In [1]:

```
import colour
print(sorted(colour.ILLUMINANTS_SDS.keys()))
```

As per *CIE publication CIE S005/E-1998*: [2]

CIE Standard Illuminant A is intended to represent typical, domestic, tungsten-filament lighting. Its spectral distribution is that of a Planckian radiator at a temperature of approximately 2856 K.

CIE Standard Illuminant Ashould be used in all applications of colorimetry involving the use of incandescent lighting, unless there are specific reasons for using a different illuminant.

The *CIE Standard Illuminant A* has the following range and increments:

In [2]:

```
colour.ILLUMINANTS_SDS['A'].shape
```

Out[2]:

In [3]:

```
from colour.plotting import *
```

In [4]:

```
colour_style();
```

In [5]:

```
plot_single_illuminant_sd('A');
```

The CIE Illuminant B is a daylight simulator intended to represent direct noon sunlight with a *correlated colour temperature* of 4874 K.

The *CIE Illuminant B* has the following range and increments:

In [6]:

```
colour.ILLUMINANTS_SDS['B'].shape
```

Out[6]:

In [7]:

```
plot_single_illuminant_sd('B');
```

The CIE Illuminant C is also a daylight simulator but intended to represent average daylight with a *correlated colour temperature* of 6774 K.

The *CIE Illuminant B* and *CIE Illuminant C* are poor approximations of any common light source and deprecated in favor of *CIE Illuminant D Series*. Both are deficient in their spectral distribution in the ultraviolet region which is important for fluorescent materials.

As per *CIE 015:2004 Colorimetry, 3rd Edition*: [3]

Illuminant C does not have the status of a CIE standard but its spectral distribution, tristimulus values and chromaticity coordinates are given in Table T.1 and Table T.3, as many practical measurement instruments and computations still use this illuminant.

The *CIE Illuminant C* has the following range and increments:

In [8]:

```
colour.ILLUMINANTS_SDS['C'].shape
```

Out[8]:

In [9]:

```
plot_single_illuminant_sd('C');
```

*CIE Standard Illuminant A*, *CIE Illuminant B*, and *CIE Illuminant C* spectral distributions are shown here altogether:

In [10]:

```
plot_multi_illuminant_sds(['A', 'B', 'C']);
```

In [11]:

```
# Plotting *CIE Standard Illuminant A*, *CIE Illuminant B*, and * CIE Illuminant C* with their normalised colours.
plot_multi_illuminant_sds(['A', 'B', 'C'],
use_sds_colours=True,
normalise_sds_colours=True);
```

*CIE Standard Illuminant A*, *CIE Illuminant B*, and *CIE Illuminant C* chromaticity coordinates plotted against the Planckian Locus into the *CIE 1931 Chromaticity Diagram*:

In [12]:

```
plot_planckian_locus_in_chromaticity_diagram_CIE1931(['A', 'B', 'C']);
```

Notice how the isotemperature lines are not perpendicular to the *Planckian Locus*, the *CIE 1960 UCS Chromaticity Diagram* with perpendicular isotemperature lines is better suited for *correlated colour temperature* computations:

In [13]:

```
with colour.utilities.suppress_warnings(python_warnings=True):
plot_planckian_locus_in_chromaticity_diagram_CIE1960UCS(['A', 'B', 'C']);
```