hugh_scarlett

<p>The nikonos 15mm lens will never work behind a port, the lens optics are designed to work with the refractive indexes of water, the whole principal of using nikonos lenses is to them as wet lenses.<br>

<br />Since all the nikonos lenses were designed for film, the image circle conforms to a 36 x 24mm image frame which matches the Nikon D700 and D3 and gives an image circle of 43.27mm, if used on a DSLR with a sensor having a smaller frame there will always be a crop factor. A super 35 sensor on cameras such as the Sony NEX range is 23.6 x 13.3mm with an image circle of 27.1mm</p>

<p>Probably the ideal wet lens for adapting is the Sea & Sea 12mm which will provide a very wide image even considering the crop, also having access to the optics and framing of the close up kit and macro systems. With any adaption being able to have the option of going back to dry lenses and ports as well creates the ideal situation, one just can't change underwater, but that's the price of exceptional optics.</p>

<p>Hi Craig<br>

I am wondering where you got the Nikonos film plane flange distance of 28mm from. Measuring my Nikonos 4 & 5 with a set of electronic verniers produces a totally different dimension.<br>

From the front lens flange to the film plane, in this case the film pressure plate gives a dimension of 39.35mm Allowing for film thickness this would give a film plane distance of 39mm not 28mm.<br>

This is a significant difference when it comes to back focus and if a nikonos lens was set at a flange distance of 28mm everything would be out of focus according to lens focus settings, sure visual focusing on an LCD screen would overcome this, but you would get a significant loss in overall focusing range. If you tried to use macro tubes or a Nikonos Close Up kit, you would probably never get focus. 11mm difference is massive in optical distances.<br>

Hugh</p>