The Canon G9 has a non-interchangeable zoom lens without threads for attaching filters. What? I thought … Yes, there are accessory lens and filters for the G9. These accessories are attached to a simple tubular adapter that fits over the lens as shown here. The G7 and G9 use the same adapter, Canon LA-DC58H. To attach the adapter, first remove the decorative ring which covers and protects the connection at the camera. The adapter has standard 58mm filter threads so anything that has 58mm threads can be attached (even a reversed lens!). Popular accessories are filters, especially polarizing filters , and lenses. Canon makes wide angle, telephoto and macro accessory lenses.
In addition to Canon, there are third party manufacturers for adapters, lenses and other accessories. One of the most popular is Lensmate. A U.S. company, Lensmate makes adapters for many different Canon cameras and also sells compatible lenses and filters to match its adapters. The Lensmate web site is an excellent source of information including comparisons of many different attachment lenses and filters: wide angle, telephoto and macro.
Shown above are the Canon and Lensmate adapters for the Canon G7/G9. The adapters are very similar except that the Canon adapter is made of hard plastic and the Lensmate adapter is made of anodized aluminium.
The Lensmate adapter comes with a protective end cap and can be ordered with a cover as shown here. Both the Canon and Lensmate adapters work very well and protect the lens while making the G9 even more versatile. I first used the Canon but now keep the Lensmate version in my bag after a filter got stuck on the Canon version. (The filter probably became stuck because of thermal expansion. Later, it unscrewed easily with no damage to filter or adapter.)
There is a wealth of information on the Lensmate website, including Richard Franiec’s line of accessories. Well worth checking out!