Series filters

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Series filters are a type of lens filter made in several different sizes (or Series; see the table below). The filter Series were an attempt at standardization: the camera user could use the filter glass from the same Series on a range of similar sized lenses, needing only a different adapter for each lens.

Series filters are round glass or optical resin filters, usually in a metal mount distinguished by the absence of threads, or sometimes completely unmounted. The filter is mounted by placing it in an adapter. It is held in the adapter either by a threaded retaining ring or by a threaded lens hood that also functions as a retaining ring. The size of the "front" of the adapter is determined by the Series, but the size and style of the "back" of the adapter is chosen to suit a particular lens or camera. Adapters were made in many sizes and in both push-on and threaded configurations. Photographers could obtain an adapter for each lens, permitting one set of filters to be used on more than one camera. "Series to Series" adapters were used to fit larger series-sized filter to lenses of smaller diameter.

The sizes in the series filters are identified by a number. The number is usually in Roman numerals for integers and in Arabic numerals for half sizes. The series number is often stamped into the mount on their circumference. The original roman numeral sizes were measured in inches, but some manufacturers (such as Hasselblad) expressed Series VIII as "Series 63," its millimeter equivalent.

The diameter of the filter for each series is as shown in the table below.[1]

Series Diameter (inch) Diameter (mm)
IV 13/16 20.6
4.5 ~ 25.5
V 1 3/16 30.2
5.5 ~ 35.9
VI 1 5/8 41.3
VII 2 50.8
7.5 ~ 57.0
VIII 2 1/2 63.5
IX 3 1/4 82.6
X 4 1/2 114


  1. Warren, Bruce, 2001, Photography, Thomson Delmar Learning, ISBN 0766817776.