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PROFESSOR: --is that for objects that
look the same size in the camera,
the angle between a line of sight
along one edge of the object and a line of sight
along the other edge of the object
is always the same angle.
[INAUDIBLE],, could you grab me one of those big kick balls?
This is useful, because if we know that things in the camera
look the same size they're always the same angle, that
allows us, like you guys just did,
to predict where we'd need to put this in order
for it to look the same size.
All we have to do is extend these lines out a little bit
until the width between the lines
gets to be large enough to accommodate the object.
If you stand on your tiptoes and look if I put the object there,
well, obviously the edges of the object
are outside of my lines of sight.
Whoops.
Uh-oh, could you pull that back?
Whereas if I go further back to right
about here, if I extend this line of sight that way
and if I extend that line of sight there, right about here
the line of sight is going to be about the same angle
for this object.
So this is why astronomers and people who do image science
call this thing, this width of the object in the image,
they actually call it the angular width.
It's the angular width, because it's the angle
that the object takes up.
If we had a different object that was larger,
it would have a different angular width.
So we have this idea of, in our case,
we're not going to call it the width
of the object in the image anymore,
although that's what it is.
But we're going to call it the angular width, because we're
really not measuring a distance, we're measuring an angle.
Because if we measured a distance,
we'd actually measure the width of this
and we'd come up with this column.