Specifies standard illuminants.
| IG_ILLUMINANT_UNKNOWN | Unknown illuminant. |
| IG_ILLUMINANT_DAYLIGHT | Daylight illuminant. |
| IG_ILLUMINANT_FLUORESCENT | Fluorescent illuminant. |
| IG_ILLUMINANT_TUNGSTEN | Tungsten illuminant. |
| IG_ILLUMINANT_FLASH | Flash illuminant. |
| IG_ILLUMINANT_FINE_WEATHER | FineWeather illuminant. |
| IG_ILLUMINANT_CLOUDY_WEATHER | CloudyWeather illuminant. |
| IG_ILLUMINANT_SHADE | Shade illuminant. |
| IG_ILLUMINANT_DAYLIGHT_FLUORESCENT | DaylightFluorescent illuminant, D 5700 - 7100K. |
| IG_ILLUMINANT_DAY_WHITE_FLUORESCENT | DayWhiteFluorescent illuminant, N 4600 - 5400K. |
| IG_ILLUMINANT_COOL_WHITE_FLUORESCENT | CoolWhiteFluorescent illuminant, W 3900 - 4500K. |
| IG_ILLUMINANT_WHITE_FLUORESCENT | WhiteFluorescent illuminant, WW 3200 - 3700K. |
| IG_ILLUMINANT_STANDARD_A | StandardA illuminant. |
| IG_ILLUMINANT_STANDARD_B | StandardB illuminant. |
| IG_ILLUMINANT_STANDARD_C | StandardC illuminant. |
| IG_ILLUMINANT_D55 | D55 illuminant. |
| IG_ILLUMINANT_D65 | D65 illuminant. |
| IG_ILLUMINANT_D75 | D75 illuminant. |
| IG_ILLUMINANT_D50 | D50 illuminant. |
| IG_ILLUMINANT_ISO_STUDIO_TUNGSTEN | ISOStudioTungsten illuminant. |
| IG_ILLUMINANT_OTHER | Other illuminant. |
See IG_IP_DCRaw_camera_to_sRGB_matrix_calculate for more details.