In film school, I wanted to project a film of mine in portrait (vertical) orientation rather than landscape (horizontal) orientation. However, my film professor told me that the projector couldn't be tipped on its side; oil in parts of the projector would drip over the film and onto the light, possibly making it explode.

How did I rotate the projected image 90 degrees without tipping the film projector?

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I used 2 flat mirrors.


1 Answer 1


Here is a way I think would work.

Use a mirror at about a 45 degree angle in front of the projector that redirects the light up. Then use another one that intercept that projection at a 45 degree angle and redirect it to the left. The end image will be projected on the left of the projector, not in the front like usual.

  • $\begingroup$ Exactly! It took me months to figure that out. Nicely done! $\endgroup$ Feb 2, 2017 at 5:59
  • $\begingroup$ @CreatedByBrett thanks. I haven't had physics class for over 10 years, but I really like it. I had to close my eyes and imagine your smiley face drawing rebound on mirrors in my mind for a while before I got the correct directions XD $\endgroup$ Feb 2, 2017 at 6:03
  • $\begingroup$ @CreatedByBrett Oddly, took me just several seconds to solve this, even though other riddles around here seem impossible to me. $\endgroup$ Feb 2, 2017 at 21:17
  • $\begingroup$ @Baskakov_Dmitriy That's surprising! You must have exceptional spatial reasoning skills. $\endgroup$ Feb 2, 2017 at 22:16

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