Olympus FCON-P01 fish eye converter
The Olympus FCON-P01 fish eye converter is one of three front-fitting conversion lenses developed by Olympus for selected m.Zuiko Micro Four Thirds lenses. As its name implies, the fish eye converter produces a characteristic extra wide angle view which is heavily distorted, progressively more so towards the corners of the frame.
When fitted to a 14-42mm f/3.5-5.6 II Olympus m.Zuiko zoomed to its widest setting (14mm) the FCON conversion lens changes the focal length to an apparent 10.4mm (35mm Equivalent Focal Length: 20.8mm) and the diagonal frame angle of view becomes 120 degrees. This is not as wide as a true fish eye lens, like the 8mm f/3.5 Panasonic Lumix G Fisheye or 8mm f/3.5 Fisheye Olympus Zuiko Digital ED, which cover 180 degrees corner-corner, but for effect alone the FCON delivers a convincing imitation of a true fish eye lens.
You can fit the the FCON-P01 fish eye converter to the 14-42mm f/3.5-5.6 II Olympus m.Zuiko, including the re-styled 'R' version. It is not compatible with the original 14-42mm f/3.5-5.6 Olympus m.Zuiko or any other m.Zuiko lenses.
An advantage of front-fitting conversion lenses is that there is no loss of maximum f-stop, which is usually the case with teleconverters and extension tubes that fit between the lens and the camera body.