// ------------------------------------------
// Studio Spot Beam size and output calculator
// Copyright High End Systems 1998
// Ver 1.0 MWW 8-26-98
// ------------------------------------------


function validate(a)
{
var c
	if(a.value.length == 0) {
		c = 0.0
	} else {
		c=a.value
		if (c.indexOf("m") != -1) c=c.substring(0,c.length-2)
		if (c.indexOf("ft") != -1) c=c.substring(0,c.length-3)
	}
return c
}


function lightingcalculator(form)
{	
  var Units 			// Metric or English Units
  var Throw			// Throw Distance
  var Image 			// Image Diameter
  var Out 			// Output
  var LightUnits 		// Temp variable for light units
  var RequiredImage  		// Required Image Size at Mid Zoom
  var LensSystem  		// Normal,Narrow or WideAngle Lens
  var LensFactor		// Temp variable for Beam angle factor
  var LensOutput		// Output at throw of 1 unit (i.e Candelas)

	Throw=validate(form.Throw) 
	RequiredImage=validate(form.RequiredImage)

	Units = form.Units.options[form.Units.selectedIndex].value
	LensSystem = form.LensSystem.options[form.LensSystem.selectedIndex].value

	if (Units == "m") {
		LightUnits = "lux"
	} else { 
		LightUnits = "fc"
	}

	if (LensSystem == "Normal") {
		LensFactor = 0.317
		LensOutput = 243000
	} 

	if (LensSystem == "Narrow") {
		LensFactor = 0.228
		LensOutput = 342000
	}
	
	if (LensSystem == "Wide") {
		LensFactor = 0.536
		LensOutput = 77400
	}

	if (Throw != 0 && RequiredImage != 0 ) {
		RequiredImage = 0
	}

	if (Throw ==0 && RequiredImage ==0) {
		Throw = 1 
	}


	if (Throw == 0) {
		Throw = RequiredImage / LensFactor
		Image = RequiredImage
	}

	if (RequiredImage == 0) {
		Image = Throw * LensFactor
	}

	RequiredImage = Image


	if (Throw != 0){
		Out = LensOutput / Throw / Throw 
		
	}

	Throw = Math.round(10 * Throw) / 10
	Image = Math.round(10 * Image) / 10
	RequiredImage = Math.round(10 * RequiredImage) / 10
	Out = Math.round(Out)

	form.Throw.value = "" + Throw + " " + Units
	form.RequiredImage.value = "" + RequiredImage + " " + Units 
	
	form.Out.value = "" + Out + " " + LightUnits

}

function clearcalculator(form)
{	
	form.Throw.value = ""
	
	form.Out.value = ""
	form.RequiredImage.value = ""
}