Usage and crop factors

A port is an optical interface between the lens and the water. Ports must be perfectly aligned to the lens to ensure a perfect image.

We have a range of ports on offer for underwater camera housings and professional underwater video housings. They vary both in length and type of pane, depending on the lens being used. The crop factor also has to be taken into account, and hence the categories of full format sensors below:

Crop FaktorSensortypDiagonale
2entsp. Four Third21,3 mm
1,6entsp. APS-C27,1 mm
1,5entsp. APS-C28,3 mm
1,3entsp. APS-H33,5 mm
1Kleinbild-Vollformat43,3 mm


Flat ports are used for a focal length from about 28 mm (full frame) and larger, and are typical of the standard 18-55 (APS-C), 28-80 mm, or 14-42 four-thirds format lenses.

They are available in different lengths and can also be used on macro ports. For each lens type, we have a special solution macro port with M67 thread.

If flat ports are used on wide angle lenses with a focal length of less than 28 mm, peripheral blur will result.

Compact Domeports


Compact dome ports are used for a focal length of 20-24 mm (full frame). Likewise, focal lengths lower than this will result in peripheral blur. The domed pane of the compact dome ports is made from PMMA and small scratches can simply be polished off again. These ports are matched to the length of the lens.


Fisheye ports are used for focal lengths of 20mm; in the 20-24mm range corner sharpness will be improved, whilst peripheral blur could occur if the focal length is greater than 28mm.

Fisheye ports are available in either PMMA or glass. The glass ports produce a better image quality, but cannot be used once scratched.

PMMA ports can be restored to usable condition again after polishing and have the advantage of being lightweight.

Distance ring

In order to save space and weight when travelling, distance rings can be used.

They can be used on various lenses, and the photographer does not need two different ports, but rather can simply lengthen or shorten the port for each lens.

Thus a port is used for the first lens, and the second lens is made up of the port and the distance ring (port extension) used together.

Accessories for Ports

Neoprene and protective covers

Various neoprene covers are available to protect the glass of ports. Neoprene covers protect against dust, and prevent cracking of the pane during transport.

The port opening can be closed using this protective cover. It protects the interior side of the glass. This is particularly important with fisheye ports, as they are very difficult to clean inside because of their shape.

Zoom rings

Zoom rings can be used to operate the zoom of the lens under water. A gear ring can be slid onto the lens and clamped on to the zoom. The gear connects to the operating unit in the underwater housing.

Various zoom rings are available for different lenses and underwater housings. For each camera the options are Z72, Z80 and Z90.

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