I appears from some of the above posts that you have a few misunderstandings about the port systems for the 9-18mm Olympus M43 zoom lens.
Nauticam only has one port recommended for this lens, the four inch Nautican port.
Regarding ZEN Underwater ports, NO adapter is made for mounting the ZEN PEN ports to the Nauticam Mini housings. A ZEN adapter is made for Subal type III ports like the 100mm for use with the Panasonic 8mm fisheye on the OMD and other Nauticam housings. These are coated optical glass ports and that it the reason someone might want to pay more. ZEN also makes a 170mm glass port for the Nauticam Mini mount for use with lenses like the Panasonic 7-14,12-35 and Olympus 12 F/2.
ZEN also makes an adapter for mounting the ZEN PEN PORTS to the Olympus housing for the EM5 and a 100mm port that mounts direct to the housing for the 8mm fisheye and all are glass.
Regarding the ZEN ports on the Olympus housings the 9-18zoom port works quite well and does not vignette even at 9mm. The port charts above are wrong, first the lens is 100 degrees on the wide end not 62 degrees and lens placement is not correct and acts like a flat port not a dome.
For more info. Regarding the ZEN PORTS I suggest you go to ZENunderwater.com and do some research. Also checkout my photos in the gallery all of which were taken with the 9-18 zoom and the zen-100 port most at the 9mm end of the lens.
Edited by Phil Rudin, 18 June 2013 - 11:06 AM.