The sense and nonsense of fisheye cameras

A fisheye camera uses a wide-angle lens to visualize the surrounding area (360°).
The camera not only sees what’s in front, back, left and right of the camera, but also what’s underneath.
With just one camera, you can capture an entire environment.
How does this camera work and when does it make sense to use this type of camera? A fisheye lens is not something new.
A well-known example is the peephole in the front door of senior residences.
Through a wide-angle lens in a tube, you can not only see who is at the door, but you also have a view of the hallway, including the ceiling and floor.
The person right in front of the door is clearly visible, outside of that the image is becoming more and more distorted (‘warped’).

Action

The same type of lens as in the peephole has also been used in security cameras for some time now.
The camera is called a fisheye or 360° camera.
The camera itself is a more or less flat disc with the fisheye lens in the middle.
Behind it is the (single) CMOS chip that converts the visible light (including the people or objects that reflect the light) into an electronic signal.
That signal is then visualized on a screen or can be recorded; Just like a regular security camera.
With a fisheye camera you can identify people, but the angle is also large enough to see where people are coming and where they are going.
For example, in certain situations you can choose only one multifunctional fisheye camera, instead of a separate camera for identification with a camera for overview.

Positioning

A fisheye camera can be positioned in different ways.
Hanging from the ceiling, the camera visualizes the entire space from that point and, for example, the stairwell, the elevator, the porch and/or the corridor are fully viewed.
Public transport benefits greatly from the use of this camera.
If the camera hangs on the wall, it gives the same effect, but from the side.
If the camera is mounted upside down in a conference table, all the people at the table and around it are captured.

Eliminate Image Distortion

However, the image of a 360° camera is basically distorted.
Fortunately, in addition to all the technology for image enhancement, among other things, the camera also has an application that can correct the image, or ‘dewarp’.
This function is especially useful if you are going to zoom in digitally and still want to have people in the distorted part clearly visible.
Because you are now only recording a part of the total image, it is wiser to have the image corrected by the recorder.
The camera then sends the full 360° image to the recorder, which also records it as such.
Live and retrospective zooming in or moving through the image (via a joystick or the pan-and-tilt buttons) and the software in the recorder straightens the image if necessary.
Just like with a controllable PTZ camera, but without all the mechanics to rotate the camera.
And also much more compact and therefore more aesthetically pleasing.