Underwater Photography Glossary

A dome port is a concentric glass or acrylic lens used for wide angle underwater photography and does not have the same refraction issues as a flat port, allowing for the same degree of coverage as the lens itself. A dome port creates a "virtual image", which is projected in front of the dome port and forces your lens to focus on the virtual image rather than the actual image. Dome ports come in various diameters, which must be matched to the specific lens used, sometimes requiring an extension ring that sits between the housing and the dome port.