Creating scene illuminant structures

ISET scenes represent the scene spectral radiance and the scene illuminant. The spectral radiance is a hypercube of data, that is a spectral power distribution (vector) at each scene point.

The simplest illuminant is a single spectral power distribution. In this case the illuminant is constant (the same) at every point in the scene.

Alternatively, the scene illuminant can be a hypercube with the same size as the scene spectral radiance. In that case, we call spatial-spectral . The illuminant is potentially different at every point in the scene.

See also: illuminantCreate, s_sceneIlluminantMixtures, s_sceneIlluminantSpace

(c) Imageval Consulting, LLC 2012

Contents

ieInit

Create a blackbody illuminant structure 5000 deg Kelvin

illum = illuminantCreate('blackbody');
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')

Create a blackbody illuminant at 3000 deg Kelvin

wave = 400:1:700;
illum = illuminantCreate('blackbody',wave,3000);
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')

D65, 200 cd/m^2

luminance = 200;
wave = [];  % Defaults
illum = illuminantCreate('d65',wave,luminance);
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')

Equal energy

illum = illuminantCreate('equal energy',[],luminance);
e     = illuminantGet(illum,'energy');
w     = illuminantGet(illum,'wave');
mn    = mean(e(:));

vcNewGraphWin;
plot(w,e); grid on
xlabel('Wavelength'); ylabel('Energy')
set(gca,'ylim',[0.9*mn,1.1*mn]);

Equal photons

illum = illuminantCreate('equal photons',[],luminance);
p     = illuminantGet(illum,'photons');
e     = illuminantGet(illum,'energy');

w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('photons')
mn    = mean(p(:));
set(gca,'ylim',[0.9*mn,1.1*mn]);

vcNewGraphWin;
plot(w,e); grid on
xlabel('Wavelength'); ylabel('Energy')

CIE standard illuminant C

illum = illuminantCreate('illuminant C',[],luminance);
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')

Monochrome at 555 nm

illum = illuminantCreate('555 nm',[],luminance);
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')

CIE D65 but sampled over a different wave range

illum = illuminantCreate('d65',400:2:600,200);
e     = illuminantGet(illum,'energy');
w     = illuminantGet(illum,'wave');

vcNewGraphWin([]);
plot(w,e,'ks-'); grid on
xlabel('Wavelength'); ylabel('Energy')

Interpolate and overlay the two different sampling resolutions

illum2 = illuminantSet(illum,'wave',400:5:700);
e     = illuminantGet(illum2,'energy');
w     = illuminantGet(illum2,'wave');

hold on;
plot(w,e,'ro'); grid on
xlabel('Wavelength'); ylabel('Energy')

Fluorescent illuminant

illum = illuminantCreate('fluorescent',400:5:700,10);
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')

Tungsten

illum = illuminantCreate('tungsten',[],300);
p     = illuminantGet(illum,'photons');
w     = illuminantGet(illum,'wave');

vcNewGraphWin;
plot(w,p); grid on
xlabel('Wavelength'); ylabel('Photons')