Christie Projector Throw Distance Calculator

The Christie projector throw distance calculator on this page works out how far a Christie projector must be placed from the screen to fill a chosen image width, or the reverse: given a set distance, it returns the image width and the zoom range. You enter the projector model’s lens specs (minimum and maximum throw ratio), the desired screen width or the available throw distance, and the calculator outputs the required distance range or the achievable image size range.

Formula

Throw distance is calculated by multiplying the throw ratio by the screen width. The formula is:

Throw Distance (D) = Throw Ratio (TR) × Screen Width (W)

Where:

• D = distance from the projector lens to the screen, in meters (or feet)
• TR = throw ratio, a dimensionless number (often written as e.g. 1.0–1.5:1)
• W = screen width, in the same unit as D

Because most zoom lenses have a range, you get a minimum and a maximum distance. The calculator uses the minimum throw ratio for the closest position and the maximum throw ratio for the farthest.

Worked Example

Using the default values: a lens with a throw ratio range of 0.8–1.2 and a screen width of 3 meters.

1. Minimum distance: 0.8 × 3 = 2.4 m
2. Maximum distance: 1.2 × 3 = 3.6 m

So the projector must be placed between 2.4 and 3.6 meters from the screen to fill a 3-meter-wide image. If you cannot place it within that range, you need a different lens or a different screen size.

Understanding Throw Ratio and Why It Matters

The throw ratio is the fundamental spec for any projector lens. It is the ratio of the distance from the lens to the screen divided by the width of the projected image. For example, a throw ratio of 1.0 means that for every 1 meter of image width, the projector must be 1 meter away. A ratio of 0.5 means the projector can be placed closer—0.5 meters away for 1 meter of width—which is typical of short-throw lenses. Christie publishes throw ratio ranges for every lens it sells, usually printed on the lens barrel and in the datasheet.

Knowing the throw ratio lets you plan a room before you buy. If you have a fixed screen and a fixed projector position, the throw ratio determines whether the image will fit. If it does not fit, you either move the projector, change the screen, or select a different lens.

How to Use the Calculator for Your Christie Model

To get a useful result, you need the throw ratio range for your specific Christie projector and lens. Here is the step-by-step process:

1. Find your projector model’s lens specs. Look in the user manual, the datasheet, or on the lens itself. The throw ratio is usually listed as a range, e.g., 0.8–1.2:1.
2. Measure your screen width (not the diagonal). If you only know the diagonal and aspect ratio, compute width: for 16:9, width = diagonal × 0.871; for 4:3, width = diagonal × 0.8.
3. Enter the minimum and maximum throw ratios into the calculator.
4. Enter the screen width.
5. Read the minimum and maximum throw distances. The projector must be placed somewhere between those two distances to fill the screen exactly.

If you need to work backwards—you have a fixed mount position and need to know what screen width you can fill—simply rearrange the formula: W = D / TR. For a given distance, divide by the throw ratio range to get the range of screen widths you can fill.

Common Mistakes and Misconceptions

A frequent error is using the diagonal screen size instead of the width. Throw ratio is always based on width, not diagonal. Mixing units is another common problem: if you measure the distance in feet and the screen width in meters, the result will be wrong. Always use the same unit for both.

Another misconception is that the throw distance is measured from the front of the projector. It is actually measured from the front of the lens (the lens surface), not the case or the back. If you are measuring from the wall behind the projector, subtract the depth of the projector and the lens offset.

Also, the throw ratio range assumes the lens is at its widest zoom (minimum ratio) and most telephoto (maximum ratio). If you set the zoom in between, the actual distance will be between the two calculated values. The calculator gives the full range, so you have flexibility.

Choosing the Right Lens for Your Room

Christie projectors often have interchangeable lenses. The lens you choose determines the throw ratio range. For a typical conference room with a 3-meter-wide screen and a projector mounted 4 meters away, you would need a lens with a throw ratio around 1.3 (4 / 3). A standard zoom lens with a range of 1.2–1.8 would work, while a short-throw lens (0.8–1.2) would not reach that distance.

For home theaters, a throw ratio of 1.0–1.5 is common. For classrooms where the projector is mounted close to the screen, a short-throw or ultra-short-throw lens (below 0.8) is often used to avoid shadows and glare. For large venues like auditoriums, long-throw lenses (2.0 and above) are needed because the projector is far from the screen.

Limitations of the Calculator

This calculator assumes a flat screen and a lens that is perpendicular to the screen. In reality, keystone correction or lens shift can alter the effective image size and distance. Also, the throw ratio is a nominal value; actual lenses may vary slightly due to manufacturing tolerances. For critical installations, always verify with a physical test or use Christie’s official projection design tools, which also account for lens offset, aspect ratio, and screen gain.

The calculator also does not factor in the projector’s vertical and horizontal lens shift capabilities. Those do not change the throw distance, but they do affect where the image lands on the screen. If you are ceiling-mounting the projector, you need to know the lens shift range to align the image correctly.

Frequently Asked Questions

What is the throw distance for a Christie projector?

There is no single answer because it depends on the model and lens. A typical Christie projector with a standard zoom lens (throw ratio 1.2–1.8) and a 2-meter-wide screen would need to be placed 2.4 to 3.6 meters away. Check your lens’s throw ratio and multiply by your screen width.

How do I find the throw ratio for my Christie projector?

The throw ratio is printed on the lens barrel (e.g., “1.2–1.8:1â€�) and listed in the projector’s spec sheet or user manual. If you cannot find it, search the model number plus “lensâ€� on the Christie support site.

Can I use the calculator for a projector with a fixed lens (no zoom)?

Yes. If the lens has a fixed throw ratio, enter the same value for both minimum and maximum. The calculator will then give a single distance (or a very narrow range) instead of a range.

What if my screen is measured diagonally?

Convert the diagonal to width first. For a 16:9 screen, multiply the diagonal by 0.871; for 4:3, multiply by 0.8. Then enter the width. Using the diagonal directly will give an incorrect throw distance.

Does the calculator work in feet and inches?

Yes, as long as you use the same unit for both screen width and throw distance. The calculator is unit-agnostic because the throw ratio is dimensionless. If you enter width in feet, the result will be in feet.

Why is the calculated distance different from what I see when I set up the projector?

Possible reasons: you measured from the wrong point (should be from the lens), the zoom is not at the extremes, or the screen is not exactly the width you think. Also, some projectors have a slight offset between the lens center and the image edge. Re-check your measurements and the lens zoom position.

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in tr_min | Min throw ratio | - | 0.8 | 0
in tr_max | Max throw ratio | - | 1.2 | 0
in sw | Screen width | m | 3 | 0
out dist_min | Min throw distance | m | tr_min * sw | 2
out dist_max | Max throw distance | m | tr_max * sw | 2