### 44.13 Light and Illumination

`GSL_CONST_MKSA_STILB`

  The luminance of 1 stilb.

`GSL_CONST_MKSA_LUMEN`

  The luminous flux of 1 lumen.

`GSL_CONST_MKSA_LUX`

  The illuminance of 1 lux.

`GSL_CONST_MKSA_PHOT`

  The illuminance of 1 phot.

`GSL_CONST_MKSA_FOOTCANDLE`

  The illuminance of 1 footcandle.

`GSL_CONST_MKSA_LAMBERT`

  The luminance of 1 lambert.

`GSL_CONST_MKSA_FOOTLAMBERT`

  The luminance of 1 footlambert.