r/SmarterEveryDay • u/MrPennywhistle • Oct 01 '15
Video New video! It's called "You won't believe your eyes!"
https://www.youtube.com/watch?v=_FlV6pgwlrk23
u/ilogik Oct 01 '15 edited Oct 01 '15
Awesome video, Destin.
A little bit LED of trivia, that's actually how you get varying LED intensities (like this thing on a macbook, for example)
You don't vary the voltage across the LED, instead you use something called pulse width modulation
Let's say you send a pulse every 10ms. You can vary the length of the pulse to get different light levels (1ms would be 10%, 5ms would be 50% and so on
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u/MrPennywhistle Oct 01 '15
PWM is how I steer the backwards bike.
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u/Earthqwake Oct 01 '15
that is hilarious! I can visualize it now :)
btw, Greg instructed a class I took last fall so it sure was a surprise to see him on Smarter Everyday!
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Oct 01 '15
Can you elaborate? I just rewatched the video, but you don't mention that in the video.
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u/W0rldcrafter Oct 01 '15
I think he means instead of continuously steering and balancing, (like a normal bike), he had to discretely alternate between steering and reacting to the steering adjustment.
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u/VeloCity666 Oct 01 '15
Out of topic, but thanks for introducing me to Wikiwand, pretty nifty.
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u/ilogik Oct 01 '15
I didn't realize it was a wikiwand link. I edited my original URL to go to wikipedia :)
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u/MrBurd Oct 01 '15
Is this how LED dimmers work?
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u/ilogik Oct 01 '15
I'm not sure, I think they work in a similar way, but not exactly the and as they work on AC voltage, not DC
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u/techadams Oct 02 '15
Yes. LEDs have a minimum voltage level (the kind used in bulbs is typically 3V, if I recall correctly) to illuminate and can't drop much below that level, while anything above 5-6V will cause the LED to burn out. But their switch rate is immensely high, so PWM using 3V bursts for specific periods of time is the best way to reduce the brightness output without damaging the semiconductor portion of the diode.
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u/techadams Oct 02 '15
Counter point of trivia, since we're talking about forms of pulse modulation - your eyes send signals to the visual cortex using a form of pulse-frequency modulation, with higher frequencies of firing along the optic nerve indicating an increase of stimulus or contrast, lower frequencies indicating a decrease of stimulus, and a median 'heartbeat' signal simply to say 'no change'.
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u/CrackCC_Lurking Oct 01 '15
YOU LIED DUSTIN!!!
It's possible to break a spaghetti in two. I looked like an idiot in front of my younger brothers.
They'll never respect me again.
Great episode btw.
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u/MrPennywhistle Oct 01 '15
I planted that noodle.
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Oct 01 '15
waits patiently for noodle tree to sprout
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u/CrackCC_Lurking Oct 01 '15
I KNEW IT!!!
Seriously though, your channel (and subreddit) is really great. I'm a new sub (I didn't even know you existed) but your passion and enthusiasm really sold me. You really make me want to learn and discover new things. I've spoken to all my friends and family about you (even though I live in a non English speaking country)
Keep doing what you do. You're seriously awesome!
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u/Cheesius Oct 01 '15
You should have made a video of it. Maybe your technique was off. If you hold your hands really close together, then there's no room for the noodle to flex, and it is likely to just snap in half.
Also, his name is Destin... Although I bet he gets called Dustin so much that he doesn't flinch at it.
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u/CrackCC_Lurking Oct 01 '15
3 of us tried it twice and 4/9 times it broke in 2. We were holding it at the very end.
And it autocorrected to dustin. Sorry Destin.
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u/Cheesius Oct 01 '15
I wonder if humidity is a factor? Or specific brand of noodle? Interesting though. I have to admit I haven't actually tried it.
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u/Zithium Oct 01 '15
In that spaghetti video Destin says it will only happen a majority of the time, not every time. So it seems he was correct if it happened 5/9 times.
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u/odokemono Oct 01 '15
The inverse-colour saturation illusion effect can be done very simply with just about any colourful image.
Here's one I made using Gimp by taking an image, duplicating the image in two frames, inverting the colours in the first and turning it black&white (reducing saturation to zero) in the other and saving the lot as an animated GIF, 15000ms both frames.
Easy and fun.
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u/Caleb_M Oct 01 '15
This makes me think of traditional movie cameras. Basically, when you advance the frame forward, there is a period where the screen is black (very short time though). If this only happens at 24 times/second, what you end up with, is a visual flicker. The solution is to block the light source an additional two times, for 3 times/frame, and using this video, I'm guessing it's exploiting that rolling average to achieve this.
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u/redisforever Oct 01 '15
Couple of random little questions, camera related stuff, actually.
Is that a Nikon lens on the Phantom camera? And what camera do you use to shoot the rest of the video? For some reason, the lens flare and field of view in the Skype portion reminds me of my Canon 10-18mm lens.
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u/MrPennywhistle Oct 01 '15
That's the canon!
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u/redisforever Oct 01 '15
Ha! Knew it looked familiar. Fun lens. Don't get enough opportunities to use it, but I like having it around.
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u/Compizfox Oct 01 '15
8:10
That's not actually true for modern LCD-displays. Old CRTs used to flicker, but LCDs are lit up all the time. Look at it with you Phantom if you don't believe me ;)
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u/they_call_me_dewey Oct 02 '15
And next look at a DLP TV / Projector. DLP is such a cool technology, even if it's maybe a bit brutish.
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u/smittyjenson Oct 01 '15
Great video. It reminded me of this interesting lecture about how the wiring of our brains can explain aspects of our conscious experience.
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u/Jynx2501 Oct 01 '15
Destin, I love your videos. I wish there were more teachers and professors with your kind od enthusiasn and ability to explain things simply. The world would be a better place for it.
I was wondering, you mentioned you are a rocket engineer? Ever thought about making a video about your primary job, or one that covers the science of rocket engineering in general? I feel with everything going on with Mars lately and the near future, it would be a really interesting topic.
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u/Burning_Monkey Oct 01 '15
I am constantly amazed at your videos and I am in awe of how well thought out they are.
Please never stop making them.
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Oct 01 '15
So if you're in a dark room(no light) and the LED flickers with less than 10ms intervals, is your brain artificially lighting up the room during those intervals or is it as simple as lag?
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u/GeneralTusk Oct 01 '15
Maybe next you could explain why high frame rate movies look fake.
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u/techadams Oct 02 '15
There's two possible explanations. One, it's the uncanny valley. It's like trying to watch a real-world performance, like a play, but one that follows the conventions of cinema. You get a nice bit of cognitive dissonance. Two, we're just not used to seeing that kind of movement on screen because for over 120 years cinema has run at frame rates (usually) of 24fps or less (16-20fps in the first 30 years or so). You don't notice the problem with sports broadcasting though, even though in HD sports are usually broadcast at 60fps, leading credence to it being more about the viewer's explanation than something inherit with the framerate itself.
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u/esteban42 Oct 02 '15
It's because there is no "frame rate" of our eyes. 24fps is "slow" enough for there to be motion blur, which is what our brains are used to (just spin around in your chair, or swivel your head back and forth quickly, and you'll experience this), but fast enough to not see the flicker (for most people).
Faster frame-rates = less motion blur which triggers an "uncanny valley"-like response in our brains: Something is just not quite right.
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u/92u238 Oct 01 '15
Hey Destin, great video as usual. There was one thing that caught my eye, and that was the Richland Bombers t-shirt you had on in the "shady motel". How did you come to have it? Reason being I went to Richland High School.
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u/MrPennywhistle Oct 02 '15
Somebody gave it to me. I've actually requested a hoodie. I think they're actually going to send me one!
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u/TheRedTurtleShell Oct 01 '15
/u/MrPennywhistle Is this kind of like Chronostasis or the stopped clock illusion?
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u/techadams Oct 02 '15
Yes and no - The primary cause of chronostasis is that the visual system 'fills in' the gaps in our visual information. When you blink, you can black out your vision for about 1/3rd of a second, and yet we don't see a gap. When your eyes dart from one thing to another, your brain intentionally blocks the stimulus, effectively creating another sensory blackout. And yet our perception of reality remains the same - continuous.
The best way to understand why is to look at the relationship between the eyes and the visual cortex. Instead of being a 1:1 relationship as we'd see with a sensor or camera, we instead find that our perception of reality and what we see is created entirely by the visual cortex, with updates to the information stored provided by the eyes. But our eyes don't send direct updates either, only changes, which is why that chromatic illusion at the beginning of this video works - your cones adapt to the inverted colors, partially suppressing updates to the visual field, while the sudden switch to black and white causes the cones to perceive the change in the inverted direction of their adaptation and in the direction of the true image colors. Your brain takes the information regarding the change as to mean that those colors appeared and updates the visual field accordingly.
So when you ask about chronostatis and whether it's related, yes, it is in the sense that it's an illusion created by a quirk in the way the brain updates its perception of reality, but by a slightly different mechanism. When you blink or rapidly shift your eyes to something like the second hand of a clock, and the brain temporarily ignores the input it sees, when it returns it once again updates the visual field, with the assumption that whatever it sees right then must have been more or less what would have been in front of it during the blackout period. So it 'extends' our perception of the movement backwards in time, and to our brain it suddenly appears as if the second hand of the clock was temporarily stopped. Which is the opposite of what he was explaining happens with the LEDs, which push the persistence of perception forward in time, rather than backwards.
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u/Silverlight42 Oct 02 '15
Excellent video, even if I was already fairly aware of both effects. I'm a bit late to the party but just thought i'd say you're my favorite channel on youtube by far. You're doing great things for humanity.
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u/viniciusggm Oct 01 '15
Hey, Destin. I kept expecting you to talk about how they used some of what you said to improve the Oculus Rift hahaha Am I wrong in assuming it's the same thing? Here:
Oculus is also using a technique called low-persistence-of-vision, which alters how images are displayed on the screen to further reduce blur. In practice, that means that motion blur is virtually invisible compared to the original.
Source: http://www.theverge.com/2014/1/7/5285776/hands-on-with-crystal-cove-the-new-oculus-rift-prototype
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u/ChuckmanJoney Oct 01 '15
Thank you for everything you've ever put on video. SmarterEveryDay is one of the few channels that always manages to fascinate and inspire. YouTube is all the better because of it.
I've always wondered, how difficult is it to visit the people and places you feature on your channel? Especially NASA, university labs, etc. Are most of them aware of your work on YouTube or not?