If you're sensitive to flashing images
I'd give this entire video a miss because it's full of them.
Hello there, I am Gav,
in this video we'll be learning how a 3D TV works,
using the help of slow motion as usual.
Specifically the kind that use these
active shutter 3D glasses.
Should probably start saying this is how a 3D TV worked,
because they're now relics of the past.
This video is sponsored by KiwiCo,
I'll tell you more about them at the end.
Before we look at the TV specifically
let's just go over the basics of what is actually going on
when you watch a 3D movie.
When watching content the illusion of 3D
is achieved by showing two different perspectives,
one to each eye.
This process is usually started in the camera
either by using a special 3D camera with two lenses,
or by using two cameras side by side to mimic the positions
of two human eyeballs.
For our VR180 series on Oculus
for our regular speed footage,
we used a camera with two lenses,
and then for the slow-mo we just use two Phantoms,
side-by-side.
Now the Phantoms are actually physically too big
to get that close together
especially once the lenses were on.
So we used a special mirroring,
one camera looking through a mirror
and one looking off the reflection of the mirror.
And this allowed the Phantoms to effectively
phase through each other,
giving the correct interocular distance.
From experience, I can tell you that this method
introduces a lot of extra costs and a lot of extra time
needed to complete the shoot.
I also wouldn't recommend handheld shots with this setup.
So now we have our two different perspectives,
left and right eye.
The next challenge is only showing
the correct perspective to each eye.
In a VR headset, it's actually quite simple.
You just have each eye look at a different screen,
or look through a different lens
looking at different areas on the same screen.
I won't go into too much detail about the other methods,
there's great videos online already.
But in a movie theater you would typically
project both perspectives using differently polarized light
and then un-powered glasses would filter those correctly
into each eye.
You can also use Anaglyph,
which typically uses red and blue filtering
to show each perspective to each eye.
We actually use this out in the field
just to make sure our footage was looking correct
before we could properly get it into post-production.
But it is a pretty ugly way to view 3D content
because the colors are just all over the place.
That brings us onto this TV.
It's actually a plasma 3D TV,
which I bought secondhand off Craigslist.
It's not in great condition,
there's all kinds of mess happening
on the left side of the screen
and the stand is taped on with a bit of gaffer,
but it should perform just fine for this demo.
The reason I went for plasma is that we can actually
get a bit of a double whammy here.
I've shown how CRT screens work, OLED screens work,
and how regular LED LCD screens work.
Never had a plasma TV before
and the way they work is slightly different.
Like an OLED TV, each pixel is self-emissive.
They don't need a backlight,
but they refresh the screen in multiple pulses per frame.
The entire screen can't be lit at full brightness.
So it ends up doing very short duration pulses
of different information in the frame
Persistence of vision in your brain
causes you just to see the complete image.
This is known as the sub-field drive
which often occurs up to 10 times per frame.
And the pulse is seen to last slightly different lengths
depending on where they are in building the frame.
Here I've stacked the results of each individual pulse.
Without even realizing it,
your brain will have stitched all of these together
creating what looks like just a normal frame of a movie.
Based on what we're seeing here this plasma TV
probably would have been advertised as a 480 Hertz display,
but that doesn't mean it's capable
of displaying 480 frames per second,
it just means that it's a 60 Hertz display
with eight pulses per frame.
So the way this differs from an OLED or an LCD TV
is that in slow motion, you can't actually see
the entire frame at once.
So now if we switch to 3D mode,
to the human eye without glasses on,
it looks like both perspectives
are just blurred over each other.
However, if I turn up my shutter speed on this camera,
removing a lot of the motion blur,
you can see that they're not just stationary
sat over each other,
it's flicking back and forth very quickly.
So now we know that once the TV has completed
building out one frame, it then switches perspective
to the other eye and builds the same frame
from that perspective.
This is where the active shutter glasses come in,
and their job is to make sure your left eye
only sees the left frame
and your right eye only sees the right frame.
And it does it by doing this.
Using a battery inside to power liquid crystal technology
inside each lens, very similar to what you would find
in an LCD TV.
It switches back and forth
blocking the vision from each eye.
This will happen 60 times per second, per eye.
That's 120 switches per second,
even on films that are only playing back
at 24 frames a second.
Looking through the glasses here in 3D mode
slowed down to 20,000 frames per second,
we can see that the TV now only has the capability
to pulse three times per eye for a total of six.
And I assume the remaining two pulses
are used to switch between left and right eye.
Well there we have it.
I honestly think that's such an interesting way to show
a different image to each eye
because the concept is so simple.
It's really just using technology to perform
advanced winking.
It honestly makes me a little bit sad
that the technology has been abandoned for new TVs
because you can get such big TVs now for so much cheaper
than they were back when this technology was being used.
And this makes more sense to me to have on a much screen,
otherwise it kind of looks like you're watching a film
in a box that's like a foot deep,
it doesn't make as much sense to me on a small screen.
Yeah, I never had one,
I guess I'm a part of the reason they went away
because I never bought a 3D TV.
This video was sponsored by KiwiCo,
very happy to have them back as a returning sponsor
to our videos.
They create fantastic projects and toys for kids
designed to introduce them to Science, Maths or Engineering.
This is a Eureka Crates,
so please enjoy some footage of me building some headphones.
KiwiCo have a campaign known as small today, big tomorrow.
The idea being that small lessons today
can mean much bigger world changing ideas in the future.
So by teaching the skills of innovation, creativity,
problem solving today will help them get a head start
better in the world in the future.
I've done several of these crates now
and my favorite thing about them is that
everything you need is in the box.
No need to go to the store,
you just plop down a crate, open it up and get going.
And it's very satisfying not having to
rummage around for extra things.
If you would like to support KiwiCo
and The Slow Mo Guys channel
you can get 50% off your first crate.
That's any of the crates
by going to KiwiCo.com/SlowMoGuys50
for 50% off.
If you found this video interesting
feel free to slop a like on it.
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make sure you subscribe.
Thank you very much for watching
and I'll see you in the next one, goodbye.