Hi,
As it is my first post let me first say hello from Poland 
I shoot photos with Canon 300D + 10-22mm in Sea&Sea housing with NX Compact Dome Port (174mm/7inch). Mainly I'm interested in WA shots of wrecks and caves. So far I have used AF but in Baltic Sea and in caves it's quite problematic. I have to focus on buddies lights or use my light to illuminate objects. I thought that manual focus could be an option.
I found some information that virtual image apperas in distance of 2D where D is dome diameter. On this forum I found link to article http://www.scubageek.com/articles/wwwprim.html where author says that according to rule-of-thumb it should be 3x radius minus 4x thcknesses of the dome, this will be less than 2xD. What is correct? Is idea of 2D big simplification?
Does anybody use lens 10-22mm with S&S NX Compact Dome Port and shoot photos with manual focus? If yes, what distance do you set on lens?
Beside, I have tried to set 2xD distance on my lens, but when I put an object 34,8cm from the camera and used AF it set lens in distance bigger then 40,0cm (something between 40 and 100cm). Do you know why it happened like that? How to set 34,8 cm properly?
Sorry for such a long question.
Best Regards
Leszek
