Drop-in Filters and Adapters

Drop-in photographic filters came in a series of sizes that had been standardized by Eastman Kodak Company. Most medium format or miniature still cameras used Series V filters that were 1-3/16" (about 30mm) in diameter or Series VI filters that were 1-5/8" (about 41mm) diameter. There were larger sizes mainly for use with large format cameras, and some of the larger sizes are still manufactured. Series V and VI filters are no longer made, but are plentiful second hand. Many lenses took drop-in filters without needing an adapter, but in most cases the photographer used an adapter to fit the filter to the lens. The adapters used threaded inserts to hold the filters in place. Other accessories included auxiliary lenses, threaded retainer rings, lens hoods, holders for unmounted gelatin filters, and step-up rings. Threaded retainer rings were used to stack filters and auxiliary lenses. For example you could use a retainer ring to have a polarizing filter in combination with a close-up lens. Step-up rings were used to fit a larger filter on a smaller adapter, for example a Series V to Series VI step-up ring would be used to fit a Series VI filter or lens hood on a Series V adapter. Adapters were either push-on ones that slipped onto the lens barrel or screw-in ones that fit the threads inside the front of the lens. Kodak push-on adapters were called out by the outside diameter of the lens they would fit. Kodak screw-in adapters had arbitrary numbers that did not necessarily correspond to the thread size. For example, a Kodak No. 55 adapter fit a 28.4 mm diameter thread. You could get filters and adapters from Eastman Kodak, Ednalite, Enteco, Tiffen and others in the US. Tiffen still makes photographic filters. Drop-in filters went out of fashion for still cameras about 1970. Most recent filters screw into the front of the lens. Large drop in filters are still used on Hollywood motion picture cameras.

An adapter ring, a glass filter and a lens hood.