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AOC AG251FZ 240Hz FreeSync Monitor Review

Viewing Angles, Uniformity, Response & Lag

Viewing Angles

We all know that viewing angles are TN’s Achilles Heel. The technology will always lag behind IPS and VA. But recent panels have made marginal gains in quality. The red color shift is still there in the horizontal plane, but unlike older designs, the AG251FZ retains dark-level detail much better. Most TN screens will blend the bottom two or three steps, which represent 0, 10, and 20% brightness. From the top, you can see all the steps, but dynamic range is considerably lower than ideal. As long as these monitors remain under 27”, they will be acceptable. But when IPS and VA reach similar speed capabilities, TN’s days will be numbered.

Screen Uniformity

To learn how we measure screen uniformity, please click here.

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Screen uniformity is a sample-specific issue, not something tied to a particular technology. One should not draw a conclusion, based on today’s results, that IPS is inferior in this area. But we’re very impressed at the excellent quality control demonstrated by AU Optronics’ shiny new part, as it takes the top three spots in our black field test. The AG251FZ posts one of the lowest values we’ve ever recorded at 3.47% and 3.75% for the white field measurement. Obviously, this is well below the visible threshold as is the measured color error variation of 1.47dE. It can’t get much better.

Pixel Response & Input Lag

Please click here to read up on our pixel response and input lag testing procedures.

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For those of you who skipped to the end, here’s your reward: the AG251FZ is one of the quickest monitors we’ve ever tested. There isn’t much to report in the response test. Nobody will see a difference between six and seven milliseconds. But input lag is the more important figure, and AOC excels here. This test was performed in FreeSync mode, which means the Low Input Lag feature is disabled. Obviously, the monitor needs its frame buffer to engage adaptive-sync. Clearly, there is no penalty for choosing AMD over Nvidia in this case. Only Asus manages to pass AOC in this metric. If you’re looking for the best possible control response in a FreeSync monitor, you’ve found it.

Gaming With FreeSync

Our AMD-based testbed is still a bit on the slow side with its Radeon R9 285 card, but when playing Tomb Raider on Ultimate detail, we still manage over 65 FPS during the most intense action scenes. Less-demanding sections can hit 80 FPS. Obviously, that’s far below the AG251FZ’s capabilities, but gameplay is satisfying nonetheless. FreeSync is in full operation, and the Medium overdrive setting provides very smooth motion. The best part is the ESP-like control response. You’ll never experience perceivable lag with this display. What we’ve lost in resolution is more than made up for by speed. Even when you’re nowhere near 240 FPS, a monitor like this makes a huge impact.

Booting up Far Cry 4 taught us one thing right off the bat: you don’t want to play below 48 FPS. Even though the AG251FZ supports low framerate compensation (LFC), courtesy of its wide refresh range, we saw an immediate effect on input lag. That processing clearly introduces some control latency. Fortunately, our system played just fine when we dropped the detail level from Ultra to Very High. With framerates over 70, our faith in the monitor was restored—one of the benefits of its FHD resolution. Remember that this game still represents one of the toughest tests of any graphics signal path. Its fine detail is a challenge for all but the most powerful hardware.

Though our system is modest by today’s standards, the AG251FZ showed it is every bit the equal of its G-Sync counterparts. When driven to high speeds, it provides the smoothest gameplay experience we’ve seen, bar none.

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Christian Eberle
Christian Eberle is a Contributing Editor for Tom's Hardware US. He's a veteran reviewer of A/V equipment, specializing in monitors.