The Canon WC-DC58 Wide Angle Converter Lens converts the focal length of the Canon PowerShot G1 by about 0.8x to expand its wide-angle coverage from 34mm to 27.2mm wide angle. To use this lens, you must have the Canon LA-DC58 lens adapter (not included), which lets your PowerShot G1 accept 58mm threaded lenses and filters.
This is the magnifying factor of a lens. Macro lenses will often be described by their “magnification factor”. A lens with a 1:1 magnification factor produces a projected image on the sensor which is the same as the subject.
The individual pieces of glass that form the overall optical construction. Most lenses have between four and eleven elements to bend the light rays to ensure a perfectly formed image appears on the light sensitive surface, such as a film or CCD. The elements are arranged in groups and may be seen in specification sheets as, for example, 6 elements in 4 groups. That configuration may have two single elements and the other four grouped in pairs.