Large format lens

Photographic optics generally project a circular image behind that is only required to have acceptable correction of aberrations over the intended film/sensor diagonal with little room to spare.

Allowing the lens to be shifted and/or tilted from the sensor/film axis without vignetting in the corners opposite the movement requires a larger image circle.

Early lenses suffered from flare and low contrast, worsening as the number of lens-air interfaces increased.

The introduction of and improvements in anti-reflective coatings vastly reduced flare; some many-element lens designs which had been abandoned due to low contrast in spite of otherwise excellent performance became practical.

For small formats such as 35mm, extreme long focus lenses can be found, with focal lengths 5, 10, or even higher multiples of the image circle, however, such extreme lenses are not normal for large formats (unless we chose to consider astronomical telescopes as cameras, which is very valid, indeed see eg Schmitt cameras and astrographs) The term telephoto has become widely if loosely used for any long-focus lens, but a true telephoto lens is designed to be physically shorter* than a simple lens of that long focal length.