Shooting Macro With A Curved Port

In this episode of the Underwater Photography Show, Matthew Sullivan and Alex Mustard discuss the use of curved macro ports for underwater photography, a topic they received a lot of questions about lately. While it’s not a common piece of gear, it offers some significant advantages that are worth exploring.

Typically, underwater photographers use a domed port for wide-angle shots and a flat port for macro photography. The curved port falls somewhere in the middle. While a few manufacturers like Nauticam and Subal have made these ports, they were not designed or promoted for macro lenses. Instead, they were intended for semi-wide lenses that are too wide for a flat port but don't require a large dome port. Essentially, a curved port is a narrow, macro-like port with a small section of a dome at the front. We've both found success by repurposing these ports for macro use. [1:40]

There are two primary reasons we recommend using a curved port for macro photography. The first is that it significantly improves image quality, especially with wider macro lenses. When a lens like a 50mm or 60mm full-frame equivalent is used behind a flat port, the image is sharp in the center but becomes slightly blurry towards the edges of the frame. This happens because the lens is looking out through the flat port at an angle, which introduces chromatic aberration. You can see this in your shots, such as where a white speck near the edge of the frame is not sharply defined, but has blurred edges in a rainbow of colors. While many photographers may not be concerned with this, a curved port can provide sharpness all the way to the corners of the frame, which is ideal for specific types of shooting. For example, if you want to capture a goby on a piece of coral and want the coral to be sharp across the entire frame, a curved port is an excellent solution. We've found that this benefit also allows us to shoot at wider apertures, like f/3.5 or f/4, without sacrificing image quality across the frame. [2:24]

The second major advantage is that a curved port provides a wider angle of view. When a lens is used with a flat port, the angle of view is reduced by about 30%. While a curved port won't give you the full 33% wider view of a perfect hemisphere dome, it does provide a significantly wider view, enough that it feels like you are using a different lens. This is a great benefit for travel, as you can get two macro lenses in one. Matthew often travels with his 60mm macro lens, a flat port, and a curved port to get this wider field of view. The wider field of view also allows you to get closer to your subjects while still fitting them in the frame. This is particularly useful in low-visibility conditions since you're shooting through less water. Getting closer also makes it much easier to light your subjects, as you can manipulate your flashes around the subject more effectively. [3:42]

For those interested in finding a curved port, there are a few options. While you won't find a port sold specifically as a "curved macro port," some manufacturers have made them for other purposes. We've both used old Subal ports, which can sometimes be found used on sites like Facebook. If you find one with a really long barrel, we recommend not buying it; a shorter one is better because it gives you space to add an adapter and port extensions. Nauticam also has an off-the-shelf option called the N100 4-inch port, which works well with a short port extension [12:42]. Another option is to use the glass from a Zen dome for the Olympus 7-9 to 18 lens, which can be found relatively cheaply on the used market [14:03]. However, it's important to note that a significant downside of curved ports is that they are not compatible with close-up diopters or wet lenses [13:21].

Ultimately, a curved port is a great tool for adding diversity to your macro portfolio. We like using it for larger, more static macro subjects like batfish, frogfish, seahorses, and octopus. It's a great solution for placing a subject in its environment and telling a broader story, especially since it allows you to get sharp image quality all the way to the corners of the frame. This opens up different compositional possibilities, like placing your subject in the bottom corner of the frame without losing sharpness. While it's not a widespread option, it does give your macro photography a real edge and allows you to have more fun shooting subjects you may have photographed a thousand times before.

To watch the full episode and get all the nitty gritty, check out the show below.