When a film has a wide aspect ratio (as they almost all do) and a fullscreen transfer (4:3) is made, the only option is to select a portion of the image judged to be of the greatest important and remove the edges. The Telecine machine can be programmed to select the best part of each frame, which may involve moving the scan area or on shot.
The technique of reframing a picture to conform to a different aspect ratio by cropping parts of the picture.
A method of converting a widescreen presentation to an image within a 4:3 aspect ratio without black bars at the top and bottom of the picture. The camera moves back and forth (panning and scanning) in each scene to show only the most important parts of the image. Results in the left and/or right edges of the image being cut off.