The throw ratio is a crucial parameter for projector lenses, determining the size of the projected image at a specific distance. The formula for calculating the throw ratio is:
Throw Ratio = Projection Distance ÷ Image Width
Where:
Projection Distance is the horizontal distance from the projector lens to the screen, typically measured in meters (m) or feet (ft).
Image Width is the width of the projected image, measured in the same units.
Calculation Methods and Examples
Calculating Throw Ratio with Known Projection Distance and Image Width
Suppose the projection distance is 3 meters and the image width is 2 meters. The throw ratio would be:
Throw Ratio = 3 ÷ 2 = 1.5:1.
Calculating Projection Distance with Known Throw Ratio and Image Width
If the throw ratio is 1.25:1 and the image width is 2.03 meters, the projection distance would be:
Projection Distance = Image Width × Throw Ratio = 2.03 × 1.25 = 2.54 meters.
Calculating Image Width with Known Throw Ratio and Projection Distance
If the throw ratio is 1.5:1 and the projection distance is 4.5 meters, the image width would be:
Image Width = Projection Distance ÷ Throw Ratio = 4.5 ÷ 1.5 = 3 meters.
Classification of Throw Ratios
Standard/Long-Throw Lenses: Typically have a throw ratio between 1.5 and 1.9.
Short-Throw Lenses: Have a throw ratio less than 1.
Ultra-Short-Throw Lenses: Have a throw ratio below 0.4.
Application Scenarios
Home Theater: Lenses with a throw ratio between 1.0 and 2.0 are recommended, suitable for image sizes between 80 and 120 inches.
Classrooms or Conference Rooms: Choose the throw ratio based on the available space; short-throw lenses are ideal for limited spaces.
By calculating the throw ratio, you can better select a projector lens that fits specific space requirements and optimize the projection quality.