C Mount Fisheye Camera Lenses

How to Choose a Fisheye

Anyone who is deeply into photography is going to need a serious lens collection. The lens is the eye of the camera and determines what kind of pictures you can and cannot take.

What is a C-Mount?

One of the most important features of any camera is the lens mount. It connects the lens to the body and basically ensures that the lens is able to focus on the sensor so that you can actually get a clear picture. This means that the mount not only needs to hold the lens securely in place regardless of its weight, but also that it needs to hold it in exactly the right position. There are two dimensions that all lens mounts share; the flange back distance and the diameter. The first is the distance between the back of the lens and the sensor surface, while the second is self-evident. Consider the difference between the C-Mount and the very similar CS-Mount:

• C-Mount: This mount features a 17.53 mm flange back distance and 25.4 mm diameter. It aims for use with 16 mm film and is useful for cameras with small image sensors. You can add a 5 mm spacer to a CS-Mount camera to use a C-Mount lens but not the reverse.
• CS-Mount: This even smaller mount features a 12.53 mm flange back distance, and the same 25.4 mm diameter. It also features the same 1/32-inch thread.

What is a Fisheye Lens?

While many people are aware of at least some of the different lens types like a zoom, not everyone is as familiar with a fisheye lens. It's a form of extremely wide-angle lens that has a significant amount of distortion due to its near-spherical design. They are a form of prime lens, which means they have a fixed focal length as opposed to a zoom lens. They differ significantly from their more common siblings:

• Rectilinear Lens: The majority of camera lenses are rectilinear. This simply means that they show straight lines as straight.
• Fisheye Lens: These lenses produce a significant amount of distortion to the point that they show straight lines as curves under most circumstances.

When to Use a Fisheye Lens

Even though the name has nothing to do with it, fisheye lenses are an excellent choice for underwater photography. They work well in behind a dome port and provide clear focus at extreme closeups, which is a good thing when you're dealing with the very short sight lines underwater. It also helps that the apparent distortion is minimized since there aren't many straight lines in an underwater environment. You can also use them on land; they are particularly useful for vertigo shots.