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Dome vs Flat Glass Ports from Outex Underwater Housing System



  • Domes make it better; Domes help correct aberrations that occur when light travels thru water as opposed to air.  Domes can deliver better results compared to flat ports, and also make it easier or possible some results that flat ports would not capture.
  • Size matters; Bigger domes are better than smaller domes, for a number of reasons.  The tradeoffs are; heavier, bulkier, pricier than smaller domes or  
  • Glass is optically superior; Glass domes are optically superior to plastic or acrylic, and they do not scratch as easily.  All of the Outex ports, including its domes, are American-made glass ports.
  • Universal fit protects your investment; Both Outex glass domes are designed to fit any/all lenses thru adaptors and clamps.  This design protects your investment and optimizes your usability and upgradeability over time.  Our domes support both threaded, unthreaded, hooded, curved, fisheye, etc.
  • Domes are ideal for split level and underwater use; While dome ports will not take anything away from your work above water, their impact or difference above the surface is irrelevant.  Domes are ideal for split level and underwater work.

For additional information explore other entries on our website on this subject.


Dome vs. Flat Glass Ports - General


In general, flat lenses are a great choice for capturing images that start and/or end above water. Today’s array of excellent variable zoom lenses also works well with flat Outex lenses since it gives the user a great range of choices in capturing above, split level, and underwater photos with a single lens, without having to exchange gear. Long lenses (greater than 24mm) also work well with flat lenses underwater in most conditions. The example below taken with a regular Outex flat lens illustrates this point.


Split level underwater photography using Outex Housings

Flat lenses are inexpensive, smaller, and lighter than dome ports, and they work well underwater, just as they do above water.  But light travels differently in water.  Underwater housings offer different solutions for underwater photography, and dome lenses are a great solution to accommodate the property differences between those mediums.  Outex is one of the only manufacturers offering glass ports (not plastic or acrylic), which is optically superior in both conditions.  Both flat and dome Outex lenses are made of imported, professional-grade glass.  And as most of the Outex underwater photography system, our lenses, both flat and domes, are modular and compatible with all of the housings/covers, and accessories.

All of the Outex flat lenses screw onto your lens filter thread (just like a UV filter or polarizer) and can work with any lens.  But some lenses, such as fisheye or hooded lenses do not have a filter thread.  Those require a dome lens, and Outex offers a series of adaptors and clamps that make our different dome sizes to be compatible with all lenses, both threaded or unthreaded (fisheye, hooded, etc.).   In other words, the Outex dome kits, like the rest of the system, grows with your needs/changes over time, and you only purchase what you need, and the rest of the system is compatible.  All covers work with all domes, lenses, etc.   And vice versa.

When it comes to quality, as with most photography, it's subjective.  In general, Dome lenses are better than flat for underwater, for a number of reasons explained in more detail below.  And those differences are especially pronounced for split level shots, or over/under photography.  See examples below by our Pros Paul Toma and John Starret.  The images below all use the Outex Dome 120mm.


Outex glass domes are the best for underwater split level photos 1

Outex glass domes are the best for underwater split level photos 2

Outex glass domes are the best for underwater split level photos 3


The perception that dome ports are better for underwater photography stems from unique optical qualities that flat lenses are unable to correct when shooting in water. There’s a great deal of detailed information about the differences between the dome and flat lenses, but our goal here is to pragmatically clarify the advantages and disadvantages of both so you can make an informed decision as to what’s better for your objectives, budget, and gear. There’s no question, however, that dome ports are superior for dedicated in-water use and split-level capture. Despite the higher price, size, and weight, dome ports offer significant advantages, especially for wide-angle lenses. And dome ports are the only Outex solution for many fisheye lenses that do not offer a filter thread. Thus, Outex designed dome ports that modularly work with most (if not all) fisheye lenses thru our custom clamps and adaptors, in addition to working with rectilinear (non-fisheye) lenses. That means you can use the same Outex dome port with multiple makes and models of lenses without having to buy a new/different dome port each time – just like the rest of the Outex system. And the Outex dome ports, like all of our lenses, are made of high-quality glass (not acrylic/plastic), and are compatible with all Outex kits and covers. 

Dome lenses are ideally suited for wide-angle lenses (less than 35mm), which in turn are ideal for underwater and split-level photography for several reasons. We’ll explain each in more detail below.  But in summary, dome lenses alleviate the differences between light traveling above and below water, while enhancing your camera and lens' ability to find focus and sharpness, especially for split level photography.

The improvements are gradual and vary based on camera, lens, conditions, and settings. but the two examples below show the differences we're illustrating below. Both images were taken with Canon 6D and 12-24mm f/4. The image on the left Dome 120mm, and on the right Dome 180mm.


Outex glass domes are the best for underwater split level photos 4

Outex glass domes are the best for underwater split level photos 5


Refraction; Image is not as magnified due to the refraction of light in the water. Refraction is the visual bending that results from the change in density and therefore changes in light speed as it crosses from air to water. Refraction occurs when the light changes speed when it enters a body of water, causing it to change direction. The subject becomes ¼ closer and 1/3 bigger. See the pencil image below.


Outex glass domes are the best for underwater split level photos 6

(Canon 16-35mm lens using Outex regular lens 82mm by Satiro Sodre)

Outex glass domes are the best for underwater split level photos 7

(Canon 15mm lens using Outex Dome 100mm by Julie Thies)

Outex glass domes are the best for underwater split level photos 8


Note again the excellent results with both the regular lens as well as the dome port photos above.

Sharpness; Improved color and sharpness retention since you’re closer to the subject (less distortion). Flat lenses create a progressive distortion away from the center of the image as they do not address the progressive refraction near the edges. That also means a dome port makes it easier to find focus throughout the frame. 

Aberration; Less chromatic aberration (color fringing), as the same refraction impacts not only light but as the light separates into the color spectrum’s component colors. Dome ports help correct light dissipation over distance, helping ensure a more evenly sharp, focused, and color-correct image.

Why the Dome? Dome ports help correct all of these problems. The angle of the lens helps compensate for the refraction of the water, as well as the color and sharpness distortions that go along with it as light travels thru each medium. The domes also increase the distance between the lens and surface of the water, therefore increasing the camera’s ability to find focus. 

There are a few drawbacks to dome ports, however. They cost more, as a result of the increased materials and much more complex manufacturing process. High-quality domes also have differing glass thickness in the center compared to the extremities. Domes are also a little bigger and heavier than flat lenses, so they are not as seamless to transport on your backpack as a regular optical lens. Outex domes are made of high optical quality glass, which also has inherent advantages over plastic/acrylic. Glass delivers superior clarity and will not scratch as easily. Outex dome ports come pre-packaged in a neoprene protective case to help store and protect them.

Outex glass domes are the best for underwater split level photos 9

Outex glass domes are the best for underwater split level photos 10

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