0 out of 10 points and recommended
"As a micro four thirds camera, the EP-1 produces a 2x ''crop factor,'' meaning lenses used with it provide an effective field of view that is double their listed focal length. So in this case, the 50mm ƒ/1.8 operates effectively as a 100mm ƒ/1.8 lens."reviewed March 11th, 2010
Not quite true.
On the E-P1 the effective field of view is HALF that of the lens if it were on a full-frame camera, not double.
Put the other way, the FOV is that of a 100mm lens on a full frame camera.
The focal length does not change. If you could change the focal length by altering the size of the sensor or film, we wouldn't need lenses of varying focal lengths.