-
Ok, @NicolasREMY you were totally spot on – I tested the port that designated to be used with Canon fisheye 8-15mm. The test was successful – no more vignetting effect, much better focus outcome.
Downside – the dom port is in very vulnurable position, when I am getting in and out of the water and need to put the camera down – the rig is unstable and putting at risk of bump (and de-sealing) or scratch either dom or viewfinder. I think I need to come up with some kind of cushion protection (may be chop the piece of pool noodle) to put underneath.
@MattD I got box of close-up lenses too – didn’t tried it yet. Will report on this later 🙂