What is throw ratio and what it is used for
Throw ratio is a dimensionless coefficient describing the relationship between the projection distance (from the lens to the screen) and the width of the projected image. The higher the throw ratio, the further from the screen the projector must stand to achieve the same image width. A low throw ratio allows the projector to be installed closer to the screen - which is critical for auditoriums with limited depth or for placement below a balcony.
Choosing the correct throw ratio (and corresponding lens) directly affects: the placement of the projection booth, the length of the support structure, the availability of sufficient throw distance, and the image offset ratio (lens shift). All these factors are interconnected - one change will cascade through the others.
How the calculator helps with lens selection
Our projection distance calculator clearly computes what throw ratio you need for the chosen auditorium parameters - screen width, projector-to-screen distance and screen format (flat/scope). It also displays which available lenses cover this value, eliminating the need to manually search through catalogues.
If the designer changes the projector position or screen width, the calculator immediately recalculates whether the selected lens is still suitable or whether a change is needed. This addresses one of the most common risks in cinema hall design - an incompatible screen and lens combination discovered only during installation.
Use our projection distance and throw ratio calculator and select the right lens for your auditorium.