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: Osram Par 38 120W: TH

  • Display Results
  • Graphs

Illuminant: Par 38 120W

CCT: 2594K | Duv: 0.0007 | CQS: 99.4

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
X113.3719113.6649
Y100100
Z27.776828.8204
u0.26730.2674
v0.35360.3529

 VS01VS02VS03VS04VS05VS06VS07VS08VS09VS10VS11VS12VS13VS14VS15
Δx0.0000.000-0.000-0.000-0.0000.0000.0010.0020.0020.0020.0030.0030.0020.0020.001
Δy0.0010.0010.0010.0010.0010.0010.0020.0030.0040.0050.0050.0040.0030.0020.001
ΔC*ab0.030.02-0.08-0.31-0.23-0.29-0.160.030.120.160.12-0.06-0.140.050.07
ΔE*ab0.10.10.10.30.20.30.30.20.20.20.20.20.10.10.1
ΔE*abSF0.10.10.10.30.20.30.30.20.10.00.20.20.10.10.1
CQ100100100999999999910010010099100100100
p(ΔC*ab)0.030.020.000.000.000.000.000.030.120.160.120.000.000.050.07
p(ΔC*abWL)0.030.020.000.000.000.000.000.030.120.160.120.000.000.050.07

IlluminantVS01VS02VS03VS04VS05VS06VS07VS08VS09VS10VS11VS12VS13VS14VS15
x0.64950.59580.56650.53380.48840.44370.36580.33880.33740.30540.29690.37330.50220.55510.5997
y0.32630.37950.41620.44280.47750.49940.52370.47190.42970.38380.34750.33370.34530.34720.3372
u0.46260.37460.33020.29470.25200.21900.17110.16970.18040.17460.18060.23860.32720.36670.4103
v0.34860.35790.36390.36670.36950.36970.36740.35460.34460.32920.31700.32000.33750.34400.3460
L*47.8066.3372.7678.5377.1464.9353.1652.0052.6542.4434.0835.4751.2562.3954.86
a*56.7740.6924.048.43-13.54-27.22-44.44-41.41-34.09-28.05-19.41-0.9925.0941.0449.48
b*39.1954.4271.6569.2258.4235.8610.44-15.27-29.55-43.18-47.01-41.49-19.38-0.5815.07
C*ab68.9867.9575.5869.7459.9645.0245.6544.1445.1151.4950.8641.5031.7141.0451.72

Black BodyVS01VS02VS03VS04VS05VS06VS07VS08VS09VS10VS11VS12VS13VS14VS15
x0.64930.59570.56660.53400.48840.44340.36490.33720.33540.30310.29440.37030.50000.55360.5987
y0.32570.37880.41550.44200.47650.49820.52170.46870.42580.37930.34260.32940.34260.34550.3360
u0.46290.37500.33080.29520.25240.21920.17110.16960.18040.17450.18050.23840.32730.36670.4104
v0.34840.35770.36380.36650.36930.36940.36690.35370.34350.32770.31520.31810.33640.34330.3455
L*47.8766.3672.7578.5177.1064.9053.1452.0052.6742.4834.1235.5051.2962.4454.91
a*56.6840.5723.968.35-13.59-27.32-44.54-41.46-34.06-27.94-19.23-0.8125.1940.9949.40
b*39.2754.4871.7669.5558.6436.1410.69-15.05-29.40-43.06-46.96-41.55-19.48-0.6115.09
C*ab68.9667.9375.6670.0560.1945.3045.8144.1145.0051.3350.7441.5631.8541.0051.66