What is a "Port"?
The SLR port is the cylindrical shape front of the housing that contains the camera lens. The port removes easily and is available in various lengths to accommodate different lenses. A dome front is recommended for (35mm film equivalent) lenses 28mm and wider, and a flat front for macro and longer focal lengths.
The seal of the Ikelite port system is the only design that allows you to see if it is correct. You can look through the clear plastic and see the "O" ring seal. If it looks sealed it will be sealed. Every other SLR housing relies on theory and hope. There is no way to see if the port is sealed properly on an aluminum housing.
Selecting a Lens Port
Refer to the appropriate port chart based on the manufacturer of your lens. Ikelite SLR housings have a standardized distance between the camera body's lens mount and the housing's port mount. Port recommendations will fit a specific lens regardless of the camera model it is attached to.
Lenses are listed in numerical order. Make note of the specific lens designation. For example, a newer image stabilized lens may not fit in the same port as an older non-stabilized lens.
Port charts by lens manufacturer:
Using an accurate method of measurement, such as digital calipers, measure the lens diameter at its largest point. The lens must be less than 3.3" (83mm) at its largest point to fit in Ikelite ports. Measure the fully extended length of your lens from the attachment point on the camera body. Proceed to either the Standard Port System or Modular Port System to locate a lens long enough to accommodate your lens. Differences between the two port systems are summarized below.
A lens must focus to at least 12" (30cm) to be used underwater behind a dome port. If your lens does not focus to at least 12", a +4 close-up lens must be added to the front of your lens and included in the overall length measurement.
Telephoto zoom and telephoto macro lenses with a focal length beyond 105mm are not recommended for use underwater.
The Modular Port System allows you to build a dome or flat port out of universal components. The interchangeable port bodies and extensions combine to create endless combinations for maximum versatility and performance.