The Nikon Nikkor T ED 720mm f/16 is an ultra-long telephoto-design large format lens with a 210mm image circle. At 780g with a 67mm filter thread, it is surprisingly lightweight for its focal length. The f/16 maximum aperture means a very dim ground glass image, requiring bright conditions or a focusing loupe. The ED glass is essential for controlling chromatic aberration at this extreme focal length. A highly specialised optic for distant subjects on 4x5in.