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

Many sites including LinusTechTips, RTINGS, TomsHardware, and others use the free Blur Busters pursuit camera invention. Now also avaialble as a rail-less smartphone wave, too!
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New Easy Free Pursuit Camera: Smartphone. No rail needed.

Post by 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 ww.testufo.com/eyetracking ... It's the sample-and-hold effect)

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

1. Go to www.testufo.com/ghosting and put it in full screen mode.
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 www.testufo.com/eyetracking and 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.

Post by 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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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed

Post by 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).
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed

Post by 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.

Better yet, purchase/download a "Pro" camera app (there are many on the app stores) with SLR-like adjustment features that also works for video too. Video pursuit camera with SLR-like adjustments, becomes the world's easiest pursuit camera.
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed

Post by 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
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed.

Post by Chief Blur Buster » 16 Mar 2020, 17:01

Two reviewers are making mistakes by violating test guidelines that cause me to be unable to trust the integrity of the pursuit camera photography, because the tickmarks are the evidence of scientific accuracy.

When photographing www.testufo.com/ghosting or other pursuit-camera compatible test pattern,
Please Follow Guidelines
Please Confirm Scientific Integrity

Image

Image

Image

Image

[!] CRITICALLY IMPORTANT FOR TRUST [!]: Just because photo (or individual video frame) looks correct despite bad tickmarks, doesn't mean the photo can be trusted. The tickmarks is the trust. The tickmarks is hardcoded evidence of pursuit camera accuracy. Please help us trust the photograph by showing accurate tickmarks, please. Camera exposure must be at least 2x refresh cycle length minimum (and preferably about 4x refresh cycle), to represent aggregate human vision integration time accurately. Example: For 120Hz refresh rate -- that means 1/30sec camera exposure for photographs -- or 1/30sec exposure per video frame if doing video. For end users doing the easy rail-less method via smartphone hand-wave, try to get less than 1 pixelwidth error margin. For professional reviewers, try to get less than 0.2 pixelwidth error margin, if you can!

Pursuit Camera Instructions

For those wondering how to use a pursuit camera for free:
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed.

Post by Chief Blur Buster » 01 Apr 2020, 00:19

Here are improved instructions that works with many "Professional Camera" apps in Google Play and iPhone App Store. Such as "DSLRCamera" on iPhone.

Setting Up Your Smartphone For Easy Hand-Wave Video Pursuit Camera

1. Go to Google Play or iTunes on your smartphone
2. Download and install a high-rated professional SLR-like Camera App that allows you to do manual-everything during video
3. Run www.testufo.com/ghosting
3. Configure video camera app to FIXED EXPOSURE (Prefer 4 refresh cycles, i.e. 1/30sec 30fps for 120Hz)
4. Configure video camera app to FIXED COLOR TEMPERATURE (6500K)
5. Configure video camera app to FIXED FOCUS (with phone arm's length away from monitor)
6. Finally, configure video camera app to a BRIGHTNESS or ISO SETTING that doesn't underexpose/overexpose per frame.
(Note: Framerate doesn't matter as much as ability to adjust camera exposure per frame, you may have to configure the camera frame rate in order for it to let you adjust the exposure settings the way you want it. Also, not all camera video recording apps lets you configure everything, so you may have to experiment with different apps until the app lets you correctly configure the video settings).
7. Start video recording.
8. Hand wave the video a few times just like the YouTube video embed, from about arm's length away
9. If you need more steadiness, try stiffening your arm and swivel your computer chair instead
10. Afterwards, play the video using a good single-frame-stepping player app (if using smartphone, use a video player app that has a touchscreen jog slider, combined with PREV/NEXT framestep buttons) to find the clearest freezeframe.
11. You've found your good smartphone hand-pursuit photo (simply buy using video as an equivalent of photo-burst-shooting to maximize odds of a good pursuit photograph). Save the freeze frame as a photo. This becomes your good pursuit photo.
12. Done!

(The video file can be kept, it can be quite educational showing people how a pursuit camera works -- the video file shows self explanatory behaviours -- it instantly tells the users that camera tracking is the same thing as eye tracking -- where tickmarks looks bad until the camera goes at the same speed as the UFOs -- just as if you did WYSIWYG).
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed.

Post by Chief Blur Buster » 07 Apr 2020, 14:41

Hand Wave Pursuit Camera With Projectors
Sometimes a projector needs to have a pursuit camera. Follow the same instructions above, except with these modifications:
-- Stand from projector screen approximately one screenwidth away.
-- Don't be too close to the projector screen!
-- Hold smartphone with stiff arm (don't move arms or shoulders). You can even hold smartphone with both arms if it feels more stable.
-- Rotate yourself with your waist instead

Important Note For Color-Sequential Projectors Such As DLP
With DLP projectors, It's more critical to keep camera exposures an exact multiple of refresh cycles. For example 1/60sec camera exposure for a 240Hz projector, or 1/30sec camera exposure for 120Hz projector. It's OK to use 1/30sec for 60Hz (2 tickmarks), since that's easier than 1/15sec (4 tickmarks). Exact integer multiple is important because of temporal color (i.e. DLP color wheel) and you must average this out properly. Divergences will add color tintings/artifacts to pursuit camera images, especially when very few refresh cycles are exposed. To get WYSIWYG photos, you will need to use an integer multiple of refresh cycles. Also, some projectors will spread temporal color over multiple refresh cycles, so you may need to increase refresh-cycle stacking beyond 4 -- some projectors may require stacking 6 refresh cycles (e.g. 1/20sec for 120Hz), depending on how they spread temporal color over multiple refresh cycles.

Exposure length exactness will compensate for lack of exposure sync with refresh cycle beginnings: It will compensate for the fact that shutters are not aligned with refresh cycles (fortunately, that's not necessary for Blur Busters pursuit camera invention). All DLP projectors I've seen will have color-sequence-repeats every 1/30sec and 1/60sec, so those exposure lenghts are pretty safe even with unsynchronized shutter. The human eye does not synchronize to DLP either, but the eye is continuous rather than a single photo. So shutter-length constraint is chosen as a compromise between WYSIWYG accuracy and ease of getting WYSIWG -- it becomes almost perfect when exposing 4 refresh cycles on nearly all displays -- but some DLPs may actually odd counts of refresh cycles (camera shutter length equalling 3 or 6 refresh cycles) to maximize the WYSIWG look without going to unsustainably long camera exposures (e.g. 1 second).
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed.

Post by Chief Blur Buster » 11 May 2020, 12:13

Also,

A related must-read thread:

Are Hand-Wave Pursuit Camera Silly/Stupid?
(Long post, with useful analysis information and caveats about smartphone limitations such as compression artifacts)

TL;DR: No. Hand-waves are still scientifically usable!

Amazingly, some expert handwaves actually exceeded some low-end camera rails. The sheer number of scientific samples (thousands of "photos" in a single video file) creates random chance moments of 1-frame near-perfect tracking accuracy within error margins of rail vibrations/stiffness. So the scientific accuracy venn diagram overlaps. And we've had successful analysis executed on hand-wave pursuits, thanks to improving hand-wave techniques (since it's a zero-cost pursuit camera for low-budget research). The sync track is pratically almost a certificate of tracking accuracy.
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Re: New Easy Free Pursuit Camera: Smartphone. No rail needed.

Post by 1000WATT » 11 May 2020, 12:36

Keep in mind. Sometimes people around you (relatives, friends, girlfriends) may react strangely to your attempts to photograph the monitor. When my wife asked: what are you doing? There was clearly concern in her voice. Most likely she was worried about my mental health. I replied: any UFO should be shot with shaking hands at the worst camera. This somewhat relaxed the situation.
I often do not clearly state my thoughts. google translate is far from perfect. And in addition to the translator, I myself am mistaken. Do not take me seriously.

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