Putting a polarizer on a Summitar lens once required a special swing-out mount with built-on hood, such as the early Leitz NY FISUM, or the later 13352, both of which clamped onto a 42mm front flange. While these filters were swung out they could be looked through and rotated to the required setting, and then swung back over the lens, the 180 degree rotation maintaining the same setting. But these old polarizers would be difficult to find now in usable shape, the old polarizers being prone to separation, even if once located. The more recent polarizer (introduced in 1998, Lager) was the Leitz 13356 which could be mounted on several lenses by means of one of three intermediate rings screwed into the E39 filter threads of lenses from 28 up to 50mm. But none of them could be used on the Summitar’s unique inset filter thread, so for some time it has been difficult to put a polarizer onto a Summitar.