cooler Master GP27U has even worse viewing angles than the AOC monitor, and therefore also a lot worse than those of competing 4k monitors, such as the Gigabyte M28U or Samsung Odyssey G70A. The Sony Inzone U27M90 has comparable viewing angles according to measurements and we already wrote in the review of that monitor that only about 15 percent of all monitors we tested scored even worse.


To assess uniformity, we look at the ratios between the brightest and darkest cells in a four-by-three cell matrix. Please note that these are our review samples; we cannot extrapolate to all monitors.

In ‘normal’ LCD monitors, the backlights are usually on one side, with a system of light guides ensuring that the light falls evenly across the entire panel. That is not a recipe for the best uniformity. We see that the AG274QXM and GP27U with the lights directly behind the panel score a lot better in the tests of white uniformity. The Cooler Master monitor does very slightly better than the competitor, but both screens even manage to beat (QD) OLED screens in the overview.

OLED screens also show perfect black uniformity, and that is less of a success with the AG274QXM. A black image looks remarkably irregular on this screen, at least when local dimming is off. Looking at the backlight photo we take of all screens, overexposed to make aberrations more visible, there is an effect at the bottom of the screen that almost resembles the flashlighting of poorly designed edgelitlocaldimming. It is as if a few flashlights are shining on the panel from the bottom, but that is not the case with this monitor. Fortunately, the monitor has an advanced local dimming feature, which can make the black reproduction a lot better in practice.

The black uniformity of the Cooler Master Tempest GP27U is not of OLED level, but the screen is best of the rest in the graph below. In the backlight photo we took, the black reproduction therefore looks homogeneous, with only a little bit of clouding on the right side.

Power Consumption

We measure the power consumption in two scenarios. First we measure the energy consumption while displaying a white screen with a brightness of 150cd/m². That is the brightness we use for normal use and with which we perform almost all our screen measurements. We then measure the consumption at the maximum brightness. With the AOC Agon Pro AG274QXM and the Cooler Master Tempest GP27U, it is therefore higher than with most other monitors in this overview. It is therefore not surprising that consumption is higher than that of the majority of the competition. The Tempest GP27U consumes almost as much power as Alienware’s much larger ultrawide, while the AG274QXM also requires more power than some 32″ displays.

If we set all screens to the same 150cd/m², the AG274QXM again proves to be more economical than the GP27U. That in itself makes sense, because an LCD with a higher pixel density often has a lower light transmittance, which means that the backlight has to burn harder for the same light output. There are also 4k monitors of this size that are even more economical than the AG274QXM, such as the Gigabyte M28U. Compared to that monitor, the GP27U consumes no less than half as much. The AG274QXM is not an economy champion either. The popular LG UltraGear 27GP850 with the same wqhd resolution and 27″ diagonal requires 12W less for a brightness of 150cd/m² compared to the AOC monitor. That is a difference of 56 percent.


Good HDR monitors are scarce, but with a mini LED backlight it is possible to make an LCD monitor that can show the high contrasts of an HDR image. The first of those screens were very expensive, but now there are options under 1000 euros, in the form of the AOC Agon Pro AG274QXM and the Cooler Master Tempest GP27U. Both provide an HDR image that is clearly better than that of most other monitors.

Although the AG274QXM is much cheaper than the GP27U, the larger housing of this screen has more extras, such as RGB lighting, a remote control for the menu, a logo projector and an included lens hood. Both screens provide four video connections, including USB-C with even enough power delivery for your laptop. The AG274QXM has more USB and audio connections. Judging by the tests we’ve been able to run, you can’t go wrong with either one when it comes to response times. The screens aren’t necessarily much faster than cheaper options, but motion on these screens certainly doesn’t look bad, with a good balance between fast response and limited overshoot. The input lag is also low with both.

Looking at the further test results, it becomes clear that the AG274QXM is a bit more of a first-generation product than the GP27U. That makes sense, because this screen came out a year ago, while the Cooler Master monitor is just new. For example, the backlight of the AG274QXM is controlled in a strange way, with non-switchable pwm dimming that can be disturbing if you are sensitive to it. What I especially find a shame about this screen is the lack of options in the OSD to tailor the display to your wishes. That could have completely eliminated some drawbacks. For example, this screen has an extremely wide color range, which can also be useful for SDR display, but there are no presets to properly adjust the display to AdobeRGB or Display P3.For example, the color deviation in those scenarios increases significantly. The screen does have an sRGB mode. It is a great pity that the brightness is locked in this position, so that it is not very usable. Although the HDR display looks better than on cheaper monitors, the color reproduction and brightness progression deviate considerably from what it should be. Again, that is not something that you can properly remedy using the options in the OSD. Finally, in our test model we see excellent white uniformity combined with very poor black uniformity, but that is a sample-specific property.

Cooler Master has just given the GP27U an extensive OSD, with all the options that I miss with the AG274QXM. For example, in sdr you can achieve a reasonably good display for both sRGB and Display P3 and AdobeRGB. Correct colors are combined with a gray display that could use some improvement. In HDR you also have the choice of various image modes that can be tweaked even further, but that is hardly necessary, because the display is also very good out of the box. Apart from the flickering when you use FreeSync and local dimming at the same time, the inherent limitations of fald and the used ips panel remain as disadvantages. Due to the not so high native contrast of the LCD panel, you often see artifacts such as haloing,where shadows cannot be as pitch black as on an OLED screen or better miniLED screen. The viewing angles of the panel in the GP27U are also very disappointing.

Given the negatives, I’d skip the AG274QXM; while the price is low for a mini led screen, it is relatively expensive for a wqhd gaming monitor, which are already half price in stores. The GP27U is also almost twice as expensive as the cheapest option in the 4k category. This screen offers a good display in many scenarios. It is to be hoped that Cooler Master can still solve the FreeSync problems with a firmware update.

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