BRIAN SCHMIDT: So, that is-- it's a much, much worse problem than even
what I see as being a pretty scary movie already.
PAUL FRANCIS: Yeah.
So we really have to understand what it is
that makes it so hard to see faint things near bright things,
so we can do something about it.
So I mean, here is the camera I used to take that scary movie.
BRIAN SCHMIDT: I'm a Nikon man, myself, Paul.
PAUL FRANCIS: And basically, this consists of a lens and a detector.
Any Canon engineers in the audience will lynch me for that.
There are a few more things in the middle here,
but want can simplify it as this.
What you could imagine is, you've got light rays coming from different angles
here, like the red and the white, and they'll
be brought to focus at different points on the detector.
BRIAN SCHMIDT: So the different angles map
onto a different place of the detector, and we should see things.
So that doesn't really explain what's going wrong.
PAUL FRANCIS: Yup.
So here's a still frame from the scary movie.
And you can see, this is when the light was not too bright,
you can see the candle over here, and you can see the light.
And indeed, the headlight is there.
The candle is there.
They're landed on quite separate parts of the detector, so all is good.
BRIAN SCHMIDT: Yes.
PAUL FRANCIS: But now when you increase the light by a bit more,
still, that light's coming from here and that's coming from there,
but you'll begin to see that not all the light's coming in there.
For example, look up there.
No light's there in either situation, but if you go back, it's quite dark.
There, it's quite bright.
BRIAN SCHMIDT: And that's presumably not because the light
is being misdirected now.
It's just that there's so much light that we're seeing light
where it was not so obvious before.
PAUL FRANCIS: Yeah.
And if you go later still, you can see that the light from over here,
and from over there is, you know, like up there.
Go back a bit, there was no light up there.
Where's that come from?
And even more, later on, still.
Now it's impossible to see anything else.
BRIAN SCHMIDT: So, Paul.
People always like when I'm out showing them
the skies, talk about the magnification of our telescopes.
And so you might be tempted to think you can solve this problem just
by raising the magnification from your Canon to a big telescope.
PAUL FRANCIS: Yeah.
Well, let's go through and look at exactly where
the light's coming, which will explain why the magnification isn't
going to help you.
So here's our image when it's not too bright,
and we can turn that into a map of the brightness on the pixels.
So here's a map of that.
So you can see there's a lot of counts coming in these pixels over here.
That's the main headlight.
There's the lower headlight.
Over there is the candle.
And they're well, separate, but you can see there's not a sharp edge here.
You're getting the light from the headlight,
but it doesn't drop to 0 suddenly at the edge of the headlight.
It sort of slants off gradually.
As you ramp up the brightness a bit higher,
you can now see it's slanting off very gradually.
BRIAN SCHMIDT: So the candle's just barely visible now.
PAUL FRANCIS: Yeah.
So the light, and if you make it brighter, still.
BRIAN SCHMIDT: So if we magnify in on that,
we're just going to see the same thing everywhere.
PAUL FRANCIS: Yeah.
So the problem is, the light's not going where it's supposed to go.
So instead of the light going like this, some fraction of the light's
going elsewhere.
Not a very big fraction, but if this red light was incredibly bright,
even if 1 part in 100, or 1 part in 1,000, or 1 part in a million
that's going the wrong direction, it's still
going to swamp the rest of the stuff.
And if you magnify that-- let's take an image here, and you magnify it,
you're going to get a fainter, but equally blurry image.
You're not going to see anymore.
You're just going to make the same misdirected light
spread over more pixels.
That's not going to help you.
BRIAN SCHMIDT: OK.
So we need to think about how to get around this.
We have technology on our side.
Presumably, we can use that technology to solve this problem.