A Hudson blog:
Series filters are a type of lens filter that were used by photographers from the 1920s into the 1960s. The filters were an attempt at standardization where a single size of filter could be used on lenses from various manufacturers. While most series filters are no longer produced, some larger sizes are still produced for cine lenses.
Series filters are round glass (or resin) filters that are usually in a metal mount. While they look similar to modern filters, the metal mounts typically have no threads. The filter is used by placing it in an adapter that mounts on the lens. The filter is held in place either by a threaded retaining ring or by a threaded lens hood that functions as the retaining ring. The size of the front of the adapter will match to a specific size of series filter, while the rear of the adapter will mount on the lens of the camera. The adapter will either screw into the lens threads or slip over the lens collar.
For users of vintage cameras, a set of the same size series filters may require different adapters if different cameras are being used. The adapters can be found on eBay and at photographic swap meets.
The most common series filters that you might encounter range from series IV (filter size 20.3mm) to series 9 (filter size 82.6mm). Common manufacturers of these filters were Tiffen, Kodak, Ednalite and Enteco.
A very comprehensive source of information on series filters can be found at the website of Robert Allen Kautz Photography.
Comments