In video projection terminology, throw is the distance between a video projector lens and the screen on which it shines. It is given as a ratio (called throw ratio), which describes the relationship between the distance to the screen and the width of the screen (assuming the image is to fill the screen fully). Throw ratio is a characteristic of the lens of the projector (although "projector throw" and "lens throw" are often used synonymously). Some projectors (typically larger, more expensive ones) are able to accept a variety of lenses, while lower cost projectors tend to have a permanent lens that is not designed to be changed. Some lenses are fixed at a specific throw ratio, while most are adjustable (zoomable) to a range of throw ratios. Distance to the screen is measured from the front of the lens.