What is a Television Camera?

Why television screen or computer screen appears shaking whenever seen through a camera?

• Whenever i see computer monitor or tv screen through a camera it appears shaking. I come to know that this is not due to the interference of waves. Because from the same distance screen appears normal when i see through my naked eyes. If you have an answer then plz let me know.

• Answer:

  The screen refreshes itself faster than the eye can detect. The camera samples the light that falls through its lens at a speed faster than the eye can detect. When one is pointed on the other, the the rate one refreshes doesn't exactly match and isn't in phase with the rate the other samples the pictures, it is like two mismatched gears trying to mesh. At the points they mesh, the picture gets through but at the points they don't, the picture doesn't get through. Just like gears alternately meshing and not meshing, we see the screen flicker from the camera in a regular pattern.