Road Train !!!!!!!!!!

by Russell McMahon

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I have a setup of two static cameras that film a sport court. One camera for the left side, and the other for the right side.

In order to recompose the image of the full court, the cameras must be as close as possible (in order to have their focal point as close as possible). Therefor, the setup has the form of a "V".

I have two possibilities:

  • I can close the lenses : the camera on the right films the left side and the camera on the left films the right side (the setup has the form of a "V" upside down)
  • Or I can close the back of the cameras : the camera on the right films the right side and the camera on left films the left side (it is a "V").

My question:

How can I compute which solution is the best, depending on the angle between the two cameras, the focal length of the lenses, and the size of the cameras?

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1  
Is this a video or photography question? –  jrista Mar 22 '13 at 17:49
    
this is a video setup –  Jav Mar 25 '13 at 8:22
    
Is there anything that would be particularly different because it happens to be video? –  mattdm Mar 25 '13 at 11:26

4 Answers 4

How can I compute which solution is the best, depending on the angle between the two cameras, the focal length of the lenses, and the size of the cameras?

It seems unlikely to matter which of the two setups you choose. Consider this:

  • pick one of the configurations you describe above

  • swap the positions of the two cameras, keeping the orientation of each camera the same

At this point, you will have recreated the other configuration. The only difference between the two is that the position of each camera in space changes by 6 or 8 inches. You can achieve exactly the same exchange of relative positions by moving each camera forward or backward along their respective optical axes.

The angle between the cameras and the relationship of each camera to the plane of court and the court's center line will be much more important than which camera ends up on the right and which on the left.

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As long as they are near each other, I don't believe it will matter. The area that each camera sees is going to be the same once you get past the first foot or so. If you think about it, the angle each camera is looking is the same in either case, only the side of each other that they are on changes. (If I'm understanding your setup correctly.)

The real thing you would want to play with is how much overlap you need between the shots to minimize any distortion caused near the edges of the lens and the best bet for this is probably going to be experimentation. Also, depending on how far away from the court the cameras are you may want to try setting them up with an offset between them and both facing forward at different parts of the court. They need to be far enough away not to generate an unacceptable level of distortion on the closer portion of the field of view that would have a different amount of overlap.

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Ideally the two cameras should cross at the nodal point of the lenses and form an X. Unfortunately, two objects can't occupy the same space at the same time. Whichever setup allows the nodal points of the lenses of each camera to be closest to each other will yield the best results. This will vary based on what camera and lenses you are using, but off hand I would think that for typical cameras and lenses it would be for the right camera to film the left and vice versa.

In general, whenever you are stitching two images together the longer the focal length, the less distortion you will have to deal with when you overlap them. In practical terms this means pull back as far as you can and use the longest focal length that allows coverage of the area you need to film so that the angle between the two cameras is minimized.

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Thank you but this does not answer the question ... I know that I have to pull back as far as I can but in my case it is not possible . Whence my question ... –  Jav Mar 25 '13 at 8:12

To put those two lenses as close to eachother as possible... Have you considered pointing cameras to eachother (at a slight angle) and put a V-shaped mirror on the middle? This will definitely get your focal points as close as possible.

--      /\      --
  |>   /  \   <|
--    /    \    --

Like so... Hopefully you understand the idea behind this. The only problem with this setup I see is quality of your mirrors and of course keeping them clean just as well as your lenses.

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