balazer, (and everyone)
You are confusing two completely DIFFERENT things: Depth of Field, and Perspective.

DEPTH OF FIELD is what is defined by the entrance pupil, NOT Perspective.

Perspective is the way in which objects appear to the eye based on their spatial attributes; or their dimensions and the POSITION of the eye relative to the objects. http://en.wikipedia.org/wiki/Perspective_%28visual%29

Ptchaw said: "In terms of field of view, yes. In terms of depth compression, no."

No, that's WRONG,. "Depth Compression" is the same as "Perspective Distortion". In terms of BOTH FOV and depth compression, a 25mm lens on GH2 is the SAME as a 50mm lens on a 5D. IOnly in terms of Depth of Field, is it different. You still have to use the crop factor: A 25mm f/1.4 lens on GH2 is equivalent to a 50mm f/2.8 lens on Canon 5D.

Vitaliy already said it correctly:
"Lens does not define perspective. Your position and view direction define all such stuff.
Lens just crops (see FOV) and also adds small things like aberrations, etc."

Psyco November 15
"Isn't there anybody with a 5D MK2 and a GH1/2 willing to set up a simple shooting (some objects with controlled lightning)."

Yes. I have already done this. 25mm f/1.4 / GH2 = 50mm f/2.8 5D.

Here is the proof:
http://www.flickr.com/photos/siggystardust/sets/72157628086875568/

So please stop spreading these Internet myths about crop factor.

The entrance pupil distance compared to the sensor plane, or lens front, is really only going to show any significant difference at very close distances, such as with macro. It really is splitting hairs.