Complex sentence: Barnett McFee Clinedinst, Sr. (circa 1836--1904) was an American photographer and inventor, known for having invented the viewfinder and the mirror-and-prism "reflex" arrangement for which the single-lens reflex camera is named.
Split into simpler sentences: Barnett McFee Clinedinst, Sr. (circa 1836--1904) was an American photographer and inventor. He invented the viewfinder and the mirror-and-prism "reflex" arrangement for which the single-lens reflex camera is named.