Nikon Nikonos 15mm lens is an ultra-wide submersible lens. It can not be used on land. But, underwater, it has been long considered as the best underwater optics even before high resolution digital cameras become available. It featured modern retrofocal design, fast f/2.8 aperture and close focusing ability.
But the best feature about this lens was its rectilinear (non-distorting) design and incredible sharpness from corner to corner – something that even the best land lenses can not achieve when placed behind flat or dome ports.
It is because of these rectilinear properties that make this lens so highly desirable for cinema work. Unlike fisheye lenses and land lenses placed behind glass ports, the Nikonos 15mm produces perfectly flat images underwater. While this may not be such a big deal in still picture photography, motion pictures require undistorted images to create immersive feel. And, undistorted images are also a must in 3D stereoscopic cinematography. Any geometric lens distortion, whether created by a fisheye lens, flat or dome port, cause vertical disparities. Vertical disparities are when equivalent parts of the left image are shifted vertically in relation to the right image of the stereo pair. These are aberrations that our brains can not tolerate and can cause severe eye strain and even nausea by viewers watching stereoscopic 3D content that was filmed using lenses or ports with geometric distortions.
Our MTF (Modulation Transfer Function) measurements show that the Nikon Nikonos 15mm lens is a very sharp lens – so sharp it can out-resolve even the highest resolution digital sensors in use today. In fact, it is capable to resolve more than 8K – something very few land lenses can achieve on land – a truly remarkable optical performance. In comparison, a typical 9” optical glass dome port when coupled with an equivalent wide angle land lens can not resolve more than about 2K around the edges regardless of how good the taking lens is. In practice, much less than 2K. This is because of the so-called image plane curvature – an optical phenomenon causing flat image projected sharp on curved surface and therefore out of focus around the edges of a flat sensor.
A flat port performs even worse, causing geometric distortions, astigmatism and severe chromatic aberrations – typically resulting in less than 1K resolution in an equivalent setup.
The Nikon Nikonos 15mm lens is the only ultra-wide angle underwater optics that can produce undistorted ultra-high definition images.
No other submersible lenses or any other terrestrial lens placed behind an underwater port, can offer such performance. Even the newer RS Nikonos range of lenses do not offer ultra-wide angle rectilinear option and are limited to macro, medium angle and fisheye selection only, making them less attractive for general underwater cinematography.
So, what does this optical performance really mean in real-life pictures?
Here is an example of low light wide angle shot, captured at high frame rate With Nikonos 15mm lens set at f/2.8. (click on the image to see full resolution 5K version)
Pawel Achtel, B.Eng(Hons) M.Sc, December 2014