Indeed there is a Euro version of the Nikonos connector – on the camera side it has 5 rigid pins rather than 3 rigid and 2 spring pins. The male ends have 5 holes to accept these pins, rather than the 3 holes and 2 flat contacts of the traditional Nikonos connector. Therefore the male Euro Nikonos (from the strobe) will fit any Nikonos female bulkhead on a camera housing – whether it be Euro or traditional Nikonos. However if you have a Euro Nikonos female bulkhead on your camera you will have a problem when you come to connect a traditional Nikonos cable as these will only take a Euro male connector.
For example if you use a Subtronic flash with Euro Nikonos cables it will connect to a housing with either a Euro or traditional style Nikonos bulkhead. However if you have a housing with European style Nikonos bulkheads on it and you try and connect a traditional Nikonos socket, for example a Sea and Sea cable – you can’t, because the rigid “Euro” pins will jam the connection.
S6 is a superior connection to the Nikonos and readily available on many European strobes such as Seacam and Subtronic. It uses 6 pins – which is required for Canon eTTL and also for Nikon iTTL operation if you want dual strobe iTTL compatibility.
There are 4 o-rings sealing the connector, as opposed to 1 on standard Nikonos cables (although the Euro Nikonos variant uses 3 o-rings)
The problem with S6 is that it will limit you to strobes with S6 cables. You can get traditional cables converted to S6 for a price, but if you are travelling light and your strobe breaks, you’ll find it difficult to just borrow somebody elses – as N5 is far more common.
If you are planning on using Subtronic or Seacam strobes exclusively and all your housings are S6 capable I would recommend S6. If you use strobes from other manufacturers then you will either need N5 or consider getting your cables converted.
Or you could go for a more creative solution as outlined in this thread:
http://wetpixel.com/forums/lofiversion/index.php/t14746.html
Theres some pics of both at the bottom of this page on the Seacam USA site:
http://seacamusa.com/products.shtml
Cheers
Steve