----- Original Message ----- From: "Tom Miller" <tomwmil...@attbi.com> To: <pinhole-discussion@p at ???????>
> I've read a rule > of thumb that at 30 degrees the fall of is one stop and that at 45 degrees > it is two stops. It seems like there is a possibly handy formula in there. Tom, Forgot answering this other question. That rule of thumb is good, but to be precise, 1 stop is at 32.76 degrees. A formula to find the angle at which a specific fall off is found would be: If S = stops of fall off Angle = ArcCosine [(1 / 2^S)^0.25] or for better clarity: http://members.rogers.com/gpenate/angle.gif for 1 stops it would be: Angle = ArcCosine [(1 / 2^1)^0.25] Angle = ArcCosine [(1 / 2)^0.25] Angle = ArcCosine [0.5^0.25] Angle = ArcCosine [0.840896] Angle = 32.76 degrees for 2 stops it would be: Angle = ArcCosine [(1 / 2^2)^0.25] Angle = ArcCosine [(1 / 4)^0.25] Angle = ArcCosine [0.25^0.25] Angle = ArcCosine [0.70710678] Angle = 45 degrees Guillermo
