Confused about Gtg vs MPRT test

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Foulacy
Posts: 2
Joined: 12 May 2021, 13:43

Confused about Gtg vs MPRT test

Post by Foulacy » 12 May 2021, 23:25

Hi there,

I'm confused about one specific test, the GtG vs MPRT test.

TLDR Questions:
-In the test explanation, what is meant by "observe the edge sharpness"? Does it refer to the horizontal line that exists where the two panels meet? Or is it referring to the vertical lines on the edges of each panel as they move through space?

The reason I ask is because if it's referring to the horizontal line where the two panels meet, then I'm wondering if it's better to have more sharpness between the two bars, or a more blurred, less sharp line? My confusion is explained below.

On the testing page it says:

"Observe the edge sharpness difference between the top and bottom halves of the moving bar! Fast pixel transitions will amplify the edge-sharpness difference between the top and bottom half. Slow pixel transitions will reduce the difference between top and bottom."

-This would lead me to believe that more sharpness is better, because it would indicate faster pixel transitions, which I also assume that is what we want.

However on the GtG vs MPRT FAQ it says:

"There is a bigger clarity difference in the moving edges between top/bottom halves when the GtG-vs-MPRT ratio is much bigger. Try this animation on a TN or OLED display which often has <1ms GtG but 16.7ms MPRT!"

So then I'm thinking, wouldn't it be best to have as low of an MPRT as possible? Meaning the edge difference would be as non-existent as possible.

Please let me know if I can help explain my confusion further, thank you for your time!

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Chief Blur Buster
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Re: Confused about Gtg vs MPRT test

Post by Chief Blur Buster » 14 May 2021, 15:59

Foulacy wrote:
12 May 2021, 23:25
Hi there,

I'm confused about one specific test, the GtG vs MPRT test.

TLDR Questions:
-In the test explanation, what is meant by "observe the edge sharpness"? Does it refer to the horizontal line that exists where the two panels meet? Or is it referring to the vertical lines on the edges of each panel as they move through space?

The reason I ask is because if it's referring to the horizontal line where the two panels meet, then I'm wondering if it's better to have more sharpness between the two bars, or a more blurred, less sharp line? My confusion is explained below.

On the testing page it says:

"Observe the edge sharpness difference between the top and bottom halves of the moving bar! Fast pixel transitions will amplify the edge-sharpness difference between the top and bottom half. Slow pixel transitions will reduce the difference between top and bottom."

-This would lead me to believe that more sharpness is better, because it would indicate faster pixel transitions, which I also assume that is what we want.

However on the GtG vs MPRT FAQ it says:

"There is a bigger clarity difference in the moving edges between top/bottom halves when the GtG-vs-MPRT ratio is much bigger. Try this animation on a TN or OLED display which often has <1ms GtG but 16.7ms MPRT!"

So then I'm thinking, wouldn't it be best to have as low of an MPRT as possible? Meaning the edge difference would be as non-existent as possible.

Please let me know if I can help explain my confusion further, thank you for your time!
MPRT(100%) is equal to frame visibility time.

Thus, on a non-strobed display (sample-and-hold), MPRT(100%) can never be less than refresh cycle duration.

But as GtG gets faster and faster, that means a bigger difference between GtG (because it decreases) and MPRT (cant decrease).

So on a fast-GtG sample-and-hold display, the clarity difference of top/bottom is bigger.

For very slow GtG displays (like old 33ms 60Hz LCDs), the difference between top/bottom can become almost non-existent.

In the same FAQ, GtG versus MPRT is this guaranteed minimum MPRT(100%) number:

Image

So at 60Hz, you can never have an MPRT(100%) of less than 16.7ms.
And you can never have an MPRT(10%->90%) of less than (0.8th/16.7)ms
But GtG can keep improving until GtG equals 0.

Even at GtG=0, there is still MPRT motion blur from the sample-and-hold effect.

Thus, GtG-vs-MPRT test will have amplified differences (between top/bottom halves) when GtG is vastly faster than MPRT.

Do you understand better now?
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