Photometric Standards

Q: What is the proper orientation for my luminaire?

A: The proper orientation of your luminaire depends on the type of distribution it produces. There are 3 possibilities for the vertical distribution of light:

• Direct - single hemisphere, light directed downward
• Indirect - single hemisphere, light directed upward
• Direct / Indirect - light is directed in both the lower and upper hemispheres

The following lists the proper luminaire orientation:

• Direct - aim center of beam toward -Z in the CAD drawing coordinate system
• Indirect - aim center of beam toward +Z in the CAD drawing coordinate system
• Direct / Indirect - aim the center of the downward beam toward -Z in the CAD drawing coordinate system

The following lists the proper vertical angular range you should use in Photopia:

• Direct - 0 - 90 degrees, for example (0(5)90)
• Indirect - 90 - 180 degrees, for example (90(5)180)
• Direct / Indirect - 0 - 180 degrees, for example (0(5)180)

There are 4 possibilities for the horizontal distribution of light:

• Symmetric - the distribution of light is the same in all horizontal planes
• Quadrilaterally Symmetric - the distribution of light in one quadrant (90 degrees) of lateral angles can be mirrored about the X and Y axes to describe the distribution in all quadrants
• Bilaterally Symmetric (Asymmetric) - the distribution of light in 180 degrees of lateral angles can be mirrored about one axis to describe the entire distribution
• Completely Asymmetric - there is no symmetry in the horizontal distribution

The proper orientation of your luminaire in the X-Y plane depends on both the horizontal distribution type and your location in the world. There are different standards for North America and for the rest of the world. See the pictures below to for the proper orientation of your luminaire and for the proper range of angles you should specify in Photopia.