The Gates FP25 flat port contains a single, flat, uncorrected element. The field of view becomes narrowed underwater since the image is subject to the same magnification effect as a diver looking through a face mask.
A Flat Port allows full camera zoom capability. Diopters may be used to increase the magnification of macro subjects. +1, +2 and +4 diopters are commonly used, and available from Gates as an accessory kit.
This flat port contains a single optical acrylic element that is forgiving to minor bumps and handling, and it is field replaceable.