>>Hany Farid: This is a photograph of Lee Harvey Oswald.
It shows him carrying a gun, holstering a pistol,
and you can't see what's on the newspaper
but he's holding these Marxists or communist newspapers.
And the photograph is very damning.
First of all, it showed that he had weapons and it also sort
of list further evidence
of his communist sympathies at the time.
And if this photograph is fake, it would almost certainly point
to a broader conspiracy because that means the police doctored a
photograph to try to spin a story.
And the thing that has people really bothered
about this photograph primarily is the lightning
and the shadows.
So if you look at the cast shadow by his body,
you see easy going back and to his right which would suggest
that the light is sort of relatively low
because the long shadow and off to his left
that would sort of give rise to that.
Now what I'm showing you here is a magnified view of his face.
And you see this very long shadow being cast by his nose
and that would suggest that the light is above him.
And I have to say when I first looked
at this it seemed weird to me.
I was like how did that happen?
So I thought I wonder if this is really a fake image.
Now at the same time we had been doing a study to try
to understand the limitations of the visual system and reasoning
about shadows and lighting and 3-D geometry.
And it turns out we are spectacularly bad at it.
I mean really it's unbelievable how bad we are so I was able
to temper my suspicions a little bit with an understanding
that my brain just isn't very good this so I wanted
to really not just do a qualitative study.
I really wanted to sort of get at this
at a very quantitative and mathematical way.
And fortunately there's just now enough technology
that we're able to go back and look at this photograph
from 1962 to try to answer this question.
If we're interested in reasoning about shadows,
the first thing we have to realize
that everything here is happening
in a three dimensional world.
We're looking at a two dimensional image
but everything here happened in the world.
And if we want to re-create this, we need 3-D models
of everything so we can figure
out well I'll put the light here, and the camera here,
and the person here where does all [
indiscernible] so we have to build 3-D models.
So the first challenge is his head.
So this is on the top a mug shot of Oswald,
so profile and frontal view.
And what I'm showing you here are the corresponding views
of my 3-D model.
So we now have a 3-D model.
The most important thing
of course here is not every little tiny detail
but it's the size of his nose because that's eventual is going
to cause the shadow that we care about.
So you can see that the shape of the nose is about right.
So now, we need a 3-D model of the body and maybe a little bit
of the scene around them.
More or less, we now know where Oswald was standing relative
to the camera and more importantly where was the light
because we now know where the light would have
to be to cast that shadow.
So now, the interesting question is what does his face looked
like because if this is actually a composite and the shadows
on the face will be inconsistent.
So here's the original, and here's the model
for the previous scene, and there's all kinds
of interesting things here.
So first of all, look inside the wells
of the eyes you see the same type of darkness.
Under the lower lid, you see the darkness from the shadow.
Of course, the nose is almost perfect.
There's that very long shadow
which is really surprising by the way.
And my favorite part, which is on the neck,
you see the shadows cutting in like exactly like you have here.
So everything in this photograph is exactly consistence
so you can build a quantitative three-dimensional model
of the scene, of the person, of the head and figure
out where the camera and the light was, reconstruct
and everything is perfect.
So if this was a fake, it would have been almost unimaginable
how they could have done this in 1963 because there's lighting
in the shadows from the person,
from the beam would have been exactly right
which even today would have been extremely hard to do.
So it's almost certainly the case
that the reason why people think this is a fake is simply a
failing of the visual system to reason about 3-D lighting
and 3-D geometry because in fact
when you do the reconstruction everything is a hundred
percent perfect.
>>Hany Farid: You know you tend to think about digital forensics
as this modern day tool answering modern day problems.
But the reality is because photo manipulation does have a long
history, we now have sufficiently powerful tools
where we can now start going back through history and trying
to answer some really interesting long-standing
mysteries throughout history and that's sort
of an exciting new avenue to use these modern day tools
to go back through the decades to try
to understand certain things.
I think if you were going to make claims
that something is fake,
you can't just say something looks wrong.
I mean that's sort of the whole point is that you got
to bring more rational reasoning to these types of things.
I think that's what these forensic tools can do.