What is the purpose of a Dome?

Hello guys.

I'm very newbie in terms of underwater photography and videography, and I would like to know what is the purpose of a dome in the housing.

Is that to do a fisheye angle?

Cause I know that for fisheye angle shots you have a specific lens to do it (8-15mm)...

Thank you very much.

Hi Simão,

It is not just for fisheye but for wide angle in general. Because light diffracts differently on the water-glass and air-glass interface on both sides of the port, a flat port increases the apparent focal length. If you spend good money to buy a very wide angle lens it would be a waste to use a flat port. In contrast, for macro photography a flat port gives an extra boost in focal length and thus magnification.

If you asked to find out if you need to buy one or the other or both; for very wide angle a dome is probably a must to avoid vignetting but I personally don't care about wide angle and shoot anything from 24mm (35mm equiv) and up through a flat port. Perhaps not ideal but it works for me and I like lugging around only a single flat port. Others who are mostly into WA can chose to shoot macro through a dome port if they wish.

Bart

Dome ports allow you to shoot wide angle photographs more easily. You can use them with any lens but in general you want them for wider lenses both rectilinear ones and fisheyes. The dome is acting as a big optical element and it allows you to shoot a wide scene but of a "virtual image" that is created by the dome. The virtual image is between 1 and 15 inches from the dome (depending on the dome size, larger domes lead to virtual images further away).

http://scubageek.com/articles/wwwdome.htmlis a great tutorial on domes.

Bill

I think we are talking apples and elephants here. I thought the OP was asking about a dome port, not a dome diffuser for a strobe. Bill

Thank you very much guys!

Now I understood what's the use of a dome port.