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Bass Jumping
February 13, 2011 4:33 PM   Subscribe

Shot with a Canon 5D MarkII at high shutter speeds, this video of a bassist's hand movements show a frequency that results in amazing string wobble (Vimeo; 1.11).
posted by bwg (70 comments total) 27 users marked this as a favorite

 
That's amazing. I wonder could you work out the notes he is playing based on analyzing the wavelength?
posted by a womble is an active kind of sloth at 4:35 PM on February 13, 2011 [2 favorites]


That is so awesome. I love it whenever the world is revealed to be such a magical place, just by seeing things differently.
posted by helmutdog at 4:38 PM on February 13, 2011 [3 favorites]


What the what? Pretty cool!
posted by Admiral Haddock at 4:39 PM on February 13, 2011


you can recreate this pretty easily with any stringed instrument and a strobe light. It's really cool. With a little tweaking of the hz, you can even get the string to stand still in a funky wobble like these.

I don't really see what is special about high shutter speeds that should produce this effect though. you could probably get it in any reasonable range of shutter speed.
posted by milestogo at 4:40 PM on February 13, 2011 [2 favorites]


Very cool. There's an argument in the comments on the link about whether this is really just a shutter speed thing or whether it's shutter speed plus the rolling shutter mechanism that's responsible for the wobble effect. My brain's not really up to tackling that head on but I'm inclined to go with the latter—a lot of the apparent waveforms of the strings don't make any goddam sense based on my understanding of the mechanics of the acoustic vibration of a string in time.

I don't really see what is special about high shutter speeds that should produce this effect though.

I think the issue is that at a lower shutter speed, the string will manage to make a pretty significant transit during the capturing of each frame and so instead of getting a crisp string you'd get a motion blur. High shutter speed means the string is going to be more effectively "frozen" in each frame.
posted by cortex at 4:45 PM on February 13, 2011 [4 favorites]


Visually amazing.

That's some pretty stiff bossa nova that band is playing, though.
posted by flapjax at midnite at 5:06 PM on February 13, 2011 [3 favorites]


This is how Salvador Dali sees the world...
posted by schmod at 5:06 PM on February 13, 2011


At a lower shutter speed, the string motion will blur. Compare, for instance, photo of a waterfall at a high shutter speed vs a slow speed. I think, in this case, we're seeing a stroboscopic effect: the shutter speed and the frequency are close enough to reveal the string vibration.
posted by jdfan at 5:22 PM on February 13, 2011 [1 favorite]


you can recreate this pretty easily with any stringed instrument and a strobe light. It's really cool. With a little tweaking of the hz, you can even get the string to stand still in a funky wobble like these.

I discovered this as a teenager, lying on my back and idly plucking a guitar while watching TV. Put a string in your vision between the screen and your eye and you can watch the strings undulate lazily.
posted by ricochet biscuit at 5:24 PM on February 13, 2011 [1 favorite]


That's some pretty stiff bossa nova that band is playing, though.

How insensitive of you to say that.
posted by sourwookie at 5:26 PM on February 13, 2011 [5 favorites]


...the string will manage to make a pretty significant transit during the capturing of each frame and so instead of getting a crisp string you'd get a motion blur.

That. The waves travel up and down the string from the plucking point, are in part absorbed/transferred to the instrument at the outer ends of the string, but part of the waves travel back along the string, overlaying the preceding pattern, while the string as a whole vibrates in the sounding frequency as well; this accounts for a massive blur, which only can be stopped down into discernible patterns by looking at really small time-sections.
There's quite some research going on about this in a geeky corner of organology, and what I've got out of the people I've talked to, they're having a pretty hard time figuring out what a string exactly does when it does what it does.
posted by Namlit at 5:30 PM on February 13, 2011 [1 favorite]


How insensitive of you to say that.

Not as insensitive as that drummer's performance...
posted by flapjax at midnite at 5:30 PM on February 13, 2011 [6 favorites]


Pssssssst! For those not in the know, "How Insensitive" is the name of the Jobim song they're, ahem, playing.
posted by sourwookie at 5:35 PM on February 13, 2011 [8 favorites]


cortex: "There's an argument in the comments on the link about whether this is really just a shutter speed thing or whether it's shutter speed plus the rolling shutter mechanism that's responsible for the wobble effect."

Yeah, this. If you think about it, the wavelength of an upright bass is measured in several 100's of centimeters; let's say ~8600cm (40Hz) to ~860cm (400Hz). A rough guess, based on the width of his hand, puts a complete wave shown in the video at ~20cm, or somewhere around 18,000Hz (18KHz, above the audible range of most adults). So yeah, while the shutter speed is fast enough to 'freeze' the string, what's visible in the video is an artifact of either the recording frame rate or a rolling shutter.

Still, it does look cool…
posted by Pinback at 5:36 PM on February 13, 2011 [1 favorite]


sourwookie, I love you.
posted by flapjax at midnite at 5:39 PM on February 13, 2011


I think we are seeing some wagon wheel effect.

On a stringed instrument, the fundamental note has a wavelength of the length of the string from the bridge to the nut or the finger stop point.

So the strings are moving at the amplitude we are seeing, but they are NOT actually moving at that frequency. A wavelength of a couple inches is going to be really high. Half the string is the next octave up, right? Some of those apparent waves are like a 1/32 of a string. I don't think we can even hear an E24. And a string under that kind of tension can't wiggle like that.

I think the math is the HZ of the note divided by the FPS of the camera is how many nodes we see. 440-A divided by 60 fps is going to be about 7 apparent waves.
posted by gjc at 5:44 PM on February 13, 2011 [2 favorites]


But yes, that is fucking cool to see. We are seeing the motion of the strings, just through a funhouse mirror of sorts.
posted by gjc at 5:46 PM on February 13, 2011


And because of the pollution of public discourse by corporations, it's nearly impossible to tell if all the mentions of exactly which camera this is are because it's a viral or because it's technically interesting.
posted by DU at 5:50 PM on February 13, 2011


First things first - this isn't a "shutter" issue - it's an artifact of the way CMOS sensors are read out. The mechanical shutter (jaw-dropping animation here) is open the entire time this is happening.

CMOS image sensors (like the image sensor in the 5D MKII) don't just dump their image out all at once. In fact, they are read out from top-to-bottom.

That means that when you take a still picture, the first row of pixels is read out into the image processor. Then the next row, and then the next, until all 3,744 rows of 5,616 pixels are read out and moved on to the next stage of processing.

All 3,744 rows must be read out before the exposure completes (meaning that the shutter completes is transit -- remember the animation?). So if the "shutter speed" (which means the total time that the shutter is not closed) is 1 second, the rows are being read out at least 3,744Hz. But let's be really clear here - the shutter has very little to do with this readout. The shutter's job is to keep the sensor dark. For still photography, the shutter opens, the sensor is electronically read out, and the shutter closes. For videos, the shutter is held open the entire time and the sensor is read out at video rates.

The readout that causes this visual artifact is almost completely separate from the mechanical shutter that most of us are familiar with (or in fact, not at all familiar with, as I have learned talking to most photographers and photography buffs, who deeply misunderstand the role of the shutter in modern cameras). For more on that, watch this excellent video.

In this particular case, more realistic readout values (meaning, time to read every row from top to bottom) are like 1/100th of a second. So the image is being read out, top to bottom, row to row at 374,400hz. As each row is read out from the sensor, the position of the string changes slightly because it is vibrating. Because the vibration is traveling along the string, which is nearly vertical in this image, the effect is enhanced. In other words, if the instrument were horizontal such that the fretboard were parallel with the top of the image, this effect would look very different.

Now, in truth, the 5D doesn't actually read out all 3,744 rows when it is doing videos, in fact, it skips every third line or something. So my numbers are off, but I didn't want to get lost in details right away. Suffice it to say that the actual readout is much slower than the almost 400khz I mentioned above - in fact, it is just fast enough to cause artifacts at audio frequencies.

Now some people think that this is an artifact of digital photography, and make a big stink about "rolling shutter artifacts", but in fact rolling shutter has been with us since the very early days of picture making due to mechanical "rolling curtain" shutters. Jacques Henri Lartigue photographed a race car with a film camera that has a shutter which slid across the film plane from bottom to top. So when the first part of the film was exposed, the wheel was further back in time than when the last part was exposed.

In this way, most cameras, old and new, actually capture a bit of time along with a bit of space. Fascinating stuff. Gawd, I love cameras.
posted by fake at 5:54 PM on February 13, 2011 [56 favorites]


And btw, there are about a million examples of this effect out there - check out this airplane prop that appears to be frozen in time.
posted by fake at 5:56 PM on February 13, 2011 [1 favorite]


Not as insensitive as that drummer's performance...

I had to listen to that a second time to notice that there was a drummer. first time around i thought it was random traffic noise or traffic or something.

and now thanks to fake i don't need to say anything further about shutter speed/frame rate/rolling shutter.
posted by mexican at 5:58 PM on February 13, 2011


gjc, agreed about the wagon wheel effect - I was to say "also tentatively agreeing about the shutter-artifact idea" but I was, too, doubtful because rolling shutters have been around for a while etc. Thanks Fake for the explanation. It seems like that the flabby spaghetti effect here doesn't show what actually happens.

About the vibration patterns, see my earlier comment. Problem is that a string plucked somewhere in the middle does initially two things: 1 it moves at its frequency, that is: whole string up and down; 2 The pluck travels up and down the string. If you have a strong pluck, you're getting quite a neat secondary amplitude. Then there are all sorts of interfering patterns and partials that make the pattern even more complicated. If you randomly depict selections of all this, apparently, you get spaghetti non al dente.
posted by Namlit at 6:01 PM on February 13, 2011


slid across the film plane from bottom to top.

Technical error, it's top to bottom but the image on the film is upside-down. Reverse as necessary and I'll not correct myself further.
posted by fake at 6:06 PM on February 13, 2011


Well, this confirms my biggest hopes and worst fears.

Cartoon physics is a much more accurate model of the real world than classical Newtonian physics.
posted by loquacious at 6:27 PM on February 13, 2011 [2 favorites]


I came up with a chord chart with the chord roots and fifths (most common Bossa bass pattern) that I converted into the frequencies with each note. The normal key for this song is D minor, they're doing it in Bb minor.

I suppose someone could use this to figure out what is happening with the camera shutter/scanner/whatever by using these numbers.

I don't know how to format a table in the blue. If someone could hep me to it I'll gladly repost.

Time Chord Root/Freq(hz) 5th/freq(hz)

:07 Bb- Bb/117 F/87
:09 Adim A/110 Eb/78
:12 Ab-6 Ab/104 Eb/78
:15 Eb7/G G/98(196) Bb/117
:18 GbM7 Gb/93(185) Db/156
:21 BM7 B/124 F/87(175)
:23 Cdim C/131 G/98
:24 F7b9 F/87 C/131
:26 Bb- Bb/117 F/87
:29 A7 A/110 E/41/82
:30 A sloppy edit happens

It just so happens that I'm a Jazz upright player with a degree in audio engineering. Couldn't resist making the chart.
posted by sourwookie at 6:33 PM on February 13, 2011 [15 favorites]


sourwookie, that is some impressive sonic nerdery.

:30 A sloppy edit happens

That cracked me up.
posted by flapjax at midnite at 6:36 PM on February 13, 2011


If what we see is Hz/FPS then certain notes will make the string appear very slow. Bb's, B's, and C's especially so with periods of .96, 1.03, and 1.08 respectively. In fact a Bb would appear almost motionless.
posted by sourwookie at 6:50 PM on February 13, 2011


Just to add to fake's excellent discussion of rolling shutter, CCD sensors can be constructed with a frame-transfer buffer and simulate a global shutter. However, compared to CMOS, the production cost, the power consumption and the number of transistors in CCD is much higher.

My experiments with the sensor in the Canon 5D and 550D show that the scan time is about 25 usec/raster line, limiting the maximum 1080p frame rate to only slightly more than the 30 fps. The video modes can have higher shutter speeds (as shown in the bass video), but the actual frame always takes about 27 ms to scan.
posted by autopilot at 7:11 PM on February 13, 2011 [2 favorites]


So 37 FPS then? I could build a table showing period for each note used if I know the FPS of the video.
posted by sourwookie at 7:19 PM on February 13, 2011


Cool find, thanks.

As an amateur musician, I find that people who have to snark and nit-pick about reasonably good musical performances are just jealous. :-)
posted by randomkeystrike at 7:30 PM on February 13, 2011 [1 favorite]


Well, sometimes they're reasonably good musicians with informed opinions.
posted by cortex at 8:03 PM on February 13, 2011 [1 favorite]


autopilot, I really admire your work. Thanks for the final word on actual readout times. There's an argument among some engineers I know revolving around these numbers.
posted by fake at 8:04 PM on February 13, 2011


And a string under that kind of tension can't wiggle like that.

Wait, what? String bass strings are taut, but not really under the kind of tension you'd find on a guitar or violin or whatever. But they really move around a lot when you play them, even with a bow. It's quite easy to move them more than an inch simply with one's fingers. Of course they're going to wiggle like that, just way too fast for your eye to see it. If the string doesn't actually move a specific distance, then it won't actually make a specific sound.

Plus, if you're playing acoustic bass in a jazz trio, you're really playing the hell out of that instrument, just to get the pizzicato to be heard over the piano and drums.
posted by hippybear at 8:35 PM on February 13, 2011


Here in Milwaukee there's a museum called Discovery World that has a little display like this. There is a big wheel with black and white stripes on it behind some black nylon guitar strings. You spin the wheel and pluck the strings, and you can see the "wobble." Lucky for you guys, I shot a little bit with my phone last time I was over there. And remember, this is not an artifact of the phone, this is what you see with the naked eye.
posted by buriednexttoyou at 8:41 PM on February 13, 2011 [2 favorites]


Wait, what? String bass strings are taut, but not really under the kind of tension you'd find on a guitar or violin or whatever. But they really move around a lot when you play them, even with a bow.

I think gjc meant that they won't wiggle at that apparent wavelength; the amplitude is completely sensible, but the apparent wavelength is much too short.
posted by mr_roboto at 9:00 PM on February 13, 2011


Ah. Well, no string that is fixed at both ends can really wiggle in a visible wave like that. I must have misunderstood.
posted by hippybear at 9:06 PM on February 13, 2011


buriednexttoyou, that is an awesome example of a shutter artifact. note how the wave form for the middle note appears to have a higher frequency than the low note. very cool.

this is a good demonstration that the apparent wavelength isn't particularly meaningful in video shot like this. you're not seeing a true representation of the sound wave but a reconciliation between the string vibration and the video capture method. if you play enough with either the frame rate or string frequency you could make just about any wave frequencies you wanted, and maybe even something that looked like a straight line (like the propeller in fake's prop frozen in time video).
posted by mexican at 9:09 PM on February 13, 2011 [1 favorite]


if you play enough with either the frame rate or string frequency you could make just about any wave frequencies you wanted

I'd have to know more and have better comparison to say much about how frame rate or CCD performance would affect how things look on this kind of video...

...but wouldn't playing with the string frequency actually be changing the note, and therefore you could draw meaning from it?
posted by hippybear at 9:20 PM on February 13, 2011


changing the string frequency would also change the note, but rather than getting video of a wave that goes from low apparent frequency to high apparent frequency in a direct relationship to the pitch, you'd get waves that alternate between from high and low apparent frequencies with blurry sections in between depending on the frequency:frame-rate ratio. just like when you watch video of a fan blade or car wheel, it will speed up, slow down, appear to stop, then go forward again, then get blurry. you're not watching actual motion but rather a stream of still pictures, and sometimes you'll see unusual movement or physical attributes (like a bending propeller or warping string) as a result of the technology used to capture the images.
posted by mexican at 9:33 PM on February 13, 2011 [1 favorite]


The chart upthread I created gives you the actual frequency of the string for the note played at specific times in the video--I figured it out for y'all already. If you take that value and divide it by the frequency at which the pictures are taken (I have no idea if that is determined by shutters or sensors or even a frame rate setting in editing--I'm waiting for the camera geeks here to give me that number) then that value is the frequency we end up seeing. This is really pretty cut and dried provided someone can supply the info on the video capture rate.
posted by sourwookie at 9:49 PM on February 13, 2011


Oh, and on that table ":23 Cdim C/131 G/98" SHOULD READ ":23 Cdim C/131 Gb/93". Sorry.
posted by sourwookie at 9:53 PM on February 13, 2011


Thanks for the explanation. I'm a bear of very little brain, and you made it clear.
posted by hippybear at 10:04 PM on February 13, 2011


the actual frame rate is not specified by the video uploader, the the 5D Mark II will either do 29.97fps or 23.976fps. it's probably 29.97fps (30fps).
posted by mexican at 10:08 PM on February 13, 2011


This is really pretty cut and dried provided someone can supply the info on the video capture rate.

The thing is, there isn't really a single-frame video capture rate that's relevant to this purpose. As fake described, the frame is read in row-by-row, so the string continues moving as the image is captured. The apparent motion of the sting is an artifact of this "rolling shutter".
posted by mr_roboto at 10:09 PM on February 13, 2011


Well, no string that is fixed at both ends can really wiggle in a visible wave like that.

you've never played a 5 string bass, then - that bottom b string flops around like a fish
posted by pyramid termite at 10:30 PM on February 13, 2011


Video Stroboscopy of the Vocal Cords
posted by finite at 10:55 PM on February 13, 2011


Fake gave a very good explanation of how CMOS digital camera chips do their thing, but it really doesn't matter to this video; as has been pointed out, you can see the same effect using a strobe light. The reason the string looks all wavy is because it IS all wavy! with a short shutter speed, we see only one of the vibrational frequencies. Mr. Roboto - there is no apparent motion
- the string is in motion. How else is sound created?

Just to be clear, this is a sort of "the wagon-wheel effect". It is not due to the "rolling shutter effect".
posted by Steakfrites at 11:55 PM on February 13, 2011


Steakfrites: Buriednexttoyou's video uses something like a zoetrope, not a strobe light, so it's more like a rolling shutter. Unless I'm misunderstanding what's going on here the strings are never really stretched like that at any moment in time. So, it's not like the wagon wheel effect.
posted by Pruitt-Igoe at 1:30 AM on February 14, 2011


From estimating the wavelength of the waves (5-10cm) it deceptively appears we are seeing some of the upper harmonics. this is possible as the string's actual motion is a harmonic series of sine waves super-imposed, but the term with by-far the highest displacement is the fundamental---and we see some pretty high displacement in the video.


in actuality its oversampling the strings fundamental harmonic motion. by the time each subsequent line is read, the string has moved a little one way or the other. the "nodes" we see are when this oversampling completes a full cycle of the strings motion.

to use autopliots 25usec line readout period, you see two to six standing waves across the 1080 line frame we are looking at string frequencies of 74Hz, 111Hz, 148Hz, 185Hz, 222Hz, respectively. the waves that appear to move along the string are in between frequencies that are out of phase, and so they crawl up and down the string at even lower beat-frequencies. these frequencies are roughly in line with sourwookies numbers.

what looks very similar the (inter-frame) wagon wheel effect, is actually (intra-frame) rolling shutter in the digital sense (or more precisely its an aliasing effect).
posted by dongolier at 2:19 AM on February 14, 2011 [1 favorite]


I discovered this as a teenager, lying on my back and idly plucking a guitar while watching TV. Put a string in your vision between the screen and your eye and you can watch the strings undulate lazily.

I was gonna say this, too. Try it at home!
posted by snofoam at 3:54 AM on February 14, 2011


I discovered this as a teenager, lying on my back and idly plucking a guitar while watching TV. Put a string in your vision between the screen and your eye and you can watch the strings undulate lazily.


Indeed - If you look at a TV through a plucked open G string it's possible to tune very close to concert pitch.
posted by the noob at 5:21 AM on February 14, 2011


Hey pal, last time I saw an open G string, a TV was the last thing I wanted to look at! HYUK HYUK HYUK

/rim shot
posted by flapjax at midnite at 5:52 AM on February 14, 2011


And remember, this is not an artifact of the phone, this is what you see with the naked eye.

Just note that this is almost never true. Your phone will also use a CCD with a rolling readout of the lines, and so the light hitting the top and bottom will be from different slices of spacetime.
posted by odinsdream at 6:12 AM on February 14, 2011


Also - this discussion is fascinating - thanks to all who are contributing. It really highlights how amazing it is that our day-to-day human experiences are reliant on sensory information that covers only a very specific way of interpreting spacetime.
posted by odinsdream at 6:16 AM on February 14, 2011


I think that buriednexttoyou's video from the science place is probably the most illustrative of how this camera artifact is working, if I'm understanding this all correctly.

Because that science place exhibit is actually creating a rolling shutter for your eye, because of it being a series of slits you're viewing the strings through, rolling quickly past your eye. Just like the scan on the CCD rolls past as you record video.

This is all so very fascinating, and I'm seeing the world more clearly now thanks to this thread.
posted by hippybear at 7:06 AM on February 14, 2011 [1 favorite]


Yeah that demonstration from buriednexttoyou is fantastic - and "creating a rolling shutter for your eye" is not only a great idea, it's the perfect way to describe it.
posted by fake at 7:31 AM on February 14, 2011


I thought it might be good idea to try to recreate this, in order to sort out the Wagon Wheel v. Rolling Shutter dispute. After the experiment, I think in this case that everybody's correct! It's a little of one and a little of the other.

I took a guitar, and 2 video cameras - a Canon XHA1 (CCD - no roll), and an XF300 (CMOS - some shutter roll).

With the XHA1, I increased the shutter speed to 1/1000 and plucked the G-string. In the viewfinder I could see the string waving back and forth slowly. It was a little like the original video, but the wavelength seemed much longer and the motion lazy.

I then tried the same with the XF300 and saw the exact same effect. Then I rotated the camera 90°, and - wow- little squiggles all over. The camera must be perpendicular to the string to get the effect. (This would explain the Zoetrope showing the same effect.)

I conclude that a short shutter helps isolate and freeze the vibrations of the string, but the real crazy dipsy-doodles are indeed from the rolling shutter effect.

I haven't included any video because I'm too busy right now to set up lights, and these high shutter speeds need a lot of light. The viewfinder image was too dark to post, but I'll do it when I have the chance.
posted by Steakfrites at 7:48 AM on February 14, 2011 [1 favorite]


Can't wait to see those videos on YT. :)
posted by fake at 7:57 AM on February 14, 2011


Just note that this is almost never true. Your phone will also use a CCD with a rolling readout of the lines, and so the light hitting the top and bottom will be from different slices of spacetime.

odinsdream, that's true, but when you look at this exhibit with your own human eyes, you see what's represented in the video. If anybody wants come up to Milwaukee and see it yourself, I've got a membership at Discovery World and I think I get to bring one free guest. We could make a day of it.
posted by buriednexttoyou at 7:58 AM on February 14, 2011


buried, that's because the thing is creating an equivalent rolling shutter!
posted by fake at 8:02 AM on February 14, 2011


Nevermind me, I know you know this.
posted by fake at 8:05 AM on February 14, 2011


I agree with the rolling shutter theory. I tested Steakfrites' experiment with my Canon T1i, and there is definitely a different effect depending on the tilt of the camera. There are several settings on mine, in 720 the framerate is ~30fps, and the effect isn't really there, but at 1080 the camera can only do ~20fps, and that's where you can see it (although it's not nearly as cool as the video in the post). I'll see if I can get my video on YouTube.
posted by buriednexttoyou at 8:19 AM on February 14, 2011


Ok, here's my little video. It's not 1080 on the web because I didn't want to wait forever uploading it, but you get the idea.
posted by buriednexttoyou at 8:41 AM on February 14, 2011 [2 favorites]


Let's not turn this into a "will-an-airiplane-on-a-treadmill-take-off" argument, otherwise asavage might have to get involved.

Actually, lets!
posted by howling fantods at 10:16 AM on February 14, 2011


Maybe someone wiser can riddle me this: what "shutter speed" does the human eye achieve? I've heard that if a pigeon was to watch a film played at 24fps, it would see only still images, because it's brain processes those images faster.

For all we know, pigeons see shit like this all the time.
posted by Acey at 11:52 AM on February 14, 2011


Maybe someone wiser can riddle me this: what "shutter speed" does the human eye achieve?

Vision doesn't really work this way; we don't capture consecutive images. Instead, the brain is constantly processing a stream of visual information. We begin to perceive a series of consecutive still images as fluid motion at around 20-50 images per second.

Because human vision doesn't work as single-frame-capture, you don't get these kind of frame- or line-capture artifacts when viewing the world unmediated. There are a bunch of artifacts associated with human vision, however, and these are used by vision researchers to understand the mechanisms (physiological and cognitive) of vision. These artifacts are called "optical illusions".
posted by mr_roboto at 12:01 PM on February 14, 2011


mr_roboto is dead on. FWIW, you can change the overall "speed" of one of your eyes by placing a dark filter over one of them. That's known as the "Pulfritch effect", and it's sometimes exploited to make 3D imagery by delaying the signal from one eye to the other.

Some insects, such as houseflies, "see" fast enough that the blinking of fluorescent lights is visible to them.
posted by fake at 12:11 PM on February 14, 2011


Another cool video effect posted in the comments
http://www.youtube.com/watch?v=LVwmtwZLG88
posted by jeffmik at 12:36 PM on February 14, 2011


Acey: what shutter speed is the human eye?

there is no shutter, or... to stretch the metaphor, there is an electronic shutter for each rod and cone cell.

cones integrate signal over about 20ms (55Hz) while rods go up to 100ms (10Hz).
(p510 Kandel, Jessel, Schwartz [3Mb PDF])

no need to ever go above 60 frames per second video...
posted by dongolier at 3:52 PM on February 14, 2011


Which leads to the question... do all of those cones and rods integrate their signals simultaneously, or are they all working out of synch so there is a more continuous stream of visual information into the visual cortex?

And yeah... 60 fps... That's the threshhold which led to the development of the Showscan system. Sadly, never widely implemented. (Actually peaked out at 72 fps.)
posted by hippybear at 3:59 PM on February 14, 2011


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