Further information relating to examination of SPD Curves

This web-page is designed to display example spectral distribution curves for tested light sources. For more information relating to the graphing library used in this page see the dygraphs website. For more information about the project in general contact Joseph Padfield.


Calculating the CQS and Duv from the SPD curve of: Test Lamp: LED

  • Display Results
  • Graphs

Illuminant: Test Lamp

CCT: 5054K | Duv: 0.0002 | CQS: 91.4

CQS Calculations

CQS - Calculation Summary

  • Find the chromaticity xy co-ordinates of the test source from its calculated CIE 1931 color space XYZ values.
  • Determine the correlated color temperature (CCT) of the test source and select the appropriate black body reference source.
  • Illuminate the fifteen CQS test colour samples, alternately using both sources.
  • Calculate the CIE 1976 (L*, a*, b*) color space coordinates of the light reflected by each sample.
  • Calculate the various ΔC*ab and ΔE*ab values as indicated in the table below.
  • Calculate the overall CQS using the equation: CQS = 10 * log(exp(((100-ScalingFactor*OverAllΔE*abSF))/10)+1)
    • With the ScalingFactor of 3.2
    • OverAllΔE*abSF = √[(ΔE*abSF_1)² + (ΔE*abSF_2)² + ... + (ΔE*abSF_15)²]
  • See the information page for more information.

IlluminantBlack Body
X97.92496.3244
Y100100
Z87.040583.5467
u0.21070.2086
v0.32270.3249

 VS01VS02VS03VS04VS05VS06VS07VS08VS09VS10VS11VS12VS13VS14VS15
Δx-0.002-0.002-0.0020.0000.0000.0040.0050.0050.0030.0020.001-0.002-0.003-0.003-0.004
Δy-0.001-0.0010.0000.001-0.0000.000-0.002-0.008-0.012-0.016-0.018-0.013-0.006-0.005-0.005
ΔC*ab-1.38-1.11-0.111.812.102.400.21-2.31-2.41-0.591.922.82-0.34-0.46-0.93
ΔE*ab1.62.12.72.92.62.51.92.43.35.35.93.60.50.61.1
ΔE*abSF1.62.12.72.31.50.81.82.43.35.35.62.30.50.61.1
CQ959391939597949289838293989897
p(ΔC*ab)0.000.000.001.812.102.400.210.000.000.001.922.820.000.000.00
p(ΔC*abWL)0.000.000.001.812.102.400.210.000.000.001.922.820.000.000.00

IlluminantVS01VS02VS03VS04VS05VS06VS07VS08VS09VS10VS11VS12VS13VS14VS15
x0.57510.52800.50580.46260.41350.36220.28280.24450.23370.20640.19860.23600.33450.40840.4722
y0.32020.37860.43450.47280.49440.50560.48920.38730.32190.25610.21260.20410.25810.28450.2968
u0.40420.32550.28090.23880.20400.17370.13620.13660.14620.14590.15410.18960.24650.29180.3363
v0.33750.35020.36200.36610.36600.36360.35340.32460.30200.27150.24750.24610.28530.30500.3170
L*41.1860.7768.8376.6177.1866.6056.6655.9456.5446.4737.6237.0649.5658.3349.56
a*55.2441.3721.68-0.12-20.58-35.22-50.46-42.22-29.69-16.91-3.6013.0127.6943.5549.63
b*27.4545.4267.2073.5664.5647.0223.54-3.72-20.79-36.72-43.52-42.64-24.81-9.524.13
C*ab61.6961.4470.6173.5667.7658.7555.6842.3836.2540.4343.6744.5837.1844.5849.80

Black BodyVS01VS02VS03VS04VS05VS06VS07VS08VS09VS10VS11VS12VS13VS14VS15
x0.57720.52950.50750.46220.41310.35860.27760.23970.23060.20420.19760.23830.33740.41090.4761
y0.32160.37960.43410.47230.49460.50510.49090.39500.33360.27240.23030.21750.26360.29000.3019
u0.40470.32600.28210.23880.20380.17190.13320.13210.14100.13940.14720.18560.24590.29050.3359
v0.33820.35060.36200.36600.36600.36320.35340.32640.30600.27890.25740.25420.28820.30750.3194
L*41.1760.6568.5176.3576.8366.4956.7656.3056.9746.9938.0637.2749.6858.4349.61
a*56.8143.3924.272.12-18.57-34.39-51.02-44.48-32.95-21.77-8.8210.0528.1444.0650.51
b*27.3945.0566.4471.7262.9744.6421.77-4.30-20.21-34.76-40.81-40.54-24.81-9.334.72
C*ab63.0762.5570.7371.7565.6556.3555.4744.6938.6641.0141.7541.7737.5245.0350.73