# Planning for light throw

Discussion in 'Lighting and Electrics' started by FTOTY, Feb 17, 2005.

1. ### FTOTYMember

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So, this is my second time designing lights for a main stage production and I need help with one thing: light throw. How do you design/plan for light throw? I might be using the term, and if so, I mean where the light lands-how wide, any shadows, and the like. So far this is the only problem I'm having with my. I was also wondering if there were any lighting design software available online. I've been working from scratch, which isn't bad, but some help would be nice every now and then.

2. ### cutlunchActive Member

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Location:
Auckland, New Zealand
Go to the manufacturer's website for the lights you have. And download the light characteristics for each light you are using. This is a chart showing beam size, light level and throw distance. This will give you the info you need.

3. ### LesWell-Known Member

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DFW, Tx.
What you are looking for in your instruments is 'photometrics'. This information specifies almost every characteristic of the light's beam. As far as shadows go, you will have them. It's a natural part of lighting design. Embrace it. The challenge is getting them where you want them.

4. ### Inaki2Active Member

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Chicago, Illinois
5. ### squigishMember

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This is one of the places where a sectional proves it's value, you need both the plan (horizontal) and sectional (vertical) distances to calculate your throw distance using the pythatorean theorem (a^2+b^2=c^2).

6. ### Inaki2Active Member

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568
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Location:
Chicago, Illinois
If you want the math to do it yourself:

Terminology:
BD: Beam Diameter @ Throw Distance
TD: Throw Distance (how far away the light is to the object)
mf: Multiplying Factor (this is a trigonometric offspring to the field angle)
fc: Footcandles (a measure of light)
pc: Peak Candela (the manufacturer must supply tou with this)

mf: 2 x TAN(field angle/2)
BD: mf x TD
fc: pc/TD^2

7. ### zac850Well-Known Member

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Location:
New York
In light of trying to avoid school work by doing theater work (what, am I alone in that?), I would agree going to

http://www.paul-pelletier.com/LDCalculator/LDCalculatorPage.htm

I use that program (in virtual PC) and it has been a god send. It does any calculation you need, plus some.

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