Outex Dome Ports: 120mm vs. 180mm — Which Should You Choose?
Mar 10, 2019
Outex makes two optical glass dome ports: the Dome 120mm and the Dome 180mm. Both work with any lens and any Outex cover. This guide explains the differences between them, how the adaptor and clamp system works, and how to choose the right dome for your shooting style.
For a full explanation of why dome ports outperform flat ports optically — including refraction correction, split-level performance, and sharpness — see the Dome Ports vs. Flat Ports guide.
120mm vs. 180mm: Quick Comparison
| Feature | Dome 120mm | Dome 180mm |
|---|---|---|
| Diameter | 120mm (~5 inches) | 180mm (~7 inches) |
| Best for | Travel, split-level, half over half underwater, uncontrolled environments | Professional, split-level, demanding conditions, controlled environments |
| Split-level performance | Good — requires more controlled variables (focal length, settings, lens) | Excellent — provides greater margin for variables and conditions regardless of settings, focal length, lens |
| Portability | More compact and travel-friendly (600 g, or 1.3 lbs) | Larger and heavier (1,700 g or 3.7 lbs) |
| Price | More affordable | Higher cost |
| Lens compatibility | All lenses via adaptors or clamps | All lenses via adaptors or clamps |
| Cover compatibility | All Outex covers | All Outex covers |
Which Dome Should You Choose?
Choose the Dome 180mm if:
- You shoot split-level (half above, half below water) frequently
- You want the widest margin for error across different lenses, focal lengths, and conditions
- Image quality consistency is the priority over portability
- You use very wide-angle lenses (below 16mm)
Choose the Dome 120mm if:
- You travel frequently and need a compact, lightweight kit
- You shoot general underwater work rather than split-level
- You want a more affordable entry point into dome port shooting
- You are comfortable working with more controlled shooting variables
The 120mm can achieve the same results as the 180mm — it simply requires more precise control over variables like focal length, proximity to subject, lighting, and composition. The 180mm makes it easier to get the shot across a wider range of conditions, especially for split-level work.
How the Adaptor and Clamp System Works
Both Outex domes are universally compatible with any lens — past, present, or future — via two attachment methods:
- Dome adaptors — for lenses with filter threads. The adaptor matches your lens filter thread size (all standard sizes supported) and positions the dome optimally around the lens, just as a flat port would thread on.
- Dome clamps — for lenses without filter threads (fisheye, hooded, curved-front lenses). The clamp anchors to the lens body and connects to the dome, optimising optical placement and adding a stability anchor point inside the cover.
The two domes use different adaptors and clamps, each engineered to optimise optics and usability for that dome size. As your lens collection grows, you simply add the relevant adaptor or clamp from the Parts page — the dome itself remains compatible.
Unlike rigid housings where the lens floats inside a fixed dome (risking vignetting and misalignment), Outex adaptors and clamps anchor the dome precisely to each lens, guaranteeing correct optical positioning every time.
Compatibility
- Both domes are compatible with all Outex cover sizes (Entry 100, Pro Regular 110, Pro Large 130).
- Both domes are interchangeable with all Outex flat ports and accessories.
- You can own both domes and switch between them depending on your shoot.
- Domes can be added to any existing Outex kit at any time.
How to Order
Dome kits (dome + adaptor or clamp) are available in the Accessories section. Individual domes, adaptors, and clamps are available separately in Parts.
Each kit includes one adaptor or clamp of your choice. If you are unsure which adaptor or clamp you need, specify your exact lens make and model when ordering — for example, "Canon EF 11-24mm f/4L USM" rather than just "24mm lens" — so we can confirm the correct fit. You can add further adaptors or clamps from Parts as your needs evolve.