// Javascript copyright Sean T. McHugh
// http://www.cambridgeincolour.com

var airy1 = new Image(); airy1.src = "graphics/airy-f32.jpg"; airy1.src = "graphics/airy-f22.jpg"; airy1.src = "graphics/airy-f16.jpg"; airy1.src = "graphics/airy-f11.jpg"; airy1.src = "graphics/airy-f5p6.jpg"; airy1.src = "graphics/airy-f4.jpg"; airy1.src = "graphics/airy-f2p8.jpg"; airy1.src = "graphics/airy-f2.jpg";
var grid1 = new Image(); grid1.src = "graphics/airy-grid-10D.png"; grid1.src = "graphics/airy-grid-1D.png"; grid1.src = "graphics/airy-grid-1Ds.png"; grid1.src = "graphics/airy-grid-1DsMkII.png"; grid1.src = "graphics/airy-grid-1DMkII.png"; grid1.src = "graphics/airy-grid-D70.png"; grid1.src = "graphics/airy-grid-D2X.png"; grid1.src = "graphics/airy-grid-G6.png";

// coc(35mm)/coc(x) = Diag(35mm) / Diag(x) = FLM
// Diag(x) = Width(x) * sqrt(1+1/AR^2), AR == aspect ratio
// horizonalresolution = sqrt(AR*megapixels)

<!-- Begin Calculator
function doField(form) {
coc1 = (document.form.format.options[document.form.format.selectedIndex].value);
aperture = (document.form.aperture.options[document.form.aperture.selectedIndex].value);
unit = form.unit.value;
view_dist = (form.view_dist.value)/100;
print_size = form.print_size.value;
eyesight = (document.form.eyesight.options[document.form.eyesight.selectedIndex].value);
megapixels = form.megapixels.value;

if (isNaN(print_size)) {
	alert('Please enter a numerical value for the maximum print dimension.');
	document.form.print_size.focus();
	document.form.print_size.select();
	}
if (isNaN(megapixels))  {
	if (megapixels != "?") {
	alert('Please enter a numerical value for the megapixel resolution.');
	document.form.megapixels.focus();
	document.form.megapixels.select();
		}
	}

if (megapixels == "?") {
	form.pix_out.value = "?";
	}
else {
	if (coc1 < 0.0165) {
		aspectratio = 4/3;
		}
	else {
		aspectratio = 3/2;
		}
	pixelsize = (coc1 / 0.032) * 43266.6 / ( Math.sqrt(aspectratio * megapixels * 1e6) * Math.sqrt(1 + 1 / (aspectratio * aspectratio)) ); // 43266.6 is diagonal for 35mm format; 0.032 is coc for 35mm	
	form.pix_out.value = Math.round(10 * pixelsize) / 10;
	}

if (document.form.usepixels.checked  == true) {
	if (megapixels == "?") {
		alert('Please enter a numerical value for the megapixel resolution.');
		document.form.megapixels.focus();
		document.form.megapixels.select();
		}
	else {
		form.coc_out.value = Math.round(10 * 2 * pixelsize) / 10;
		CoC = form.coc_out.value;
		}
	}
else {
	CoC = 1000 * coc1 * eyesight * (view_dist / 0.25) * (10 * unit / print_size); //in microns
	form.coc_out.value = Math.round(100 * CoC) / 100;
	}

airy = 2.43932 * 550e-9 * aperture * 1e6;
form.airy_out.value = Math.round(10 * airy) / 10;
if (CoC < airy) {
	form.diff_out.value = "YES";
	}
else {
	form.diff_out.value = "NO";
	}
}
//  End Calculator -->