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What does it really mean that telephoto lenses “flatten” scenes?

Why is depth of field affected by focal length?

Quick Question. When using telephoto lenses at say 200mm the DOF seems to be narrower. I've searched a little and every one mentions the same thing, that space is being compressed in the photo, therefore giving off a an out of focus background.

What does that mean? How does it effect DOF?

  • Not very clear to me. It seems to me you're asking two questions: what does "space is being compresssed" mean, and how space compression affects DOF. Is that correct? Please edit your question to make ik more clear. – Saaru Lindestøkke Jun 30 '12 at 13:32