Lens attachments are an option with numerous uses. Normal working distances of the zoom systems is approximately 90mm. These lenses thread onto the bottom of the zoom system and can extend the working distance out to 350mm or pull it in as close as 35mm. The extending lenses (.75X, .5X, and .25X) decrease the overall magnification, and increase the field of view. The shortening lenses (1.5X, and 2.0X) increase the magnification and decrease the field of view. As the working distance goes from long to short, the "taking NA" of the system increases, resulting in an increase in resolving power.