What about the AV110 and the C-AF adapters?
What do I need them for?
The ewa-marine auto-focus adapter AV110 (included ex factory with all U-A, U-AX, U-AXP and U-AZ shipped) is bolted into the tripod mount of the camera and is used to maintain a predetermined distance between the camera body and the front port of the housing. The one end is bolted onto the camera and the clear poly-carbonate ring is clicked onto the outside of the inner frame of the front port.
The AV110 function is to ensure, that the water pressure cannot press against the lens. This is extremely important in the case of externally focusing lenses, as the pressure would change the preselected settings of the lens and stop operation of the autofocus. Unfortunately the AV also hinders you from adjusting lens settings( zoom etc.) while under water. These settings have to be preselected.
On the other hand, if you would like to make pictures above water or are only using fully internally focusing lenses, we can also recommend the ewa-marine C-AF-adapter set. (the C-AF is standard with all U-F... series housings as well as C-AF and C-AFX) The C-AF is used in place of the AV-110 and screws directly into the filter thread of the lens. It is the clicked directly into the front port. The special rotating ring allows the lens to turn while securely docked into the front port. In most cases, the zoom on externally focusing lenses can now be adjusted inside a housing of the U-A... series by gently pulling or pushing on the front port. (but only above water !)