Lighting Intensity and Exposure Calculator
ANA›Life Services Authority›National Calculator Authority›Lighting Intensity and Exposure Calculator
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Lighting Intensity and Exposure Calculator
Calculate illuminance (lux), exposure value (EV), luminous intensity, and camera exposure settings using standard photometric and photographic formulas.
### Illuminance & Exposure Calculator
Calculation Mode
Illuminance from Point Source (Lux) Exposure Value (EV) from Lux Camera Settings from EV Distance from Desired Lux
Luminous Intensity (candela, cd)
Distance from Source (meters)
Angle of Incidence (degrees, 0 = perpendicular)
Illuminance (lux)
ISO Sensitivity
Exposure Value (EV)
ISO Sensitivity
Aperture (f-number)
Luminous Intensity (candela, cd)
Desired Illuminance (lux)
Calculate Results will appear here.
#### Formulas Used
Illuminance (Inverse Square Law): E = (I / d²) × cos(θ) where E = illuminance (lux), I = luminous intensity (cd), d = distance (m), θ = angle of incidence
Exposure Value from Lux (ISO 2720): EV = log₂(E × S / K) where E = illuminance (lux), S = ISO speed, K = incident light meter calibration constant (≈ 12.5)
EV from Camera Settings: EV = log₂(N² / t) − log₂(S / 100) where N = f-number (aperture), t = shutter speed (seconds), S = ISO
Shutter Speed from EV, Aperture, ISO: t = (N² × 100) / (2^EV × S) where t = shutter speed (s), N = aperture f-number, S = ISO
Distance from Desired Lux: d = √(I / E) where d = distance (m), I = intensity (cd), E = desired illuminance (lux)
#### Assumptions & References
function ligUpdateMode() { var mode = document.getElementById('lig-calc-mode').value; document.getElementById('lig-illuminance-inputs').style.display = (mode === 'illuminance') ? '' : 'none'; document.getElementById('lig-ev-inputs').style.display = (mode === 'ev') ? '' : 'none'; document.getElementById('lig-camera-inputs').style.display = (mode === 'camera') ? '' : 'none'; document.getElementById('lig-inverse-inputs').style.display = (mode === 'inverse') ? '' : 'none'; document.getElementById('lig-result').innerHTML = 'Results will appear here.'; }
function ligCalc() { var mode = document.getElementById('lig-calc-mode').value; var resultDiv = document.getElementById('lig-result');
try { if (mode === 'illuminance') { var I = parseFloat(document.getElementById('lig-intensity').value); var d = parseFloat(document.getElementById('lig-distance').value); var theta = parseFloat(document.getElementById('lig-angle').value) || 0;
if (isNaN(I) || I Please enter a valid luminous intensity (> 0 cd).'; return; } if (isNaN(d) || d Please enter a valid distance (> 0 m).'; return; } if (theta = 90) { resultDiv.innerHTML = 'Angle must be between 0° and 89.9°.'; return; }
var thetaRad = theta * Math.PI / 180; var E = (I / (d * d)) * Math.cos(thetaRad); var EV = Math.log2(E * 100 / 12.5);
var luxCategory = ''; if (E ' + 'Exposure Value (EV at ISO 100): ' + EV.toFixed(2) + '' + 'Inverse Square Factor (1/d²): ' + (1/(dd)).toFixed(6) + ' m⁻²' + 'cos(θ) Factor: ' + Math.cos(thetaRad).toFixed(4) + '' + 'Lighting Category: ' + luxCategory + '' + 'Formula: E = (I / d²) × cos(θ) = (' + I + ' / ' + (dd).toFixed(4) + ') × ' + Math.cos(thetaRad).toFixed(4) + ' = ' + E.toFixed(2) + ' lux';
} else if (mode === 'ev') { var E = parseFloat(document.getElementById('lig-lux-ev').value); var S = parseFloat(document.getElementById('lig-iso-ev').value) || 100; var K = 12.5;
if (isNaN(E) || E Please enter a valid illuminance (> 0 lux).'; return; } if (isNaN(S) || S Please enter a valid ISO value (> 0).'; return; }
var EV = Math.log2(E * S / K); var EVat100 = Math.log2(E * 100 / K);
// Suggest aperture/shutter combos at given ISO var combos = []; var apertures = [1.0, 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11.0, 16.0]; for (var i = 0; i = 1/8000 && t = 1 ? t.toFixed(1) + 's' : '1/' + Math.round(1/t) + 's'; combos.push('f/' + N + ' @ ' + tStr); } }
resultDiv.innerHTML = 'Exposure Value (EV at ISO ' + S + '): ' + EV.toFixed(2) + '' + 'EV at ISO 100: ' + EVat100.toFixed(2) + '' + 'Input Illuminance: ' + E.toFixed(2) + ' lux' + 'Calibration Constant (K): 12.5' + (combos.length > 0 ? 'Suggested Exposure Combos (ISO ' + S + '):' + combos.slice(0,5).join('') + '' : '') + 'Formula: EV = log₂(E × S / K) = log₂(' + E + ' × ' + S + ' / 12.5) = ' + EV.toFixed(2) + '';
} else if (mode === 'camera') { var EV = parseFloat(document.getElementById('lig-ev-input').value); var S = parseFloat(document.getElementById('lig-iso-cam').value) || 100; var N = parseFloat(document.getElementById('lig-aperture').value) || 2.8;
if (isNaN(EV)) { resultDiv.innerHTML = 'Please enter a valid EV value.'; return; } if (isNaN(S) || S Please enter a valid ISO value (> 0).'; return; } if (isNaN(N) || N Please enter a valid aperture f-number (> 0).'; return; }
// t = N² / (2^EV_adjusted), where EV_adjusted accounts for ISO // EV_scene = EV_100 = EV_measured + log2(S/100) // t = N² * 100 / (2^EV * S) var t = (N * N * 100) / (Math.pow(2, EV) * S); var tStr = t >= 1 ? t.toFixed(2) + ' seconds' : '1/' + Math.round(1/t) + ' second'; var luxEquiv = 12.5 * Math.pow(2, EV) / S * 100 / S * S; // E = K * 2^EV / S var luxVal = 12.5 * Math.pow(2, EV) / S;
var warning = ''; if (t ⚠ Shutter speed exceeds typical camera maximum (1/8000s). Consider higher f-number or lower ISO.'; if (t > 30) warning = '⚠ Shutter speed exceeds 30s. Consider wider aperture or higher ISO.';
resultDiv.innerHTML = 'Shutter Speed: ' + tStr + '' + 'Aperture: f/' + N + '' + 'ISO: ' + S + '' + 'Exposure Value (EV): ' + EV.toFixed(2) + '' + 'Equivalent Scene Illuminance: ' + luxVal.toFixed(2) + ' lux' + warning + 'Formula: t = (N² × 100) / (2^EV × S) = (' + (NN).toFixed(2) + ' × 100) / (' + Math.pow(2,EV).toFixed(4) + ' × ' + S + ') = ' + t.toFixed(6) + 's*';
} else if (mode === 'inverse') { var I = parseFloat(document.getElementById('lig-intensity-inv').value); var E = parseFloat(document.getElementById('lig-desired-lux').value);
if (isNaN(I) || I Please enter a valid luminous intensity (> 0 cd).'; return; } if (isNaN(E) || E Please enter a valid desired illuminance (> 0 lux).'; return; }
var d = Math.sqrt(I / E); var dFt = d * 3.28084;
// Also show lux at common distances var distTable = ''; var dists = [0.5, 1, 2, 3, 5, 10]; distTable = 'Illuminance at Common Distances:'; for (var i = 0; i '; }
resultDiv.innerHTML = 'Required Distance: ' + d.toFixed(3) + ' meters (' + dFt.toFixed(2) + ' ft)' + 'Luminous Intensity: ' + I + ' cd' + 'Desired Illuminance: ' + E + ' lux' + distTable + 'Formula: d = √(I / E) = √(' + I + ' / ' + E + ') = ' + d.toFixed(3) + ' m'; } } catch(err) { resultDiv.innerHTML = 'Calculation error: ' + err.message + ''; } }
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