"Red Dot" means it's coated, the earlier (1904 to mid/late 1940s) were not coated. There were some coated Artars without the dot, too. With 6 internal surfaces, they need coatings. A coated Artar is very sharp, has excellent tonality, and is apochromatically corrected - meaning it brings the three colors red, green, and blue to the same plane of focus. They were made in focal lengths up to 70". But, they're slow and cover less than many other lenses, Goerz said that an 8 1/4" was the shortest to cover 4x5, and that without movements.
Originally Posted by ntenny