Below is an example of a spherical camera lens. The image below shows a studio lighting rig scene. The spherical camera can be used to convert this scene into a spherical HDRI that can be used with the skydome_light.
The image below is a render of the spherical camera in the center of the scene. The scene must be rendered at a high enough resolution and the pixel aspect ratio should be set to 1, otherwise, distortions may appear in the reflections of the scene.