Short definition
Throw distance is the distance between a projector's lens and the projection surface. Throw ratio describes the relationship between throw distance and image width, and it's essential for planning any projection setup.
Detailed explanation
Throw ratio is one of the key planning figures for projector installations: it indicates how much distance a projector needs to produce an image of a given width. A throw ratio of 1.5:1 means 1.5 meters of distance per meter of image width — for a 4-meter screen, that's 6 meters of throw distance.
Projectors are categorized by throw ratio: long throw (above 2.0:1) for large distances with a small image, standard throw (1.3–2.0:1) for typical room depths, short throw (0.5–1.3:1), and ultra-short throw (below 0.5:1) for tight spaces. Many professional projectors support interchangeable lenses for different throw ratios. Lens shift is equally important, allowing the image to be repositioned without moving the projector itself.
Relevance in this field
Throw distance and throw ratio are fundamental parameters in every projection plan. Getting the calculation wrong leads to undersized images, keystone distortion, or shadowing issues.
Practical example
A conference room offers only 5 meters of depth for projection. With a standard-throw projector (1.8:1), the image would be just 2.8 meters wide. A short-throw lens (0.8:1) achieves a 6.25-meter-wide image at the same distance.
Related terms
Projector, front projection, rear projection, projection screen