speceval

The speceval function evaluates spectral power distribution(s) for several parameters.

Note: The function also evaluates the α-opic daylight equivalents, e.g. the Melanopic Equivalent Daylight Illuminance (MEDI). Since the spectral power distribution can also represent other photometric units, as e.g. the luminance, the return values are named with Y instead of I for illuminance – as Y represents the photometric unit in question – hence MEDI is given as MEDY.

Usage:

data = speceval(lam,spec)

Where:

Parameter	Description
data	Is a return struct containing all relevant information: – X: containing the non-normalized X Tristimulus values – Y: containing the non-normalized Y Tristimulus values, representing the photometric unit in question – Z: containing the non-normalized Z Tristimulus values – SC: retinal ganglion cells: s-cone-opic s_{\text{sc}} or cyanopic – MC: retinal ganglion cells: m-cone-opic s_{\text{mc}} or chloropic – LC: retinal ganglion cells: l-cone-opic s_{\text{lc}} or erythropic – RH: retinal ganglion cells: rhodopic s_{\text{rh}}, or scotopic NOTE: K_{\text{m}}=1~\frac{\text{lm}}{\text{W}} according to CIE S 026 – MEL: retinal ganglion cells: melanopic s_{\text{mel}} – sc_EDY: s-cone-opic equivalent daylight Y – mc_EDY: m-cone-opic equivalent daylight Y – lc_EDY: l-cone-opic equivalent daylight Y – rh_EDY: rhodopic equivalent daylight Y – MEDY: melanopic equivalent daylight Y – Tcp: correlated colour temperature (CCT) in K – x: normalized Tristimulus value x for 2 degree standard observer – y: normalized Tristimulus value y for 2 degree standard observer – z: normalized Tristimulus value z for 2 degree standard observer – x10: normalized Tristimulus value x for 10 degree standard observer – y10: normalized Tristimulus value y for 10 degree standard observer – z10: normalized Tristimulus value z for 10 degree standard observer – u: chromaticity coordinate u in CIE 1960 – v: chromaticity coordinate v in CIE 1960 – v_: chromaticity coordinate v’ in CIE 1976 – L: CIE L^* chromaticity coordinate in L^*a^*b^* – a: CIE a^* chromaticity coordinate in L^*a^*b^* – b: CIE b^* chromaticity coordinate in L^*a^*b^* – C: CIE C^* chromaticity coordinate in L^*C^*h^° – h: CIE h\degree chromaticity coordinate in L^*C^*h\degree – Ra: general Colour Rendering Index – Rf: general Colour Fidelity Index – duv: contains the delta uv distance to a planck illuminant of the same CCT
lam	Defines the wavelengths of the given spectrum/spectra.
spec	Provides the input spectrum/spectra, row-wise.

Examples

Evaluate the spectral power distribution of standard illuminant ‘FL4’:

lam = 380:780;
spec = ciespec(lam,'FL4');
speceval(lam,spec)

See also: ciespec

Result:

ans =

  scalar structure containing the fields:

    X = 1.0911e+06
    Y = 9.9966e+05
    Z = 3.8800e+05
    SC = 296.82
    MC = 1133.4
    LC = 1635.8
    RH = 597.45
    MEL = 418.30
    sc_EDY = 3.6318e+05
    mc_EDY = 7.7850e+05
    lc_EDY = 1.0042e+06
    rh_EDY = 4.1212e+05
    MEDY = 3.1541e+05
    Tcp = 2939.5
    x = 0.4402
    y = 0.4033
    z = 0.1565
    x10 = 0.4492
    y10 = 0.3907
    z10 = 0.1601
    u = 0.2530
    v = 0.3477
    v_ = 0.5216
    L = 69.703
    a = 17.433
    b = 42.993
    C = 46.393
    h = 67.928
    Ra = 51.375
    Rf = 56.838
    duv = -7.4044e-04

Evaluate several spectral power distributions with resulting |Y| = 1000:

lam = 380:780;
spec = ciespec(lam,{'FL2','A','D65'},1000);
data = speceval(lam,spec)

See also: ciespec

Result:

data =

  scalar structure containing the fields:

    X =

        991.46   1098.41    950.42

    Y =

       1000   1000   1000

    Z =

        673.15    355.87   1088.61

    SC =

       0.5083   0.2542   0.8173

    MC =

       1.2814   1.1743   1.4558

    LC =

       1.6160   1.6567   1.6289

    RH =

       0.9250   0.8308   1.4497

    MEL =

       0.7558   0.6575   1.3262

    sc_EDY =

        621.92    311.01   1000.00

    mc_EDY =

        880.17    806.60   1000.00

    lc_EDY =

        992.05   1017.06   1000.00

    rh_EDY =

        638.04    573.09   1000.00

    MEDY =

        569.90    495.81   1000.00

    Tcp =

       4225.1   2856.0   6501.8

    x =

       0.3721   0.4475   0.3127

    y =

       0.3753   0.4075   0.3291

    z =

       0.2526   0.1450   0.3582

    x10 =

       0.3793   0.4511   0.3138

    y10 =

       0.3673   0.4059   0.3310

    z10 =

       0.2534   0.1429   0.3552

    u =

       0.2202   0.2560   0.1978

    v =

       0.3331   0.3495   0.3122

    v_ =

       0.4997   0.5243   0.4684

    L =

       67.672   69.997   64.084

    a =

       5.1118e+00   1.8313e+01  -5.7970e-03

    b =

       2.1367e+01   4.6138e+01   9.2311e-03

    C =

       2.1970e+01   4.9639e+01   1.0900e-02

    h =

        76.545    68.351   122.128

    Ra =

        64.250   100.000   100.000

    Rf =

       70.208   99.996   99.997

    duv =

       1.8626e-03   7.1936e-06   3.2145e-03

References