AOC AGON AG251FG review: the best 240Hz monitor yet

Monitors and Projectors, Reviews

The AG251FG may come with the same 24.5-inch 240Hz panel as the Viewsonic XG2530 and BenQ XL2540, but it adds something new in the form of G-Sync. Let’s see which monitor reigns as our favourite by the end of the article.

We’ll start with a brief look at the monitor’s design and features.



The AG251FG is immediately recognisable as an AOC monitor, with the company’s trademark straight-edge aluminium stand. The stand rests on a V-shaped base, just wide enough to fit a tenkeyless (compact) keyboard between the two legs.

The AG251FG’s bezels are reasonably thin (2.5mm) on the top and both sides, and a little chunkier towards the bottom. There’s an AG251FG label in the upper right and an AGON wordmark in the bottom centre; otherwise the monitor is unadorned.

The stand offers a good range of adjustment, including 130 millimetres of height adjustment. Once your desired height is found, you can easily mark this measurement on the scale provided for faster setup next time.

The underside of the monitor is also V-shaped, with the HDMI and DisplayPort inputs on the left…

…and two USB 3.0 ports, a USB 3.0 upstream (Type B) port and a circular power connector on the right.

You’ll find two more USB 3.0 ports on the right side of the monitor, just beneath two 3.5mm headphone inputs.

There’s a headphone jack on the rear, which can be rotated in and out as required.

Buttons to control the on-screen display are found under the right side of the monitor, with white labels visible from the front. There’s also a white power LED here.

The back of the monitor includes a 100×100 VESA mount, if you’d like to replace the mount or wall-mount the monitor.

That just about covers the design of the monitor, so let’s take a moment now to begin our benchmarks. Later, we’ll share our first-hand impressions to evaluate the monitor’s suitability for gaming and other tasks.



In order to provide a suitable test of this monitor’s capabilities, we used an i1 DisplayPro colourimeter for testing brightness, contrast and luminance uniformity. In terms of software, we’re relying on the open-source DisplayCal 3.4 and the i1Profiler that comes with our new colourimeter. Let’s get started!

This is the first time we’re using the i1 DisplayPro, i1Profiler and DisplayCal, so we welcome your feedback on the format of these results.



As usual, before we perform the benchmarks we’ll be calibrating the monitor as closely as possible to our standard measurements: 120 nits brightness (38 / 100), gamma 2.2 and a white point of 6500K. User colour settings were 48 (R), 51 (G) and 50 (B).

ICM file

Here’s the .ICC / .ICM file produced by the DisplayCal software we’re using, if you want to use it yourself. The usual disclaimers apply; panels vary and this may not produce a superior result:

Gamut coverage

We measured 93.7% coverage of the sRGB gamut, a reasonable result for a TN panel, and 101.3% volume (i.e. the monitor displays some colours outside of the sRGB colour space). For other colour spaces, we hit 68% of AdobeRGB coverage and 71.7% of DCI P3 coverage.

Contrast & White point

Contrast ratio was measured at 753:1 after calibration in the user colour mode. TN panels don’t tend to boast the best contrast, but more than 750:1 at 120 nits should be more than sufficient for our purposes. In other colour modes, the contrast ratio was higher, generally between 890:1 and 950:1, coming close to the claimed 1000:1 contrast ratio.

The white point ΔE is 0.28, showing we’re almost dead onto our desired figure of 6500K. Awesome.

Colour accuracy

We tested the monitor against the ColorChecker 24 Patch reference in i1Profiler. Using the ΔE 1976 metric, the monitor has scored excellently. For the 24 patches we checked, the AG251FG gets an average ΔE of 1.20 — really good. By comparison, the two other 24.5-inch 240Hz monitors we’ve tested got values of 1.40 and 1.50, making the AOC monitor our best performer yet.

If we take a closer look at the problematic swatches, you can see that the lowest 90% ΔE values averaged just 0.78, while the highest 10% ΔE averaged 5.83. You can see that our old friend, teal, is the real outlier with a 9.07ΔE value — everything else was good to excellent. Overall, a nice result!

Screen uniformity

DisplayCal includes a rather more comprehensive uniformity measuring tool than the Spyder software I was using earlier — instead of being forced to use a 3×3 grid, you can use 5×5, 7×7 or even 9×9.

Here are the 5×5 grid results, showing that the monitor has no notable issues in terms of colour or luminance uniformity. The left fifth of the screen was the only area that showed a noticeable variation, with lower brightness levels (105 nits vs around 120 nits) and higher ΔE values (2~3 vs 0~2).

You can click the image below to read the results in full if you wish.

Overall, the monitor has a strong performance in our tests, with adequate contrast, excellent colour accuracy and great uniformity as well. The TN panel isn’t quite capable of covering the entire sRGB space, but for a monitor not intended for professional use this isn’t an issue.



Here are our first-hand impressions after using the AOC monitor for a three week review period, including both gaming, watching TV and getting stuff done.


Unsurprisingly, 240Hz monitors provide a gorgeously smooth and responsive experience in games. That makes it easier to track moving targets in shooters, or react to debris appearing on the track of a racing game. Once you’ve gotten used to the fluidity of a 240Hz display, it’s hard to go back — even to 144Hz. The jump isn’t as noticeable as 60 to 144Hz, but it’s definitely there. If you want to maximise your competitive advantage in games like OverwatchCounter-Strike or League of Legends, 240Hz is where you want to be.

The 1080p resolution is an achievable target for most gaming PCs that are mid-range and above, including most gaming laptops as well. That means you should be able to hit 200+ fps in older games, and a playable 60 fps in newer titles at higher graphic fidelity settings. The 25-inch screen doesn’t look noticeably grainy at this resolution either, which is something I can’t say for 27-inch monitors.

The inclusion of G-Sync (see comment below) is a nice safety net for more recent and system-intensive games, e.g. Prey, PlayerUnknown’s Battlegrounds or Forza Motorsport 7. It helps to ensure that these games run smoothly without tearing at lower fps counts.

All in all, it’s a sensible design spec that should appeal to players of fast-paced, competitive video games. If you prefer slower-paced titles, then your money would be better spent on an IPS monitor that runs at a lower refresh rate and/or a higher resolution.

Work & Media

Outside of games, the 240Hz refresh rate makes for a silky smooth experience — whether you’re navigating through your hard drive, editing a document or surfing the web. Even silly loading screen animations are worth marvelling at. The high refresh rate makes your computer feel noticeably faster, and even if it doesn’t lead to an increase in productivity, it’s still a nice feeling.

Elsewhere, the AG251FG is a mixed bag. The TN panel is relatively well calibrated and has decent viewing angles, but colour accuracy isn’t on par with productivity-oriented IPS displays. Similarly, photos and videos don’t ‘pop’ quite as much they do on OLED displays, and you’ll probably prefer to watch shows or movies on your HDTV.

Still, this AOC monitor is far better for watching TV than a cheap office monitor or a mid-range laptop, so at least you won’t be scrambling to get it off your desk whenever you want to watch your favourite show.

The 1080p resolution is a little limiting when it comes to multi-tasking, and generally we’d recommend a 1440p or higher monitor for productivity (or just multiple monitors). Still, we wrote the bulk of the review of this monitor without issue, including a bit of image editing in Photoshop.


Comment: Is G-Sync worth it?

The most unique part of the AG251FG is the inclusion of G-Sync. This normally adds at least £50 to a monitor’s price, and indeed the AG251FG at £470 is more expensive than the G-Sync-destitute ViewSonic XG2530 (£450) and BenQ XL2540 (£400). Indeed, the Dell Alienware AW2518 has 240Hz and costs just £330. So — is G-Sync worth it?

In my eyes, it’s not worth it; G-Sync just doesn’t make sense on a 240Hz monitor. Let me explain.

G-Sync is designed to give you a consistently smooth experience and reduce tearing, at the expense of a little input lag. That is great for intensive games, as you can have your FPS count drop from 60 to 30 or 45 frames per second without the game becoming noticeably more unresponsive. For modern titles, underpowered computers or both, G-Sync can be a godsend.

However, if your computer is capable of hitting in excess of 144 frames per second, the limit of many gaming monitors, and therefore you want a 240Hz monitor, then G-Sync won’t do much for you. With hundreds of frames per second, your FPS can oscillate substantially without it becoming noticeable, even with G-Sync disabled. Enabling G-Sync adds that extra bit of input lag as before, but you don’t really gain enough to make it worthwhile.

The long and short of it is this: in the sorts of games that you would want to play at 240Hz — like Counter-Strike, DotA 2 or Overwatch — it’s almost always better to minimise your input lag by disabling G-Sync and other v-sync modes entirely.

The only place that having G-Sync on the AG251FG makes sense is for games like PlayerUnknown’s Battlegrounds, which are played (somewhat) competitively but FPS counts remain low, perhaps around 100 fps, even on well-equipped computers. You could perhaps make the argument that G-Sync would lead to a more consistent experience here, but then why not just get a 144Hz monitor and save some cash?

The only real perfect use case is for gamers that want to play both older (CS:GO) and newer (PUBG) competitive games, allowing you to have the best possible refresh rate in older games and G-Sync in newer and more demanding titles. I can see some logic in that, but I wonder how much of the population that describes!


Wrapping up

The AG251FG is a tantalising prospect, providing the best out-and-out performance we’ve seen on a 240Hz monitor so far. While 27-inch 240Hz monitors are on the horizon, the AGON provides a winning combination of fluid gameplay, great adjustability and stellar looks that should make it a strong choice for years to come.

Buy the AGON AG251FG on Amazon

Last modified: January 11, 2018

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