Flange
A mounting flange is a metal threaded ring with several holes on the perimeter which are used to secure the flange to a lens board. It is permanently attached to the front of a lens board with screws. Flanges are frequently missing from their lenses. If you have multiple flanges for the same lens, you can fit them to several different brand lens boards and then easily switch the lens among the different cameras.
Retaining Ring
A retainer is similar to a flange except that it has no screw holes and is used like a “nut” in a “nut and bolt”; it holds the lens or shutter onto the board more or less permanently by screwing on from the back. Sometimes referred to as jam nuts, retainers often require a special tool to install or remove, so lenses mounted with them are not as easily interchanged as those using flanges.
Lens board with the flange (Red) | The lens board with the retaining ring (Blue) | The shutter (Green)
Metric Flanges and Retaining Rings
Imperial Flanges and Retaining Rings
Measuring Instructions
In most cases, the make and model of the shutter can help determine the stock flange that will fit. An accurate measuring of the diameter of the threads can be compared in our charts to help solve the remaining questions. This information only covers the stock flanges for shutters. Barrels and other adapters may require more detailed measurement to create. When making custom flanges it is best to have the lens on hand, but following these instructions will give you all references you need.