Alright so i've seen a couple of questions on fish eyes so I figured id throw down some stuff about them.
Fisheyes are lenses that give ultra-wide angles and barrel distortion.
Fisheyes normally consist of 3 parts: The shell, Inner Element, & Outter Element. The inner element helps widen out the shot and then the outter element help widen it even more and the outer element is were most of the barrel distortion comes from.
With fisheyes you will get something called vignetting or "vig". This is the black edging you see and this is caused by the shadowing of the multiple elements of glass in your lenses.
To figure out what type of lens you will need you need to check your cameras lens on the front and look for the little circle with a line through it and next to it will say your filter size.
(example: canon vixia series uses 43mm filter size so you would want normally a fisheye thats threaded for a 43mm.)
You dont "have" to get the same size lens as your camera although it helps reduce vignette and in some cases its a must when you are using a smaller size lens on a bigger camera.
Some people like to use say a 37mm fisheye on a camera with a 43mm filter what this does is it sometimes makes the barrel distortion greater. But to do this you need to have a step-down ring. With this though vig is increased.
Other methods of widening or making barrel distortion better is by using spacer rings. These are just rings that litterally space out the lens from the camera.
There are many different fisheye brands, they come in all different prices. The "major" brands now are:
Raynox:They make affordable lenses with decent glass quality. They are used alot on Sony VX's as a substitute for a century death lens since they are about 1/3 the price.
Opteka: They make affordable lenses with great lens quality as well and are very well priced. There a new company but have gotten ALOT of recognition in the past year. There most famous for there generic century optics "death lens".
Century Optics: They are pretty much the industry standard for fisheyes. They're glass quality is great, but they'll really hit you hard in your wallet.
Heres some tips for when filming with fisheyes or any other lens attachment:
-Turn steady shot off ( a must or your lens will appear to "move" in your shot )
-Don't keep the camera stationary with a fisheye.
-Try to stay close to your object your filming, but watch out for getting your camera hit
-Keep your lens clean, this is very important. Use a microfiber cloth, and not a t-shirt..the cotton in shirts is abrasive enough to cause scratches.
-Get creative and have fun
One more thing: Don't be lured into buying a fisheye just because it says its a "High Definition lens" There is no such thing, there only designed for HD 16:9, its a trick that many people fall into thinking that the glass they get it on there fisheye is "HD".
I ride 2 wheelers for stacks.