Discussion about Display Motion Physics (BFI, Color Mixing, Video Issues, Etc)

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Discussion about Display Motion Physics (BFI, Color Mixing, Video Issues, Etc)

Post by Chief Blur Buster » 30 May 2020, 20:49

Thread split from Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)
Chief Blur Buster wrote:
30 May 2020, 20:49
The Classic Double Image Effect: CRT 30fps at 60Hz

[This thread is interesting only to people who are familiar with CRTs and plasmas and the 30fps double-image effect]

Remember the CRT 30fps at 60Hz effect? I've reproduced it in software-based BFI with a new custom easter egg TestUFO modification.

TestUFO Animation: Software-Based Double Image BFI Demo

(Look at the 2nd UFO for a double image effect similar to CRT 30fps at 60Hz)
Click on this to watch this full screen:


Best performance occurs with a desktop browser that is correctly running at framerate=refreshrate. Observe the 2nd UFO. It has a duplicate image, similar to CRT 30fps at 60Hz.

To emulate is correctly via software-based BFI required me to run at 1/4 frame rate. Right now, the animation is emulating a half-refresh-rate CRT, and you need half-framerate to get double images, so it requires quarter-frame rate (combined). So 15fps on 60Hz, for a software emulation of the double-image effect.

For impulsed displays, this is normally how things look:

Image

This happens at all refresh rates. We already know it also occurs at 60fps at 120Hz strobed (ULMB, ELMB, LightBoost, etc). Even 120fps on a 240Hz impulsed/strobed display still show double images. And 60fps at 240Hz impulsed has quadruple images.

Assuming your browser runs it well, this works on all ordinary non-strobed LCDs / OLEDs.
- Runs 15fps on 60Hz LCDs
- Runs 30fps on 120Hz LCDs (best emulation of CRT 30fps at 60Hz)
- Runs 60fps on 240Hz LCDs

If you have a higher-Hz display, these below links look MUCH better to demo:
TestUFO BFI Double-Images For 120Hz+
TestUFO BFI Double-Images For 240Hz+

As far as I know, this is now the world's first software-based demo of the equivalent of a CRT [email protected] double-image effect, as long as your browser can run framerate=Hz.

How did we make it work?

It's a 4-frame software-based 2-repeat sequence of 1 visible, 1 black frame, using a cadence of 100%,0%,100%,0% (of the same static frame) per 1/15sec on a 60Hz monitor. That generates a software-based double-image effect on nearly all display technologies (LCD, OLED, DLP, etc). The motion of human eye-tracking is actually the main cause of LCD motion blur, clearly demonstrated in animation demo http://www.testufo.com/eyetracking ...GtG pixel response is NOT the main cause anymore, it's static pixel visibility time from sample-and-hold. Common LCD motion blur is mathematically directly proportional to pixel visibility time (excluding GtG time), as explained in Blur Busters Law: The Amazing Journey To Future 1000Hz Displays as well as Pixel Response FAQ: GtG versus MPRT.

Fundamentally, all common impulse-based technologies are essentially a form of per-pixel BFI. CRT phosphor dot, for example, it illuminates nearly instantly and then fades after with phosphor decay.

Simplified Motion Blur Mathematics

For the purposes of this post, terminologically we will treat BFI and CRT impulse scanning as an overlapping venn diagram. CRT is terminologically a "phosphor-trailed rolling-scan BFI" as BFI doesn't need to be engineered as full frames, or even a 50%:50% refresh-cycle-granularity BFI. Normally we don't call CRT as BFI, because it's a natural inclusion. But we will, for the purposes of this post (from a human vision perspective), treat CRT a BFI behaviour that is essentially defacto 1%:99% ON:OFF per-pixel-based BFI. This depends on how slow/fast the CRT phosphor is, but you get the idea, brief pixel flash, lots of black time.

Go play with BFI with the settings at the top of the Software BFI demo. BFI and CRT venn diagram overlaps. Think of LCD computer refresh cycles as refresh-granularity persistence. 240Hz displays are like phosphor persistence in 4.2 millisecond increments. Very educational to learn!

Here are some great more BFI demos:
TestUFO Animation: Variable BFI -- Demos variable amounts of blur against full-frame-rate
TestUFO Animation: Double Images -- Demos double image effect
TestUFO Animation: Triple Images -- Demos triple image effect (test at 120Hz+, flickers much 60Hz)
TestUFO Animation: Blue Frame Insertion -- Demos that blank frames don't need to be black

NOTE: For best TestUFO animation performances, make sure to run this in a browser capable of running framerate=Hz, though multimonitor sometimes interferes. To minimize stutters during this demo on some computers, you may need to close all tabs and run only on primary monitor. May need to test a different browser, FireFox vs Chrome.

For more reading about display behaviours, see Blur Busters Law: The Amazing Journey To Future 1000Hz Displays.
Thread split from Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)
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Discussion about Display Motion Physics (BFI, Color Mixing, Video Issues, Etc)

Post by mynm » 06 Nov 2021, 15:38

Hi, this in a very interesting theread thanks for creating it and the emulation.

But I have a question that I don't see is answered here. What is the technical explanation of this double image effect?.

I have recorded the normal compare framerate test at 60 fps, and what I see with a video editor, is that what is doing is to change the ufo possition once a frame at the 60 fps lines, every two frames frames at the 30 fps line and every three frames at the 15 fps line. The effect seems to display the initial and final position of the ufo when its possition don't change and additionals in between images. So it seems is an intended effect for not to see stuttering, I guess. So I suppose is not and optical effect. Am I right?.

I have tested the normal compare framerate test with a CRT and what I see is that for example at 50 hz and 50 fps I don't see a double image, but at 100Hz the 50fps line the ufo is doubled, so is not a framerate problem.

It will be great to get a response here as at the forums I have talk about this or I have researched for to get and answer, it's that you are drunk or you have a visual problem :lol: .
Last edited by mynm on 07 Nov 2021, 13:20, edited 1 time in total.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by thatoneguy » 07 Nov 2021, 02:36

Think of 1hz = 1 frame.
[email protected] would be showing each frame twice.
This effect is more noticeable on low persistence displays compared to sample-and-hold ones.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 07 Nov 2021, 15:05

thatoneguy wrote:
07 Nov 2021, 02:36
Thanks for the response, yes [email protected] shows each frame twice, but 50 fps at 50hz is not. The thing is that I don't know what is doing that effect, as I understand at [email protected] the repeated frame should be a stutter. That is what I see editing videos, I had problems with some stutter I see in some video and what I see with the editor is that when the frame is repeated the video stutters. So in the ufo test as each frame is repeated twice at the same position it should stutter.

But as I said the effect seems to display the initial and final position of the ufo when its possition don't change and additionals in between images. So what I suppose is that it seems an intended effect for not to see stuttering.

I have edited some videos to see if it's repeating the image or doing what I said. To see if the initial and final position is shown at the same time I have changed the color of the ufo per frame to red and green. And what I see is that for 60fps and 60hz is that like you can se see in this video:

- For 60 fps, the image is not doubled but the color of the ufo is melted, and is doing this at the CRT and at the LCD.

- For 30 fps, the image is doubled the right and the left side is of a different color and the color of the center is melted, and is doing this at the CRT and at the LCD.

- For 15 fps, the image is tripled whit the colors as above, and is doing this at the CRT and at the LCD.

I also have tested and black frame insertion like video covering the repeated frame at the 30 fps line. And what I see like you can see in this video is that the ufo at 30fps is not doubled and its color is darker, maybe because the background is black and is melting the color. This happens at the CRT and at the LCD. So the 30 fps is not the cause of the doubled image at 60hz.

And I have gone further, I have recorded the ufo test at 30hz and changed the ufo color in each frame as above. I have tested the video in a LCD at 30hz. And what I see like you can see in this video is that the 30 fps line is like the 30 fps line at 60hz.

Finally I have done the black frame insertion like video at 30hz at the 30 fps line. And what I see at like you can see in this video is that the ufo is doubled but only with one of the color and that the right ufo is darker as I said maybe because the background is black. So is doing the same as 30 fps with the repeated frame at 60hz despite there are 15 fps.

About that the right ufo color is darker at 30 fps and 60 hz, it don't occur at the CRT. Maybe is becaue of the low respones time of the LCD and maybe is the cause that this effect is more noticeable on low persistence displays compared to sample-and-hold ones. I will have to see if changing the background color from black to white the color is brighter.

To end I have to say that I have also tested an LCD TV at 120HZ and I see whit the frame drop test that is dropping half of the frames. It shows 120 hz at the ufo test but it looks like 60 and whitout flickering and vsync was OK. So I do not trust the hz I see at windows maybe it is 60 hz maybe the 30 hz resolution that I have tested is also 60 hz with repeated frames, I can know.

I don't know how to explain all this thing technically, will be great to have and explanation for some one here.
Last edited by mynm on 09 Nov 2021, 06:38, edited 2 times in total.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 08 Nov 2021, 11:15

I have done more test. First I have done the blak frame like test to the 30 fps line but with the stars background and the image is not doubled but the ufo color is darker at the CRT and at the LCD. You can see it in this video.

The second test is to see if a white backgraund color affects at the first ufo at the 30 fps line more for the LCD than for the CRT as it seems that the black one seems to do the first ufo more darker. To do at I only have inverted the video colors. And what I se is that, is not clear, maye a little. At the CRT it seem more clear that right and left part of the two merged frames are brighter than the center, but with no diference of color. You can see it in this video.

The last test is a white frame insertion like test at the 30 fps line. The result is the same as at the black frame tested above. You can see the video here. But I have noticed more things about the frame insertion like test, the 30 fps letters don't disappear it is onli more bright or dark. If you go frame per frame it is covered with the white or black image I have put to cover the repeated ufo.

The conclusion I see about this is that as colors are merged between frames and can't be seen separately. It seems like at 60 fps and 60 Hz is like seen only 30 efective fps. It happens at the LCD and at the CRT, so it seems is not a response time problem. Again I don't know how to explain technically why is this happening :?: .
Last edited by mynm on 09 Nov 2021, 06:41, edited 2 times in total.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 08 Nov 2021, 13:44

mynm wrote:
06 Nov 2021, 15:38
Hi, this in a very interesting theread thanks for creating it and the emulation.

But I have a question that I don't see is answered here. What is the technical explanation of this double image effect?.

I have recorded the normal compare framerate test at 60 fps, and what I see with a video editor, is that what is doing is to change the ufo possition once a frame at the 60 fps lines, every two frames frames at the 30 fps line and every three frames at the 15 fps line. The effect seems to display the initial and final position of the ufo when its possition don't change and additionals in between images. So it seems is an intended effect for not to see stuttering, I guess. So I suppose is not and optical effect. Am I right?.

I have tested the normal compare framerate test with a CRT and what I see is that for example at 50 hz and 50 fps I don't see a double image, but at 100Hz the 50fps line the ufo is doubled, so is not a framerate problem.

It will be great to get a response here as at the forums I have talk about this or I have researched for to get and answer, it's that you are drunk or you have a visual problem :lol: .
CRT includes natural flicker so you still get double images at lower than native CRT Hz.

With LCD, you have to intentionally add flicker by using a lower "emulated Hz". 30fps BFI single strobe = emulation of 30Hz CRT via software-based BFI. This becomes the "real CRT style refresh rate".

Now halve the frame rate of the CRT style single strobed refresh rate (e.g. native CRT rate, or halved software BFI'd LCD refresh rate), you get double images at:
- Half CRT frame rate
- Quarter frame rate on LCD (halved by software BFI to create the emulated CRT, then half the emulated CRT flickered refresh rate)

You have to think of the number of flashes per second, not the actual native refresh rate.

The only way to add flashing to a sample-and-hold display is to virtualize a simulated refresh rate over a longer sequence of actual sample-and-hold refresh rate.

Software BFI always emulates a lower-Hz. Thus, the highest frame rate to emulate a double image effect on an sample-and-hold LCD (non-strobed) is quarter the frame rate, because you first have to halve the refresh rate to virtualize a emulated CRT.

So basically, a 120Hz sample-and-hold LCD (without hardware-based backlight strobing) at the highest possible Hz, can only emulate a 60Hz CRT via software based black frame insertion. Lowering persistence (percentages of refresh cycle illuminated) requires even lower, e.g. 60fps at 240Hz can be 1/4th persistence.

For more information about Blur Busters Law, please study Blur Buters Research at www.blurbusters.com/area51
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 08 Nov 2021, 15:09

Chief Blur Buster wrote:
08 Nov 2021, 13:44
Thanks for the response and the explanation. I think I understan what you are saying I will review and think about it. I understand that I had done what you say adding a black or white patch to cover the repeated image at the 30 fps line at 60 Hz.
Chief Blur Buster wrote:
08 Nov 2021, 13:44

CRT includes natural flicker so you still get double images at lower than native CRT Hz.
I don't see that I see a none doubled image at 45hz or 50hz with my current CRT and I had tested this whit another two ones years ago.

I have done another two video tests.

The first one is at 60 Hz and 60 fps, adding a half white path at the right of the ufo in one frame and at the left in the next frame. And what I get is more or less one ufo but the white mixed to its color. I see the same at the CRT and the LCD. You can see the video here.

And the seconf is to do the same to the 30 fps line and covering the repeated image. And I get the same and despite there are only 30 positions/fps for the image. You can see the video here. Edited: it seems that I have chose a wrong video it is not covering the repeated frame, but it looks as it is. I will upload the correct video. This is the correct video.

So what it seems is that at 60 Hz the effective framerate is 30 fps, as it seems to mix two images to get one that is dysplayed, and that even with 15 fps it looks the same.

Again, I don't understand and don't know how to explain this technically.
Last edited by mynm on 10 Nov 2021, 07:43, edited 5 times in total.

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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 08 Nov 2021, 16:11

mynm wrote:
08 Nov 2021, 15:09
I don't see that I see a none doubled image at 45hz or 50hz with my current CRT and I had tested this whit another two ones years ago.
Please refer to this diagram:

Image
Hz = flicker Hz (not necessarily refresh rate Hz)

One flash per static frame = one image (when tracking eyes)

Two flash of the same identical static frame = double images (when tracking eyes)

etc.

If you're testing CRT at 50Hz, please test 25fps.
If you're testing CRT at 45Hz, please test 22.5fps.

TestUFO double image animation creates the double image effect in pure software via this:
Sequence 1 of 4 = flash a frame
Sequence 2 of 4 = black frame
Sequence 3 of 4 = flash the same unchanged frame as sequence 1
Sequence 4 of 4 = black frame

Your eyes are analog and following the UFO in its vector. Your eyes are in a different position in Sequence 3 than in Sequence 1, so the identical frame (in same old pixel positions) are flashed in a different location of your retinas. So you get a double image during the eye-tracking situation.

For CRTs, they naturally flicker, so CRT 30fps at 60Hz looks like
Sequence 1 of 2 = flash a frame (CRT naturally flickers)
Sequence 2 of 2 = flash the same frame (CRT naturally flickers)

The constant is repeated flash of the same frame = duplicate image.

Eventually frame rate will get too low in the stutter-to-fluidity continuum, and it gets too difficult to track low-frame rates using an analog smooth pursuit of your eyeballs, and you might cease to see a double image effect at sufficiently low frame rates. Different humans have different sensitivities, but the variables are:
(A) Eye tracking.
(B) Smooth pursuit of eye tracking (not sudden start-stop-start-stop-start eye movement).
(C) Repeated flashing of identical unchanged/unmoved frames.
(D) Flickering that is generally close to or above your flicker fusion threshold.

So 10Hz flashing might not have a visible double image effect because some scientific variables may be violated. To make it easier to see double images at low refresh rates
- try increasing/decreasing brightness of your display and/or
- turning off your room lights and/or
- adjusting your viewing distance, such as slightly farther.
- adjusting the motion speed, such as faster speed motion.

Eventually your eyes may lock into a smooth analog pursuit without eyeball start-stop-start-stop effects (despite the digitalness of a finite frame rate and refresh rate) and the double image effect returns. The double image effect only occurs when your eyeballs are moving continuously (analog), creating different eyeball positions during those repeated flashes of the same unchanged frames.

An easy solution is to test a higher refresh rate (e.g. 120Hz+ LCD, 75Hz+ CRT, etc) to allow sufficiently high frame rates (and corresponding flicker frequencies) that are easier to analog-eye-track undistracted by the stutter of low frame rate (that may cause non-analog movement of eyes in a start-stop-start-stop-start-stop eyeball movement fashion)
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Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by Chief Blur Buster » 08 Nov 2021, 16:18

mynm wrote:
08 Nov 2021, 15:09
The first one is at 60 Hz and 60 fps, adding a half white path at the right of the ufo in one frame and at the right in the next frame. And what I get is more or less one ufo but the white mixed to its color. I see the same at the CRT and the LCD. You can see the video here.

And the seconf is to do the same to the 30 fps line and covering the repeated image. And I get the same and despite there are only 30 positions/fps for the image. You can see the video here.

[Editor's Note: These videos are invalid evidence as they are (A) not pursuit camera and/or (B) does not guarantee framerate=Hz at source & destination viewing public]
Those are not pursuit camera videos. And YouTube videos does not properly record the double image effect even when you eye-track the videos, because the frame rate of the video does not often exactly match the screen-recorder frame rate or camera frame rate.

So your videos are unusable evidence, unless there is proof of perfect framerate=Hz at source (camera recording) and at destination (played back to my screen). Direct TestUFO links is the only way to guarantee perfect sync with a random web browser viewer, e.g. TestUFO automatically adapts to the refresh rate of the display while videos do not. So frankly, screen recorders and camera recorders of this specific test is just invalid evidence.

You can only capture the double image effect via tracking eyeballs or tracking camera (pursuit camera), on properly-generated native frame rate like native HTML5 animations successfully synchronized to VSYNC.

The only way to do this is:
(A) Record/play at exactly the same refresh rate on source and destination display with zero frame drops, with a perfect screen record and a perfect video player. Unfortunately viewers may use 60.03Hz DELLs while screen recorder originally recorded on a 59/94Hz Hewlett-Packard. So video is not reliable, unlike a computer program such as HTML5 JavaScript that can VSYNC to the viewer display, like TestUFO does.
(B) Do a pursuit camera, where you pan the camera along the motion, to simulate a tracking eyeball. The resulting video, if recorded at the correct camera settings, can permanently preserve the effect independently of the destination refresh rate of the viewer's display. Pursuit cameras help you reduce the number of variables you need to control on the viewer-side.

If you want to learn how to use a pursuit camera with your iPhone or Android, please study the Pursuit Camera forum. With due respect, metaphorically you are trying to learn Grade 9 math without learning Grade 5 math.

Displays look different with stationary eyes(camera) versus tracking eyes(camera), e.g. www.testufo.com/eyetracking

Please allow me to embed the demonstration, for readers who are too lazy to click to animations:
1. Look at stationary UFO.
2. Look at moving UFO.
See? Displays look different for stationary eyes versus moving eyes.



Videos don't always successfully record 100% of all these kinds of effects. It works with the eyetracking animation, but fails with the software BFI animations, because of the refresh cycle precision required (e.g. custom framerate automatically adapted to viewer's display)

The same is true for the duplicate image effect.

To learn about pursuit camera, see my crosspost:
Chief Blur Buster wrote: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.)
You can try pursuit camera on the Software BFI images, and you'll be able to successfully record the double image effect into the video via a smartphone handwave-follow of the moving UFOs, as long as the camera exposure is sufficiently continuous to capture the entire multiple flashing sequence of whatever display CRT or LCD you use (e.g. 15fps at 1/15sec on a 60Hz LCD display, or 30fps at 1/30sec per frame on a 120Hz LCD display or 60Hz CRT display).

Then the double image effect is preserved in the recording, independently of the refresh rate of the display you play back the video on. That's a big advantage of pursuit camera videos; it eliminates a dependancy on the viewers' refresh rate, in reproducing the double image effect.

Ask yourself:
(A) Can you guarantee your screen recorder software records every single refresh cycle accurately at framerate=Hz
(Answer: Not always)
(B) Can you guarantee your video plays perfectly framerate=Hz on all viewer displays?
(Answer: Not possible, as different viewers have different refresh rates)

Your screen recording technique may work if (A) perfectly succeeds and you're recording/playing back on the same system, but may not work when playing back to a different users' system because the user may be running at a slightly different Hz.

If you want to eliminate some viewer-dependant variables, please use the pursuit camera technique (handwave iPhone with manually configured exposure settings) to simulate a tracking eyeball.
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mynm
Posts: 40
Joined: 23 May 2015, 06:36

Re: Software BFI Double Image Effect! (Emulation of CRT 30fps @ 60Hz)

Post by mynm » 08 Nov 2021, 16:48

Thanks for all the info and explanations it will take me a while reas and understand it. I will try to answer you properlly as soon as possible.

The videos are not recorded by a camera, are an onscreen record and where edited to do the tests. They are 60 fps videos and have 86 frames in 1.472 seconds. I think them are valid.

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