I'm in Tromsø in Norway,
That is the Tromsø bridge,
and the beautiful Arctic Church there.
Now, if you've been following my videos from here for the last couple of days,
you might have noticed something a bit weird
every time I'm under artificial light.
And let's be honest: That's most of the time.
Because, while it does get light in the middle of the day here,
we're in the Arctic Circle,
it's winter.
The sun doesn't get above the horizon.
Mind you, when it does get light, this place is beautiful.
Anyway, you might have seen a bit of a weird effect,
if I take a slow motion video of that streetlamp, and the ground under it,
you'll see what I mean.
There's this kind of weird strobing, rolling effect going on.
And the reason for that,
is something you might not know,
the difference between the European and American power grids.
See, the European power grid runs at 50 hertz,
50 cycles a second.
That means the alternating current in the wires
switches direction,
a hundred times a second, 50 cycles
back and forth, back and forth
And that means all these lights, that you can see,
pretty much, dim imperceptibly
a hundred times a second.
Not enough that you can see it with the naked eye,
but the camera will pick it up.
Now, okay, that's not a major problem
if your camera runs at the same rate as the lights
The lights run at 50 hertz,
British television runs at 50 hertz.
But unfortunately, I'm using an iPhone,
which is designed in the U.S.,
for the American power grid.
The American power grid chose to run at 60 hertz,
60 cycles a second,
so American TV runs at 60,
or 30 frames a second.
So, the camera is recording at 30 frames a second,
the light is pulsing at 50 hertz,
those two are out of sync,
and so sometimes you get light, and sometimes you get dark.
But, why the rolling effect?
Well for that,
we have to understand the rolling shutter in a camera.
Or in any modern camera.
Old film cameras don't do this,
obviously, they just expose a shot
every time a frame goes by.
But, no-no, not this.
THIS camera, and all modern cameras
run, a line at a time, scrolling down the screen.
Which means it can take a fraction of a second difference
for it to go from the top of the frame, to the bottom
And the result is this rolling effect.
Some of those lines are recorded when the light is fully on,
and some of those lines are recorded when the light is dim.
And that's the reason.
That's the reason you have this kind of weird, artificial,
rolling light problem,
when you're filming with an American device in Europe.
'Course the easy way to fix it,
would be for Apple just to have a 25 frames a second option,
but that would be far, far too difficult for them...
And THAT is something you might not have known.
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