I'm looking at getting a dome port for my Ikelite housing (Canon 400D and Sigma10-20mm). What advantages has the 8" port over a 6" port? The 6" is under half the price of
the 8" in NZ.
the 8" in NZ.
Dome ports
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Viz'art
Contributor
The larger radius of the 8" dome will help with corner sharpness and will allow over/under shots to be made much easier.
Dome port distribute light in a spherical pattern, the center of the rays need to be matched with the optical axis of the lens, lens are made to focus on a flat plane, hence the problem with really small dome such as 4" is the edge cannot be made to focus on the same plane as the center, the same is true of larger dome but because of the wider radius the rays are located further away and are easier to bring into focus, the moral of the story is the smaller a dome is, the harder it is to attain good result. Large dome are not exempt of side effect, they create a sizeable air space inside the housing and need to be weighted down sometime such as in your case with a lightweight housing.
Hope this help.
Jean Bruneau, Aquatica Technical Adviser
Dome port distribute light in a spherical pattern, the center of the rays need to be matched with the optical axis of the lens, lens are made to focus on a flat plane, hence the problem with really small dome such as 4" is the edge cannot be made to focus on the same plane as the center, the same is true of larger dome but because of the wider radius the rays are located further away and are easier to bring into focus, the moral of the story is the smaller a dome is, the harder it is to attain good result. Large dome are not exempt of side effect, they create a sizeable air space inside the housing and need to be weighted down sometime such as in your case with a lightweight housing.
Hope this help.
Jean Bruneau, Aquatica Technical Adviser
Nice post Viz'art, welcome to :sblogo:
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