As advertised
Lens is very good. If you look through the lens compared with the standard lens of my camera you clearly see the bigger lensopening due to the lower F1.5 (bigger diaphragm). The included lock ring is a very usefull idea. When I mounted it on the camera I wasn't able to close the housing, I was short of less than a millimeter. Size of starlight lens corresponds to the drawing and the lenses look about the same size (but of course the back focal lenght can also differ a bit). I have to figure out how to adapt the camerahousing a bit to accommodate this lens. Worth buying ? Yes for sure.