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# Throw Distance Calculation

What is the formula to calculate the throw distance for Anamorphic screens? If I have a 100" 2.35:1 to screen how do I calculate throw distance? I am looking at the JVC DLAX75R.

Next, how do I derive the 16:9 aspect ratio?
Edited by dravpilot - 12/25/12 at 7:38pm

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Two questions first:

1. Do you mean "How do I calculate Throw RATIO"?

2. Is your 2.35 screen 100" WIDE or DIAGONAL?
1.) Yes

2.) 100" Diagonal.
Throw ratio is Throw/16x9_Width or Throw * .5625/H

Based on a 100" diagonal 2.35:1 screen ...

2.35 Screen
39.2 = height
92.0 = width
100.0 = diagonal (we knew that already!)

16x9 Screen (based on height)
69.6 = 16x9 width

So divide whatever you throw is (in inches) by 69.6 for the Throw Ratio.

For the mathematically inclined...

When the measurement of a scope screen is the DIAGONAL
Height for a 2.35:1 screen will be DIAGONAL/2.554
Height for a 2.40:1 screen will be DIAGONAL/2.6

This is based on the following formula (for 2.35:1 screens) -

where

h = Height of Screen
D = Diagonal

(DIAGONAL)^2 = h^2 =(2.35*h)^2

= (6.5225*h)^2

Leaving...

h^2 = (DIAGONAL/6.5225)^2, where "6.554" = 1+ (2.35)^2.

and thus:

h = (DIAGONAL/2.554)

For 2.40 screens substitute "2.6" for "2.554" in the equation above.

Once you have a value for "h" then multiply by 16/9 to get the 16x9 Screen Width, then use this in the Throw Ratio Formula (Throw/16x9_WIDTH).

Clear as mud?

Of course you can further simply these to:

2.35 screen: TR = THROW/(DIAGONAL*0.69609807)
2.40 screen: TR = THROW/(DIAGONAL*0.683760684)

But if I just put it that way you might not get how the formula was derived.
Edited by Aussie Bob II - 12/26/12 at 6:31pm
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