How to Calculate Projector Throw Ratio for a Curved Simulator Screen
Learn how screen radius, arc length, projector distance, image width and edge-blending overlap affect throw-ratio calculations for flight, driving and racing simulator systems.
What Is Projector Throw Ratio?
Throw ratio describes the relationship between projector distance and projected image width.
For example, if a projector is positioned 3 meters from its target image area and needs to create a 4-meter-wide image:
Why Curved Screens Are More Difficult
On a flat screen, the projection surface is essentially one plane. On a curved simulator screen, different parts of the image are located at different distances and angles from the projector.
Changing Distance
The center and edges may sit at different distances.
Projection Angle
Each channel may approach the screen differently.
Screen Curvature
Image width follows a curved physical surface.
Understand Arc Length and Chord Width
A curved simulator screen can be described using several different measurements. These should not be confused.
Arc Length
Distance measured along the curved screen surface.
Chord Width
Straight-line distance between two points on the arc.
Projected Image Width
Effective width that one projector must cover within its image channel.
Basic Curved-Screen Geometry
If screen radius and angle are known, the arc length can be calculated using:
The straight chord between two points on the curve is:
These measurements help describe the screen geometry, but projector throw ratio should still be based on the actual image coverage required by each projector channel.
Do Not Use Total Arc Length as Projector Image Width
This is one of the most common mistakes in curved-screen design.
The projector does not simply produce a flat image whose width equals the entire curved surface length. The projected image is optically transformed when it reaches the curved screen.
Step 1 — Measure the Curved Screen
Radius
Defines the curvature.
Arc Length
Total surface length.
Height
Defines vertical image size.
Viewing Angle
Defines required field of view.
Step 2 — Define the Number of Projector Channels
A small curved screen may use one projector, while wider panoramic simulators commonly use two, three or more channels.
1 Projector
Compact curved projection.
3 Projectors
Common panoramic simulator configuration.
Multi-Projector
Large FOV or complex simulation environments.
Step 3 — Calculate Each Channel Separately
In a three-projector panoramic system, calculate Projector A, B and C independently.
Projector A
Left screen section plus overlap.
Projector B
Center screen section plus two overlaps.
Projector C
Right screen section plus overlap.
Step 4 — Add the Edge-Blending Overlap
Two neighboring projectors normally share part of their images so the visible seam can be blended.
That overlap increases the physical image width required from each projector.
Step 5 — Measure Projection Distance Correctly
Projection distance is generally measured from the projector lens reference position to the target projection surface according to the manufacturer's lens specification.
On a curved screen, the physical distance varies across the image. For preliminary planning, use the projector's optical centerline toward its assigned screen zone, then verify the near and far edges.
Center Distance Is Only the Starting Point
A projector aimed toward the center of its channel may have one distance at the image center and slightly different distances toward the outer edges.
Near Edge
May sit closer to the lens.
Image Center
Useful as the primary design reference.
Far Edge
May sit farther from the lens.
Example Throw-Ratio Calculation
Suppose one projector channel needs an effective image width of 4 meters after overlap is included.
The available lens-to-channel distance is approximately 3 meters.
The next step is to look for a projector or lens whose specified throw-ratio range includes approximately 0.75:1.
This is a preliminary optical check only. Final design should also verify focus, geometry, lens shift, mounting angle and image coverage across the complete curved surface.
Fixed Throw vs Zoom Lens
Fixed Throw
Provides a defined optical ratio and requires more precise projector positioning.
Zoom Lens
Provides a throw-ratio range and greater installation flexibility.
Short Throw Is Often Useful for Simulator Rooms
Compact Room
Large image from limited distance.
Operator Area
Helps keep light paths away from the user.
Panoramic Screen
Can simplify multi-projector positioning.
Throw Ratio Does Not Replace Geometry Correction
The correct lens creates the required image size, but the image may still need to be reshaped to follow the curved screen.
Throw Ratio
Controls image size.
Lens Shift
Controls optical position.
Warping
Controls image geometry.
Blending
Controls overlap transition.
Check Focus Across the Curved Surface
Because different parts of a curved screen can sit at different lens distances, focus should be checked across the entire projector image.
Center Focus
Check main optical axis.
Edge Focus
Check both sides of the image.
Uniform Detail
Important for simulator terrain and instruments.
Lens Shift Can Improve Projector Placement
Lens shift does not change throw ratio, but it can provide more flexibility when the projector cannot be mounted directly on the ideal optical axis.
Using optical lens shift before large digital corrections is generally preferable in professional installations.
Curved-Screen Calculation Checklist
| Parameter | Why It Matters |
|---|---|
| Screen Radius | Defines curvature |
| Screen Arc Length | Defines total physical surface coverage |
| Screen Height | Determines image aspect and vertical coverage |
| Field of View | Defines simulator visual coverage |
| Projector Quantity | Determines number of image channels |
| Channel Width | Defines individual projector coverage |
| Overlap | Needed for edge blending |
| Projection Distance | Used to calculate throw ratio |
| Throw Ratio | Determines suitable projector lens |
Recommended Calculation Workflow
Measure Screen Radius and Size
Document the real curved-screen geometry.
Define Field of View
Determine how much panoramic coverage is required.
Choose Projector Quantity
Divide the panorama into practical image channels.
Add Overlap
Include a blending area in each projector image.
Determine Projection Distance
Measure the realistic lens position for each channel.
Calculate Throw Ratio
Distance divided by effective image width.
Verify the Lens Range
Confirm the selected projector covers the calculated ratio.
Verify Geometry and Focus
Confirm performance across the complete curved screen.
Common Throw-Ratio Calculation Mistakes
Using Total Arc Length as Image Width
Curved-screen geometry requires channel-by-channel optical planning.
Forgetting Overlap
Edge-blending zones increase the image width required from each projector.
Using One Distance for the Entire Curved Surface
Lens-to-surface distance changes across the curved image.
Ignoring Focus
Correct throw ratio does not automatically guarantee uniform focus across a deep curve.
Ignoring Mounting Position
Structural constraints can change the actual projector-to-screen distance.
Choosing the Projector Too Early
Calculate screen coverage and optics before finalizing the projector model.
Curved Screen Throw Ratio FAQ
How do I calculate projector throw ratio?
Divide the projector-to-image distance by the width of the image that one projector must create.
Should I use curved-screen arc length as image width?
Not directly. Arc length describes the physical curved surface, while throw-ratio selection should be based on the effective optical coverage required from each projector channel.
Does overlap affect throw ratio?
Yes. The projector image must include the overlap region, so overlap increases the effective image width required from each channel.
Is 0.75:1 considered short throw?
It is generally within the short-throw range of many professional projector systems, but product classification varies between manufacturers. Always check the actual lens specification.
Can one projector cover a curved simulator screen?
Yes for some smaller screens, but wider fields of view often require multiple projectors.
Is a projector calculator enough for a curved screen?
Manufacturer calculators are very useful for lens and image-size verification, but complex curved installations should also verify real screen geometry, projector angles, focus and warping requirements.
Need Help Calculating Throw Ratio for Your Simulator?
Send us your curved-screen dimensions, screen radius, projector mounting positions and required field of view. Our team can help evaluate throw ratio, projector quantity, lens configuration, overlap and geometry requirements.
Screen Width / Arc Length • Screen Height • Screen Radius • Projection Distance • Projector Quantity • Field of View
