# Math Equation Help

2 replies to this topic

### #1 Jamie Metzger

Jamie Metzger
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Posted 22 November 2006 - 03:37 AM

So I have to shoot a birds eye of an alleyway about 23meters long. The roof is about 20 meters tall.

What lens would I need to be able to see the whole alleyway, also if I need a jib to get me higher, what height and lens?

I did some research and some rough number crunching to come up with a 30mm lens.

Anyone know how to check this out, if it's correct?
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### #2 Mark Dunn

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Posted 22 November 2006 - 05:12 AM

Using similar triangles, I make it a 20mm.
You're 20m above the alley, you need a 25m horizontal FOV.
35mm. film is about 25mm. wide, so by similar triangles you need a 20mm.
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### #3 Jamie Metzger

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Posted 22 November 2006 - 02:29 PM

Using similar triangles, I make it a 20mm.
You're 20m above the alley, you need a 25m horizontal FOV.
35mm. film is about 25mm. wide, so by similar triangles you need a 20mm.

Remember though, I need to be on a jib arm above the roof to get that height. I don't need to see the rooftop of the alley, but I need to see the whole length of the alley.

So a 25mm on a jib arm would be ideal
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