// Field of view calculator
			// Script written by Dave Fisher - 5/1/99
			// Evaluates lens format selection
			function lens_format(){
				if (document.lenscalc.radio1[0].checked){
				quarter_format()
				}
				else if (document.lenscalc.radio1[1].checked){
				third_format()
				}
				else if (document.lenscalc.radio1[2].checked){
				half_format()
				}
				else if (document.lenscalc.radio1[3].checked){
				twothirds_format()
				}
				else if (document.lenscalc.radio1[4].checked){
				oneinch_format()
				}
				else {
				}
			//Performs calculations for quarter inch formats
			function quarter_format(){
				var distance = document.lenscalc.distance.value
				var horizontal = document.lenscalc.horizontal.value
				var lens_size = document.lenscalc.lens_size.value
				var vertical = document.lenscalc.vertical.value

				if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
  				lens_size = distance/horizontal*3.2
				vertical = horizontal*.75
   				document.lenscalc.lens_size.value = RoundOff(lens_size)
				document.lenscalc.vertical.value = RoundOff(vertical)
   				}

				else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
				horizontal = distance/lens_size*3.2
				vertical = horizontal*.75
				document.lenscalc.horizontal.value = RoundOff(horizontal)
				document.lenscalc.vertical.value = RoundOff(vertical)
				}

				else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
				distance = horizontal/3.2*lens_size
				vertical = horizontal*.75
				document.lenscalc.distance.value = RoundOff(distance)
				document.lenscalc.vertical.value = RoundOff(vertical)
				}

				else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
				distance = vertical/2.4*lens_size
				horizontal = vertical/3*4
				document.lenscalc.distance.value = RoundOff(distance)
				document.lenscalc.horizontal.value = RoundOff(horizontal)
				}

				else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
				horizontal = vertical/3*4
				lens_size = distance/horizontal*3.2
				document.lenscalc.horizontal.value = RoundOff(horizontal)
				document.lenscalc.lens_size.value = RoundOff(lens_size)
				}

				else {alert("One or more of your answers was invalid. Please try again.")}
				}
			//Performs calculations for third inch formats
			function third_format(){
				var distance = document.lenscalc.distance.value
				var horizontal = document.lenscalc.horizontal.value
				var lens_size = document.lenscalc.lens_size.value
				var vertical = document.lenscalc.vertical.value

				if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
  				lens_size = distance/horizontal*4.4
				vertical = horizontal*.75
   				document.lenscalc.lens_size.value = RoundOff(lens_size)
				document.lenscalc.vertical.value = RoundOff(vertical)
   				}

				else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
				horizontal = distance/lens_size*4.4
				vertical = horizontal*.75
				document.lenscalc.horizontal.value = RoundOff(horizontal)
				document.lenscalc.vertical.value = RoundOff(vertical)
				}

				else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
				distance = horizontal/4.4*lens_size

			vertical = horizontal*.75
				document.lenscalc.distance.value = RoundOff(distance)
				document.lenscalc.vertical.value = RoundOff(vertical)
				}

				else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
				distance = vertical/3.3*lens_size
				horizontal = vertical/3*4
				document.lenscalc.distance.value = RoundOff(distance)
				document.lenscalc.horizontal.value = RoundOff(horizontal)
				}

				else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
				horizontal = vertical/3*4
				lens_size = distance/horizontal*4.4
				document.lenscalc.horizontal.value = RoundOff(horizontal)

			document.lenscalc.lens_size.value = RoundOff(lens_size)
				}

				else {alert("One or more of your answers was invalid. Please try again.")}
				}
			//Performs calculations for half inch formats
			function half_format(){
				var distance = document.lenscalc.distance.value
				var horizontal = document.lenscalc.horizontal.value
				var lens_size = document.lenscalc.lens_size.value
				var vertical = document.lenscalc.vertical.value

				if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
  				lens_size = distance/horizontal*6.4
				vertical = horizontal*.75
   				document.lenscalc.lens_size.value = RoundOff(lens_size)
				document.lenscalc.vertical.value = RoundOff(vertical)
   				}

				else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
				horizontal = distance/lens_size*6.4
				vertical = horizontal*.75
				document.lenscalc.horizontal.value = RoundOff(horizontal)
				document.lenscalc.vertical.value = RoundOff(vertical)
				}


				else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){

				distance = horizontal/6.4*lens_size

				vertical = horizontal*.75

				document.lenscalc.distance.value = RoundOff(distance)

				document.lenscalc.vertical.value = RoundOff(vertical)

				}



				else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){

				distance = vertical/4.8*lens_size

				horizontal = vertical/3*4

				document.lenscalc.distance.value = RoundOff(distance)

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				}



				else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){

				horizontal = vertical/3*4

				lens_size = distance/horizontal*6.4

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				document.lenscalc.lens_size.value = RoundOff(lens_size)

				}



				else {alert("One or more of your answers was invalid. Please try again.")}

				}

			//Performs calculations for two thirds inch formats

			function twothirds_format(){

				var distance = document.lenscalc.distance.value

				var horizontal = document.lenscalc.horizontal.value

				var lens_size = document.lenscalc.lens_size.value

				var vertical = document.lenscalc.vertical.value



				if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){

  				lens_size = distance/horizontal*8.8

				vertical = horizontal*.75

   				document.lenscalc.lens_size.value = RoundOff(lens_size)

				document.lenscalc.vertical.value = RoundOff(vertical)

   				}



				else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){

				horizontal = distance/lens_size*8.8

				vertical = horizontal*.75

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				document.lenscalc.vertical.value = RoundOff(vertical)

				}



				else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){

				distance = horizontal/8.8*lens_size

				vertical = horizontal*.75

				document.lenscalc.distance.value = RoundOff(distance)

				document.lenscalc.vertical.value = RoundOff(vertical)

				}



				else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){

				distance = vertical/6.6*lens_size

				horizontal = vertical/3*4

				document.lenscalc.distance.value = RoundOff(distance)

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				}



				else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){

				horizontal = vertical/3*4

				lens_size = distance/horizontal*8.8

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				document.lenscalc.lens_size.value = RoundOff(lens_size)

				}



				else {alert("One or more of your answers was invalid. Please try again.")}

				}

			//Performs calculations for one inch formats

			function oneinch_format(){

				var distance = document.lenscalc.distance.value

				var horizontal = document.lenscalc.horizontal.value

				var lens_size = document.lenscalc.lens_size.value

				var vertical = document.lenscalc.vertical.value



				if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){

  				lens_size = distance/horizontal*12.8

				vertical = horizontal*.75

   				document.lenscalc.lens_size.value = RoundOff(lens_size)

				document.lenscalc.vertical.value = RoundOff(vertical)

   				}



				else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){

				horizontal = distance/lens_size*12.8

				vertical = horizontal*.75

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				document.lenscalc.vertical.value = RoundOff(vertical)

				}



				else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){

				distance = horizontal/12.8*lens_size

				vertical = horizontal*.75

				document.lenscalc.distance.value = RoundOff(distance)

				document.lenscalc.vertical.value = RoundOff(vertical)

				}



				else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){

				distance = vertical/9.6*lens_size

				horizontal = vertical/3*4

				document.lenscalc.distance.value = RoundOff(distance)

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				}



				else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){

				horizontal = vertical/3*4

				lens_size = distance/horizontal*12.8

				document.lenscalc.horizontal.value = RoundOff(horizontal)

				document.lenscalc.lens_size.value = RoundOff(lens_size)

				}



				else {alert("One or more of your answers was invalid. Please try again.")}

				}

				}

			function RoundOff(s)

				{

				return Math.round(s*10)/10

				}