Zoom Lens allows you to vary projection distance by adjusting the focal distance, which for this lens is 27.4 - 35.4mm. It has a zoom ratio of 1.3:1 and a standard-throw ratio that fluctuates depending on the aspect ratio of your projector. Installing a zoom lens affords greater flexibility. You can compensate for miscalculations during installation and by changing the projection distance with your zoom lens, it's possible to adjust your display proportions depending on class size or type of presentation.Throw Ratio- PT-DZ8700: 1.3–1.7:1- PT-DS8500: 1.4–1.8:1- PT-DW8300: 1.4–1.9:1