Viewport Free Camera
The free camera exists only in its viewport and is deleted when the viewport is closed. If you have marked a camera as the favorite camera 1 for a product, that camera's settings will be used to initialize the viewport's free camera when the product is loaded.
The free camera's settings can be modified in the Cameras editor. They are also edited as you navigate in the viewport.
You can change the sensor used by the free camera by dragging and dropping a new sensor onto the viewport or onto the Sensor field in the Cameras editor.