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Explaining TestUFO Frame Skipping in layman's terms

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Explaining TestUFO Frame Skipping in layman's terms

Postby Hawk » 24 Jun 2017, 14:32

Hi!

I've had the AOC G2460F for about a year and always had suspicions that it wasn't quite running 144hz, but kinda forgot about it and moved on. It wasn't until my friends started getting 144hz monitors that I was able to see the difference between their monitors and mine and now I'm gonna try and get a replacement.

I tested my monitor using the testufo frame skipping-test following the instructions and setting the exposure of my camera to 1/5th of a second and got this: Image

Before i contact the store I bought it from though, I was just wondering if someone could ELI5 why setting the exposure to 1/5th and taking pictures of black boxes on my screen proves my monitor isn't running at 144hz.

I get the general concept of frameskipping, but I'd like to know what's going on in my particular case.

Cheers! :D
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Re: Frameskipping in layman terms

Postby spacediver » 24 Jun 2017, 14:55

If you set the exposure for 1/5th of a second, that means that the camera sensor is receiving information for 200 ms.

At 144 hz @ 144 fps, each square on the test screen is lit up for about 7 ms (1/144 seconds). With an exposure of 200 ms, around 28 successive white squares should be captured by the camera. If there are no gaps in the image, it means your display didn't skip any frames.
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Re: Frameskipping in layman terms

Postby Hawk » 24 Jun 2017, 15:40

spacediver wrote:If you set the exposure for 1/5th of a second, that means that the camera sensor is receiving information for 200 ms.

At 144 hz @ 144 fps, each square on the test screen is lit up for about 7 ms (1/144 seconds). With an exposure of 200 ms, around 28 successive white squares should be captured by the camera. If there are no gaps in the image, it means your display didn't skip any frames.


Thank you!
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Explaining TestUFO Frame Skipping in layman's terms

Postby Chief Blur Buster » 27 Jun 2017, 15:33

spacediver's explanation is very good.

A long exposure could be 1/10sec or 1/5sec.

It's mathematically slightly easier to explain if the exposure is 1/10sec. That's a camera shutter open one-tenth of one second, so that is one-tenth of 144 refresh cycles. Which equal 14.4 which can be rounded-off to 14 and 15 refresh cycles. That's how many refresh cycles will occur while the camera shutter is open. And that's equal to how many filled boxes should show up contiguously.

Longer exposures create more motion blur (e.g. blurrier sports photos).

Likewise, that "fast-moving" box at http://www.testufo.com/frameskipping gets "motion blurred" into a contiguous blur of 14 or 15 illuminated boxes. (about 1/10th of 144 refresh cycles).

If there's frame skipping, there are gaps in that "motion blur" of that fast-moving box found in TestUFO Frame Skipping

____________

P.S. Many AOC G2460's had had bugs properly running at 144Hz. Many took 144Hz but displayed only 60Hz even when TestUFO successfully says "144Hz" (Which confirms the browser is working correctly). You definitely want to RMA directly with AOC, explaining to them that it is frame skipping, and definitely send them the image too. As far as I know, newer AOC's fixed the problem. It is a well known AOC G2460 firmware bug (a very bad one!) that made many people think it was misadvertising, but newer AOC firmwares have fixed the problem. Be very clear about the frame skipping part, making sure you're talking to someone at AOC who's familiar with the frameskipping bug.
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