The Red Sea is an excellent wide angle destination, with vibrant reefs, caves, pinnacles, walls, wrecks, schools and if you are lucky encounters with pelagics. And all this in clear waters, with not a cloud in the sky to quench the sunshine.
Most subjects here, lend themselves to fisheye photography and having dismissed the Nikon 16mm as less desirably to the more modern Sigma 15mm in my D3 review, I decided to put my views to the test by taking the Nikkor to the Red Sea. In reality, under most shooting situations, there is little to chose between them. Both are sharp and work very well behind Subal’s FE2 dome. I feel that the Nikon resists internal dome reflections better, while the Sigma is marginally sharper a focuses noticeably closer. On one occasion when I was shooting an attractive red anemone with the 16mm + teleconverter, I was frustrated to run against the minimum focus. I was pleased with those shots, nonetheless, but felt there was a possibility for something different if I had been able to get closer still. I was already very close.
As has been widely discussed on the Wetpixel forums perhaps the biggest loss of FX over DX is the inability to use the Tokina 10-17mm fisheye zoom, or to have a real alternative to this lens. This lens offers such a perfect range for underwater wide angle photography, that it is the most compelling reason that many have found to stick to DX. The Tokina 10-17mm on DX covers 180˚ to 100˚ corner to corner. Compare this to the 14-24mm and 17-35mm on FX, which give 114˚ and 104˚ at their widest, respectively, and you see that there is relatively little overlap in their angles of view. Furthermore, the FX options are both rectilinear lenses, which are harder to optimise behind domes.
On the D700 the Nikon 16mm or Sigma 15mm both match the Tokina’s coverage at the 10mm end on DX, and exceed its sharpness and lessen its tendencies chromatic aberration. 180 degree coverage is ideal for most reef wide angle in the Red Sea and for scenic work I did not miss the Tokina. But a prime fisheye can be a bit too wide for marine life. The Tokina can be zoomed in, the FX fisheyes cannot. I did use the Nikon 16mm mounted on a 1.5x teleconverter simply to reduce its coverage to about 100 degrees for certain subjects. This decision had to be made before a dive, but it gave me a wide angle option with excellent corner sharpness and only mild barrel distortion.