I Tremble For Our Children
EDITORS' CHOICE, SCHOOL | RIGHT | MARCH 18, 2008
(A teacher calls me to her classroom. She is trying to project an image on a screen behind a student for a TV camera shot with the projector at eye level in front of the student.)
Teacher: “There is a shadow behind the student now. How can I get rid of that?”
Me: “You can’t. He is blocking the light from the projector from getting to the screen. You could put the projector behind the student, but the image would be smaller on the screen.”
Teacher: “Then what can we do?”
(I get the idea of holding a piece of paper over part of the lens of the projector to create a square area where the student stands where no light would shine. This gives the shadow a bit neater of a shape rather than a human shape.)
Me: “Here, hold this paper over the left side of the lens where the student is standing.”
(The teacher puts a piece of paper RIGHT IN FRONT of the students face.)
Me: “No, right by the lens so a square unlit area will be where the student is standing.”
(The teacher moves the piece of paper and puts it directly BEHIND the students head.)
Me: “No, here…”
(I put the piece of paper in front of the projector lens, leaving a nice square dark area on the screen where the student would stand.)
Teacher: “Well now there is a square there! There is no image directly behind the student, just around the student!”
Me: “Yeah, I know. There is nothing you can do about that, though. It’s the physics of light.”
Teacher: “What if I ask your boss? Think he could do it?”
Me: “No, he cannot bend light around objects.”
Teacher: “Why not?”
Me: “Because he’s not a black hole.”
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