Flat or Domeport ???

A fiend of mine who is new to DSLR uw photo just got himself a Nikon D60 with the Sea & Sea RDX Housing. He got it with the standard flat port, which is used for the 18-55mm kit lens that came with the camera. On monday he is going to Cocos island and he has borrowed my Nikon 12-24mm lens, and then we were looking at ports for this combo.

Sea & Sea recommends using the RDX port base L plus the NX compact dome port and we tried that and it works fine, but just for fun I tried the lens with the RDX standard flat port. The lens fits nicely inside, I can focus close and far away and I can't see any difference in the pictures compared with the ones taken behind the domeport.

Now the question - He doesn't want to go ahead and buy the port base and domeport if he can manage with the flatport. We have only tried the different combinations on land.

Can anyone come up with a reason for buying the dome and base or should he just go ahead with the flat port ?

Kenneth

With a flat port the 12-24 will equate to 24-48 (*1.5 crop * 4/3). With a dome port 18-36 (only *1.5 crop). You really need to test in water - pool or even a large tub of water. Use something with fine detail (text or bar code works good) in the corners of the shot to evaluate sharpness. I would expect a vignette problem using a flat port. The 18-55 should really be used with a dome also. If corners are not sharp experiment with a diopter. I'm using a +4 on the 12-24 with my Nexus setup. The center of curvature of the port should be located at the nodal point of the lens. Just a mechanical fit won't necessarily work optically.

You will see the difference once you get underwater. Anything under an effective focal length of 35mm (the entire range of the 12-24 on DX) will exhibit increasing distortion and reduction in angle of view. The 12-24 shouldn't be used behind a flat port.

The 18-55 should be useful in Cocos but I agree that it should also be used with a dome port. If you are shooting fish portraits with the lens then a flat port is fine, but if you want to use the wide end a dome is better.

Can anyone come up with a reason for buying the dome and base or should he just go ahead with the flat port?

The reason: Physics (Optics).

I second what was said by craig & jcclink.

Sorry, but I have noticed a lot of questions like that from people with DSLRs. What's happening to UWPhoto courses?