What is the purpose of a viewfinder on a camera?

The purpose of a viewfinder on a camera is to display the field of view of the lens. It allows photographers to frame their shots by seeing what the lens sees, providing a preview of the composition before capturing the image. This tool is crucial for visualizing how elements in the scene will come together in the final photograph, helping to ensure that everything intended to be included in the frame is indeed captured.

In contrast, controlling exposure settings, adjusting focus manually, and showing the image after it is taken relate more to different functions within the camera. Exposure settings can be adjusted through the camera's controls, while focus adjustments can be managed by the lens's focus ring or through automatic focusing mechanisms. Displaying the captured image happens on the camera’s screen or through the viewfinder in certain digital models, but this involves reviewing a separate action from framing the shot.