Throw ratio is Throw/16x9_Width or Throw * .5625/H
Based on a 100" diagonal 2.35:1 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) -
h = Height of Screen
D = Diagonal
(DIAGONAL)^2 = h^2 =(2.35*h)^2
h^2 = (DIAGONAL/6.5225)^2, where "6.554" = 1+ (2.35)^2.
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