The Promaster is the first lens to start at 24mm and zoom all the way to 200mm. Chrome-plated brass mount plates and combination aluminum/composite lens barrels reduce weight while maintaining strength and durability.
Optically, it uses high quality optical glass multicoated lens elements. Two aspherical lens elements and one SD (super low dispersion) glass element are employed in the optical design to insure sharpness across the film plane. The aspherical elements are each molded as one piece of optical glass, rather than a resin laminated to a glass core.
An internal focusing mechanism gives this lens fast autofocus. The lens front does not rotate during focusing-a great advantage when a special effects filter such as a circular polarizer is used. Focus distance is indicated on the manual focus ring.
Like the rest of the lenses in the XLD series, The 24-200MM F/3.5-5.6 lens is what is commonly referred to as a parafocal lens, meaning when focus is achieved at a telephoto focal length, it is possible to zoom back to a wide angle and maintain focus on the subject.