The port and extension ring puzzle in underwater photography
An underwater housing without the right port is a sealed tube you cannot use. The port is the piece that attaches to the front of the housing and holds the lens. Choose the wrong port and you either cannot mount the lens, get blurry edges (vignetting), or lose infinity focus.
Each housing manufacturer uses its own mounting system. Nauticam uses N120 (for large lenses) and N100 (for compact ones). Ikelite uses Dry Lock (DL), which locks with a quarter turn. Sea&Sea has its own threaded standard. Ports are not interchangeable between brands, even if the lens is the same.
The complexity comes from extension rings. Depending on your lens length, you need one or more rings between the housing and the port to position the lens correctly inside the port. A Canon RF 100mm macro in a Nauticam NA-R5 housing requires an N100 flat port with a 30mm extension. The same lens in an Ikelite housing uses a different DL port with a 25mm DL extension. Swap the rings and the lens either rubs against the glass or sits too far back for focus.
Our compatibility tool eliminates this manual research. Select your camera body, housing brand and lens. The tool displays the exact port, required extensions, and any restrictions (some zooms do not cover their full focal range in certain ports). It also flags combinations known to cause vignetting or mechanical contact issues.
Frequently asked questions
How do I know which port to use with my underwater housing?+
The port depends on three factors: your camera body, your housing brand, and the lens you want to use underwater. Our tool cross-references these three elements to recommend the right port.
Is a Nauticam port compatible with an Ikelite housing?+
No, each manufacturer uses its own port system. Nauticam uses the N120/N100 system, Ikelite uses DL (Dry Lock), and Sea&Sea has its own standard. Ports are not interchangeable between brands.
What is the difference between a flat port and a dome?+
A flat port is used for macro lenses and some zooms. A dome is needed for wide-angle lenses to correct underwater distortion. The choice depends on your lens.
Do I need an extension ring?+
It depends on the camera/lens combination. Some longer lenses require one or more extension rings to position correctly inside the port. Our tool indicates which rings are needed.