Docking Points and Large-Scale Entry Points
In the realm of underwater photography, the choice between dome and flat ports can significantly impact the quality of wide-angle shots. Here's why many photographers opt for dome ports:
Dome ports offer a wider field of view, counteracting the narrowing effect caused by refraction underwater. This means that a lens's underwater angle, which might be reduced to around 60° by a flat port, can be preserved or even restored with a dome port, maintaining the original wide-angle perspective.
Moreover, dome ports contribute to improved image quality and sharpness. They help maintain sharp corners and reduce vignetting, resulting in clearer, higher-quality images across the entire frame.
The handling of refraction and magnification is another key advantage of dome ports. By correcting distortion due to water refraction, they deliver a view closer to what would be seen topside, which is particularly beneficial for wide-angle lenses.
Dome ports also help minimize glare and flare underwater, with some featuring anti-reflection coatings. This can be a significant advantage when capturing vibrant underwater scenes.
Enhanced usability is another benefit of dome ports. They often allow close focusing and zooming without removing the port, offering flexibility during dynamic underwater shooting.
In contrast, flat ports are simpler but cause reduced field of view and image quality degradation due to water refraction. As a result, dome ports are preferred by many underwater photographers for wide-angle lenses where maintaining a broad, sharp perspective is crucial.
When it comes to macro lenses (greater than 35mm), they should be placed behind a flat port, as flat ports magnify images more than dome ports, allowing lenses to reach their true magnification potential.
A neoprene cover is recommended for dome ports, and fisheye lenses can do well in any size dome port, while rectilinear lenses need larger dome ports. The wider the lens, the wider the dome port should be.
However, wide-angle lenses may suffer from vignetting and chromatic aberration when used in a macro port. Not all photographers find a need for focus gears, such as with the Nikon 60mm and 105mm VR lenses.
Most wide-angle lenses require an extension with the dome port for optimal sharpness. Some photographers prefer to manually focus a macro lens for 1:1 or greater macro photography, requiring a custom focus gear for each lens.
The tokina 10-17mm requires a 15-20mm extension, and most other wide-angle lenses need a 40-60mm extension. Port extensions can be used instead of purchasing separate ports for different lenses, such as a 60mm and 105mm, to extend the port for the longer lens.
Small prime fisheye lenses like the Nikon 10.5mm, 16mm, and sigma 15mm usually don't need extensions. Using a macro lens in a dome port may result in vignetting and less magnification compared to a flat port.
Wide-angle lenses (less than 35mm) should be placed behind a dome port. Most dome ports are made of acrylic, but more expensive ones are made of glass. Glass ports offer sharper images and are more resistant to scratches, but scratches are permanent. Acrylic ports can be repaired with a mesh kit.
Any zoom lens requires a custom zoom gear, created by the housing manufacturer, for underwater zooming. When shooting macro behind a dome port, image quality is better due to less chromatic aberration, and magnification is 30% less, which can be useful for medium-sized fish or larger macro subjects.
Flat ports can introduce a small amount of chromatic aberration at the edges of the photo, more noticeable in wider lenses, but this can be corrected in photoshop. The price of custom zoom and focus gears can vary from $40 to $180.
Zoom lenses with a width less than 35mm at their widest point should be behind dome ports. When making a choice between dome and flat ports, considering the specific needs of your underwater photography setup can lead to significantly improved results.
