Trying to Choose New Camera and Lenses: Olympus OM-D vs Sony NEX

Chris Noble wrote:

f-stop is a measure of light intensity. The formula is focal length divided by aperture diameter. It does not change when you change the size of the sensor that the lens is used with. If the two sensors have the same sensitivity, the exposure settings are identical regardless of their respective size.

What does change is the depth of field at the edge of the sensor frame. If the sensor is twice as big, you have to close down an additional f-stop to get the same depth of field at the sensor edge. I assume the OP is trying to compare depth of field and not lens brightness.