[PHOTOS] Accurately Photographing Display Motion Blur: simple pursuit camera setup -- adopted by HDTV reviewer - AVS Forum
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post #1 of 3 Old 05-17-2014, 10:43 PM - Thread Starter
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Here's some excellent motion blur photography utilizing an invention of my own. The pursuit camera invention costs as little as $200 to setup -- just a camera rail & an off-the-shelf camera -- or the only-slightly-more-costly setup photographed below. This is the world's most inexpensive accurate pursuit camera for motion blur measurement, made possible by a pursuit-camera tracking-accuracy-verification temporal test pattern I invented.

Stationary cameras don't accurately capture display motion blur during eye-tracking situations. Thus, pursuit camera tracking of on-screen motion is a vastly far more accurate approximation of eye-tracking of on-screen motion. It makes possible a greater degree of objective comparative display motion blur analysis than stationary camera photography of displays.



RTings' test method, based on my setup, is quite simple. Rather than a UFO (which Blur Busters uses in motion tests), they use an RTings logo graphic scrolling left-to-right at 960 pixels/second (moderately fast motion). The motion itself creates motion blur, which is thus accurately captured by pursuit camera (camera-tracking as an approximate equivalence of eye-tracking). Scientific papers (example: "MPRT pursuit camera" on Google Scholar) have long used the pursuit camera technique scientific measurement of motion blur. However, pursuit cameras were not cheap enough for websites/bloggers to use until a simple invention permitted easy verification of tracking accuracy via a temporal test pattern.

Sony W800B, interpolation disabled

Sony W800B, interpolation enabled

Sony W800B in Motionflow Impulse Mode

Obviously, as you can see there's the LCD GtG pixel transition slowness showing up in the images (the GtG effects is the ghosting / multi-image effect occuring at the left edge behind the motion blurring) that's occuring independently of the persistence-based motion blurring. GtG artifacts is not the same as persistence-based motion blurring. It is already quite obvious, that the persistence-based motion blur out-dominates GtG-based artifacts, at least during the 960 pixels/second motionspeed (representative of fast motion, like sports and videogames) on this display.

The motion blur seen in these captures, is pretty accurately representative of blurring seen in low-blur source material of similar crispness at similar motionspeeds running at framerates matching refreshrates (e.g. fast-camera-shutter sports broadcasts, or playing 60fps video games, or computer use such as 60fps text smooth-scrolling, etc). These motionspeeds are far faster than the typical 6.5ppf used in FPD monoscope and similar tests, so motion blur issues stands out far more, which is important to motion clarity lovers (e.g. CRT, fast plasma, etc), much as video is to videophiles and audio is to audiophiles.

A group of researchers are now about to work on a scientific paper within a year -- writing about my pursuit camera technique (yep -- peer reviewed), so this will be the first real science paper I'm mentioned in, as they were very impressed at what I have done -- my pursuit camera setup cost only $200 to build from scratch -- and outperformed a $50,000 commercial rig.

Related reading:
dsinger, Muza, cinema mad and 5 others like this.

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Mark Rejhon

www.BlurBusters.com

BlurBusters Blog -- Eliminating Motion Blur by 90%+ on LCD for games and computers

Rooting for upcoming low-persistence rolling-scan OLEDs too!

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post #2 of 3 Old 05-18-2014, 01:35 PM
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Very impressive work! Thanks.
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post #3 of 3 Old 05-18-2014, 09:14 PM - Thread Starter
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Thanks for the thumbups!
(including the 5 members that clicked the thumbsup button on my post!)

Here are some additional nifty motion blur photography, that highlights the GtG component of the artifacts -- showing common artifact problems of LCD HDTVs. it is also known that OLED does not have the GtG issues shown below. Plus, we all know that plasma/DLP can avoid the GtG (pixel response) problems that LCDs have. It is noteworthy that most new 120Hz computer gaming monitors do a better job at motion than all the photos on this page. And we see 2013/2014 HDTV manufacturers use new efficient backlight strobing techniques to hide LCD GtG pixel transition slowness in total darkness between strobes on completed refreshes. And all kinds of tricks/techniques going on. But at the bottom line, how does it visually look to the end-user?

A photograph is worth a thousand words, and far more relevant to readers/users than an "1080 lines of motion resolution" FPD test. Without further ado, here are completely intuitive and self-explanatory photographs of very common LED HDTV motion artifacts, found on three different models of LED-backlit LCD HDTVs:

Severe Ghosting
l1400u-motion-blur-small.jpg
Severe ghosting -- This GtG artifacts often looks like this when you have little or no overdrive, and/or when the LCD panel is very cold (cold VA LCDs create much longer ghost trails than when warmed up; the common advice to warm up your display before testing applies to LCDs too). Also, low-quality backlight strobing is occuring with this one, creating severe multi-image effects. (Toshiba L1400U, default)

Inverse Ghosting
h7150-soap-opera-effect-small.jpg
Bright ghosting -- This GtG artifact is called a corona, or inverse ghosting. The ghosting is brighter than the original pixels. This is caused by agressive overdrive (response time acceleration) overshooting its final pixel color value. (Samsung H7150, MCFI=ON)

Inconsistent ghosting
h6350-soap-opera-effect-small.jpg
Inconsistent ghosting -- Look at the corners of the logo. This GtG artifact is caused by inconsistent GtG response speeds. Some pixels are slower than others. The pixels at the upper-left corner and upper-right corner of RTings are transitioning slower, because the pixels have been staying red longer than the pixels in the middle of the logo, where there a lot of white pixels. (Samsung H6350, MCFI=ON)

Conclusion
It is pretty clear that the pursuit camera technique is a wonderful comparative tool that needs to be in more home theater magazines, more reviewer websites, and more display blogs. While not everyone cares about motion blur, there are parts of the audience that cares very much including plasma motion resolution lovers and people who miss CRT motion clarity. In the past, pursuit camera setups were extremely complicated, super expensive ($ in 4 and 5 figures), and hard to do. However, it has become surprisingly easy and inexpensive thanks to the cost-cutting technique (off-the-shelf camera slider rail + favourite off-the-shelf camera or SLR + my temporal test pattern for tracking accuracy verification) that managed lab-quality accuracy without the cost.
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Thanks,
Mark Rejhon

www.BlurBusters.com

BlurBusters Blog -- Eliminating Motion Blur by 90%+ on LCD for games and computers

Rooting for upcoming low-persistence rolling-scan OLEDs too!

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