button. To resume autofocus, one releases the button. Some newer bodies allow these buttons to be assigned to perform other functions; for instance, the Canon EOS 7D allows the photographer to set these buttons to perform any of six functions. Focus preset: The focus preset feature is found on most super telephoto EF lenses. The focus preset feature uses one switch, one button, and one ring. It is used for presetting a given focus distance into memory, so that the photographer can quickly recall the focus distance, without the need for autofocus. The switch has three settings "off"( o ), "on"( | ), or "on with sound"( ((- ), and is used for turning on the feature, and deciding if sound is desired. The "set" button is used for saving the focus distance into memory. The focus preset ring is used for recalling the memory save point. It is a thin knurled ring, usually located in front of the Focusing ring. To use this feature, one must set the switch to either "on" or "on with sound", focus the lens to the desired distance, then press the "set" button. After this, when the feature is turned on, the photographer can turn the focus preset ring, and the lens will recall and focus quickly to the distance that was saved. This feature is useful for sports and birding photography (for instance, to allow rapid focusing on the goal or on a spot where the birds may perch). Filter mounting: This mount is used for attaching filters to EF lenses. There are three types: front threaded mount, inner drop-in mount, and rear gelatin holders. Front threaded filters are used on most lenses, and are attached by threading and tightening the filter. Inner, drop-in filter mounts are used on super telephoto EF lenses. They are attached by first pressing the two buttons on the filter mount, and pulling it out. Then either a round threaded filter is attached, or one can use a gelatin filter. Rear gelatin filter holders are used by cutting out a sheet of gelatin, to the size shown on the back of the lens and then sliding it into the holder. Filter mounts are useful for all types of photography, and every EF lens has either one or two of the three types used. Lens hood mount: This feature is found on most EF lenses. This mount is used