# Thread: Determining FOV with 3 projectors

1. ## Determining FOV with 3 projectors

Hello again everyone! We’ve made some great progress with our 747-400 simpit. Got the glare shield built as well as the beginning of our front panel. Since we have very limited space in our simpit room, we are trying to ensure we maximize FOV. So i’m back again to try and get more good advice from you guys on how to do this.

I’m trying to determine how to calculate the field of view for a generic 3 projector configuration. How does one go about doing this? I thought I understood how this was done, but unfortunately, I was mistaken.

For example, if I have a projector that produces an image with width w at x feet, etc… How is this done? I was trying to create a triangle using the image width and distance from the projector lens to the image, then dividing that into two right triangles and trying to determine the angle by taking the arc-tangent, then doubling it. I think I’m missing something here…

Any guidance?

2. ## Re: Determining FOV with 3 projectors

2 * atan(width / (2 * throw)) = beam angle.

For field of view, instead of using the distance from the lens to the screen, measure the distance from your eyes to the screen and do the same calculation. That is the field of view for each projector.

3. ## Re: Determining FOV with 3 projectors

Originally Posted by wledzian
2 * atan(width / (2 * throw)) = beam angle.

For field of view, instead of using the distance from the lens to the screen, measure the distance from your eyes to the screen and do the same calculation. That is the field of view for each projector.
Thank you very much for the reply. One quick question I have before I give the calculation another try is the 2 * throw component. Is throw the throw ratio of the projector?

4. ## Re: Determining FOV with 3 projectors

'throw' is distance from the lens to the screen.
'throw ratio' is (image width) / throw.

5. ## Re: Determining FOV with 3 projectors

If my eyes are, for example, 66" from the screen, and my image width given the distance from projector to screen is 102", then ...

2 * atan(102 / (2 * 66)) ~= 75.38

Or ~= 226.16 degrees for three projectors in the same configuration.

6. ## Re: Determining FOV with 3 projectors

That's correct. For that FOV, set zoom = 0.42

7. ## Re: Determining FOV with 3 projectors

Originally Posted by wledzian
That's correct. For that FOV, set zoom = 0.42

Thanks again for all of your help.

How is the 0.42 zoom determined? I assume this is a FSX camera configuration option?

8. ## Re: Determining FOV with 3 projectors

It's a camera setting. I'm also building a display which uses multiple projectors, and got tired of the trial-and-error method of matching the zooms, so I reverse-engineered the zoom formula and made a tool to do it for me.
http://www.mycockpit.org/forums/show...r-tool-updated!

9. ## Re: Determining FOV with 3 projectors

Excellent.

I didn't realize you had created the WindowMaker tool. Thanks very much for all of the help.

10. ## Re: Determining FOV with 3 projectors

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