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New Easy Free Pursuit Camera: Smartphone. No rail needed.

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New Easy Free Pursuit Camera: Smartphone. No rail needed.

Postby Chief Blur Buster » 30 Dec 2018, 20:09

Easy Pursuit Camera 101
Hand-Waved iPhone/Android Without A Rail

First, let's explain the invention.

A Blur Busters display testing invention by me -- that some of you may be familiar with the Pursuit Camera Instructions. Background info: NOKIA, NIST.gov, and KELTEK researchers have a co-authored conference paper here:

Image

With a rail, one can capture really good pursuit camera photographs like this:

Image

Even though this is much less expensive than commercial equipment -- not all readers can afford a camera rail.

But, in case you didn't know yet.... Display motion blur photography can be done without a rail now, for enduser/amateur purposes.

Now if you see the TestUFO ghosting, you'll see my temporal test pattern invention (the tickmarks that forms a horizontal ladder when eye-tracking the UFOs)


1. Stationary gaze: The sync track is disjointed/broken.
2. Eye-tracking the UFOs: The sync track aligns into what looks like a horizontal ladder.

If you try to photograph it stationary, the photograph is inaccurate for the eye-tracking situation (display motion blur behaves differently while eye tracking, see http://www.testufo.com/eyetracking ... It's the sample-and-hold effect)

Instructions for easy pursuit camera with smartphones. No rail needed:

1. Go to http://www.testufo.com/ghosting
2. Start your camera and then tap-hold the screen to lock your autofocus to close-range (easier to do in stationary text at top of TestUFO)
3. Start recording video with your smartphone
4. Hand-pan the camera sideways a few times, and you'll see the sync track

Just like this video:
phpBB [video]

(You can freezeframe this video and use the , and . hotkeys to single-step to clearest freeze frames.)

Many can do much better than this low-quality video (a random "first try" on an old iPad mini); however, this video demonstrates how much more accurate even a bad pursuit camera (end-user motion blur photographing) can be than a static camera.

You can observe how WYSIWYG the horizontal ladder is -- and ghosting streaks are. This is just an iPad camera at default settings, not even using the "Pro Camera" app that lets you set camera exposure length. Full camera adjustment (exposure, white balance, etc) is preferred for more scientific results. However, in a pinch, this is great for remote troubleshooting -- aka end-user ghosting-artifact troubleshooting.

Image

Image

Certainly, these are not perfect (e.g. smartphone focus issues, shaky hands, etc), but it is a clear demonstration of how a moving camera lens (tracking motion) is a better equivalent of a moving eyeball (tracking camera). Ideal exposure for a pursuit camera is approximately 1/30sec (or four refresh cycles at 120Hz) -- roughly matching human vision integration times -- but there's some leeway for deviations from this, with increasing error margins.

Now you understand pursuit camera! And it's easy to learn.

This can kind of be done with other TestUFO patterns such as http://www.testufo.com/eyetracking and http://www.testufo.com/persistence although without a sync track, it's not as easy to aim the speed of the camera.
But for troubleshooting simple motion blur behaviours (e.g. helping a user), it can still have enough visual data to be useful. Here's an example of 120fps having roughly half the motion blur of 60fps, and 240fps having roughly half the motion blur of 120fps. Exactly as you saw in person. (Note: GtG limitations start limiting differences, as refresh durations get shorter, so faster GtG will amplify differences between 120fps and 240fps).

phpBB [video]


While not as accurate as a rail, it's very clear that that the different framerates have different motion blurs, in an uncannily accurate match to what your human eye saw during eye-tracking.

Further Advanced Reading

For more reading about pursuit camera photography
Want to read more?
- See pursuit camera thread,
- See Display Testers/Reviewers using our pursuit camera technique
- See Full Instructions For Pursuit Camera
- See My Pursuit Camera Paper (peer reviewed) -- I'm the co-author. Co-authored with NOKIA, NIST.gov and KELTEK, and conference paper is on ResearchGate by yours truly Mark Rejhon (Chief Blur Buster).

This test is currently adopted by RTINGS.com, HDTVtest.co.uk, HDTV Poland, TFTCentral.co.uk, and other sites.

But even you, can practice pursuit photography to accurately capture a relatively accurate WYSIWYG approximation of human-perceived display motion blur! Most of them use a rail, but some now do it raillessly and single-step through the frame to find the most accurate freezeframe -- free pursuit camera photography using just your smartphone and your hand!

(If you run a commercial site, and decide to use a pursuit camera -- just remember to credit Blur Busters for the invention and link to us -- and please consider using a rail for improved accuracy. That said, it is indisputable that even hand pursuits can produce more accurate WYSIWYG display motion blur effects than stationary photography.)
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Re: New Easy Method of Pursuit Camera: No rail needed.

Postby Chief Blur Buster » 30 Dec 2018, 20:11

Here's very accurate pursuit camera photography (done earlier by Jorim), as an example, of accurate WYSIWYG photography of ghosting behaviours (different overdrive settings on an Acer XB252Q)

Image

The above 3 photographs (in animated PNG) were captured from a Samsung Galaxy smartphone attached to a smartphone holder on top of a manual sliding camera rail. The colors are a bit oversaturated as is typical of many smartphones, but the tracking accuracy and astounding detail captured of the human-perceived ghosting/corona artifact is par excellencé.
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       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed

Postby Chief Blur Buster » 30 Dec 2018, 20:54

For those unaware, RTINGS made a YouTube video of this technique done more professionally:

phpBB [video]


That's how the professionals do it.

However, you can do it too -- with any smartphone -- and you can do it raillessly with just a hand-waved smartphone! -- and still get useful results! (e.g. comparisions between monitor settings, different displays you own, different refresh rates, etc).
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
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       • List of Ultrawide Monitors
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed

Postby Chief Blur Buster » 04 Feb 2019, 17:08

Techniques To Save Time On Hand-Waved Pursuit Camera
1. Instead of moving your arm, you can keep your arm fixed and pivot your computer chair (with your outstretched arm) instead while pursuiting. Your body doesn't move, only your chair spin. That creates much more stable pursuit camera. It may be a slight arc but the center part of your spin will be parallel to the screen and potentially produce nearly rail-quality pursuits once in a while.
2. Don't begin slowing down your hand pursuit until your hand's already overshot the monitor's right edge.
3. Don't forget to repeat a few times in the same video clip, so don't stop recording video, just move your smartphone back to the beginning at left, keep repeating maybe three, four, five or more times. Until you think you've gotten some good hand pursuits.
4. Excess is your friend here; you're using video as a super-burst-shooting stand-in. 500 pursuit shots means occasionally your hand-wave photo will approach subpixel accuracy. The wonderful invention of the temporal test patterns (the ladder) tells your handwave error margin right away
5. You can single framestep in MPC-HC (Media Player Classic Home Cinema) via Ctrl-Left/Ctrl-Right to find clearest freezeframes
6. You can single framestep in YouTube via comma and period (, and .) to find clearest freezeframes

Fighting Against Smartphone Auto-Everything Behaviours
1. Some smartphones will fight against you with auto-exposure, auto-focus, and auto-whitebalance.
2. If you're using an iOS device, start video recording and first point at a stationary semi-dark area (not too bright and not too dark, not in motion) (e.g. like focussing your camera on the statusbar below the animation) at the distance you need and hold finger down to lock your focus and camera exposure. That will automatically fix the focus/exposure on iOS devices. Now execute your pursuits without touching anything else on your screen.
3. If exposure seems too short (only one or two tickmarks per "ladder rung" in the ladder sync track) or things look too dark, dim your monitor's brightness to force exposure to go longer. If it still doesn't work properly, download a 3rd party camera app such as Pro Cam and manually fix the focus / fix the exposure / fix your ISO / etc -- then the smartphone camera will work with you rather than against you.

Remember, hand-waved pursuit camera is more unscientific than precision propelled camera rails, but it can produce a very excellent approximation of WYSIWYG display motion blur effects during eye-tracking situations! And capture subtle display ghosting behaviours much better than a non-moving camera.
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed

Postby Chief Blur Buster » 02 Aug 2019, 18:02

New article:

LinusTechTips Uses Blur Busters Invention to Take Photos of Display Motion Blur

This is probably one of the simpler Blur Busters explanations of why a pursuit camera is needed -- so check it out!

There are also new instructions to test it yourself with a hand-waved iPhone or Android
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors
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