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Photos: 60Hz versus 120Hz versus LightBoost

post #1 of 2
Thread Starter 
I have done some new pursuit camera tests, since people keep asking (by PM, by email, etc) what the difference is:
Quote:
These photographs compare motion blur during 60Hz vs 120Hz, as well as with the LightBoost strobe backlight enabled. All images below are captured from the same ASUS VG278H computer monitor. These demonstrates differences in perceived motion blur caused by the sample-and-hold effect.

These UFO objects were moving horizontally at 960 pixels per second an ASUS VG278H LCD, moving at a frame rate matching refresh rate, and captured using a pursuit camera using a 1/30second camera exposure (exposing multiple refreshes into the same image).

60 Hz Refresh rate:
Each refresh is displayed continuously for a full 1/60 second (16.7ms)
CROPPED_60Hz-1024x341.jpg

120 Hz Refresh rate:
Each refresh is displayed continuously for a full 1/120 second (8.3ms)
This creates 50% less motion blur.

CROPPED_120Hz-1024x341.jpg

120 Hz LightBoost:
The backlight is strobed briefly, once per refresh, eliminating sample-and-hold.
This has 85% to 92% less motion blur than 60Hz, depending on the LightBoost OSD setting.

CROPPED_LightBoost50-1024x341.jpg

At 120fps@120Hz, a 1/30second camera exposure captures 4 refreshes. All 4 refreshes are stacked on each other, because the pursuit camera is moving in sync with the 120fps@120Hz moving object at a 1/30second camera exposure. The brief backlight flash prevents tracking-based motion blur.

There is extremely little leftover ghosting caused by pixel transitions (virtually invisible to the human eye), since nearly all (>99%+) pixel transition ghosting & overdrive artifacts are kept unseen by the human eye, while the backlight is turned off between refreshes. The backlight strobe flash length, measured to be 1.5ms by TFT Central, is more than 90% shorter than a 60Hz refresh (16.7ms). The LightBoost 10% setting uses 1.5ms strobe flashes, while the LightBoost 100% setting uses 2.4ms strobe flashes. This is still greatly shorter than even a 120Hz refresh (8.3ms)! As a result, motion clarity on a LightBoost monitor is comparable to a CRT display.
post #2 of 2
Thread Starter 
Contrast-enhancement of the final LightBoost photograph, showing ultra-faint remaining pixel transition artifacts that's still seen by human eye. It's almost below the noise floor. Most of the pixel persistence (transitions and overshoots) are hidden during the time period the strobe backlight is turned off, between refreshes.

faint_pixel_persistence-246x300.jpg

Different LightBoost monitors have more trailing artifacts than others (e.g. faint trailing sharp ghost artifacts).

The photos represent the faintness VG278H (Contrast=65%) or XL2411T (Contrast=65%), motion at center of screen. Changing to Contrast=90% makes this much worse; although the picture becomes somewhat more colorful if re-calibrated by a Spyder4 or i1 Pro at the new contrast; so TFTCentral uses a compromise contrast of 75% for VG728HE (the HE is worse than the H). Recovers 80% of color quality, looks much better than out-of-box terrible LightBoost picture. But not good enough for everyone; IPS has better color. So we must still pick our poison.

Not everyone likes LightBoost due to worse color of TN. This dramatic improvement in motion blur is why strobe backlights need to be eventually introduced to 2560x1440p IPS monitors. Get the best of all worlds, without the 120Hz blur (which still not good enough for some of us motion-blur sensitive people).
Edited by mdrejhon - 5/19/13 at 3:06pm
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