If you want to cast a large image at a short distance from the screen, either because the room itself is a little small or to minimize the bother of people getting in front of the projector and casting shadows, you’ll need a short-throw or ultra-short throw projector. There are no universally accepted definitions for what counts as “short” or "ultra-short," but most short-throw projectors can cast an image about 6.5 feet wide from 3 to 6 feet away, while ultra-short-throw projectors generally need less than a foot. By comparison, most projectors with standard throws need to be roughly 9 to 13 feet away from the screen for the same image size, and long-throw projectors have to be even farther away. The downsides of short-throw (and especially ultra-short-throw) projectors are that they are more expensive than traditional models with standard-throw lenses, and they are more likely to have noticeable variations in brightness or focus across the image. Ultra-short-throw models also require a particularly flat and stable screen. Even slight variations in the surface can distort the image and affect focus.