PHIL RUDIN
Contributor
Burhan, I was realy hoping you would be able to answer that question yourself after reading the link.
Your question was "I don't see or understand how the flat port limits the FOV for the 12-50mm lens at all."
The answer is in the link and applies to ALL lenses at ALL focal lengths, not just the 12-50 zoom. When Wishn shoots the 12-50mm or the 9-18mm from behind the 4inch DOME the FOV remains as it is above water. So the 12mm end has an 84 degree AOV and the 50mm end has a 24 degree AOV. From behind the flat port things look bigger just the way they do behind your face mask. As a result they fill the frame more so the lens covers less when it is behind a flat port at the same given distance. The upside is that behind a DOME port you have a wider AOV at a given distance. The downside is that on the long end of the lens 50mm, or 43 macro setting you also get a wider AOV. This means that to get to the largest magnification you need to get much closer than you would behind a flat port.
On a flat port you have greater distance between lens and subject at closest focus distance at 50 or 43mm.
On the 12mm end of the lens behind the flat port you are going to need to backup to cover the same area being covered with the dome port.
I have attached another link, Welcome to zenunderwater.com! this one has pictures and may help you better understand the difference between the dome and the flat port both at the same focal lenght, 9mm and both at the same distance to the subject.
Phil Rudin
Your question was "I don't see or understand how the flat port limits the FOV for the 12-50mm lens at all."
The answer is in the link and applies to ALL lenses at ALL focal lengths, not just the 12-50 zoom. When Wishn shoots the 12-50mm or the 9-18mm from behind the 4inch DOME the FOV remains as it is above water. So the 12mm end has an 84 degree AOV and the 50mm end has a 24 degree AOV. From behind the flat port things look bigger just the way they do behind your face mask. As a result they fill the frame more so the lens covers less when it is behind a flat port at the same given distance. The upside is that behind a DOME port you have a wider AOV at a given distance. The downside is that on the long end of the lens 50mm, or 43 macro setting you also get a wider AOV. This means that to get to the largest magnification you need to get much closer than you would behind a flat port.
On a flat port you have greater distance between lens and subject at closest focus distance at 50 or 43mm.
On the 12mm end of the lens behind the flat port you are going to need to backup to cover the same area being covered with the dome port.
I have attached another link, Welcome to zenunderwater.com! this one has pictures and may help you better understand the difference between the dome and the flat port both at the same focal lenght, 9mm and both at the same distance to the subject.
Phil Rudin
