New to the DSLR Game

Just a couple of questions regarding the general use of my DSLR. There appears to be enough room between my flat port on the housing and the Olympus 14-42mm kit lens I'm using to add a diopter. I take mostly fish portraits. Is there any advantage to a diopter in a flat port? Also, I wasn't too worried about dinging the small port on my P&S but I even had a port cover underwater for that. I've got a big port cover for the flat port on my camera but there's no keen way to attach a line to it to prevent me from losing it. I guess the other option is to never tie of the camera to the d-rings while diving. Any thoughts greatly appreciated!

Hi Gary,

The main advantage of a dioptre (behind a flat port) is that it will decrease the mimimum focus of your lens - allowing you to achieve higher reproduction ratios in your frame. The disadvantage is that it will decrease the maximum focus distance of your lens! This means that you may not be able to focus on distant objects.

The situation is different behind a dome port where a dioptre acts to counter act the optical effect of the dome in water and actually maintains the normal focus range of the lens.

Alex