Type I–V light distributions: choosing an optic

What the category tells you

Assess distribution alongside mounting height, spacing, orientation and luminaire output. Two optics in the same category can produce different results on the same site.

Types I, II and III

Type I has a narrow, elongated lateral distribution that can be a starting point for linear routes. Types II and III allow other relationships between the width of the lit area and the luminaire position to be considered.

For streets and roads, selection depends on the complete geometry. Avoid choosing an optic solely by lane count or a general width rule.

Type IV

Type IV can be considered for perimeter positions where forward throw is required. Actual backlight and glare depend on the optic, orientation and accessories. The category alone does not guarantee an absence of light behind the luminaire.

Types V and VS

Type V describes a circularly symmetric distribution; Type VS describes a square symmetric distribution. They can be assessed for open areas, but suitability depends on luminaire locations and the activities within the space.

A symmetric distribution does not automatically provide uniform lighting. Check the result using the planned luminaire arrangement.

Compare candidate optics

Request the photometric file for the exact configuration. Provide a dimensioned layout, mounting positions and heights, lighting criteria and site boundaries. Include restrictions on obtrusive light and the maintenance assumptions.

Compare the numerical results required by the project, not just the rendered image. Graphic views help interpret the distribution but do not replace checks of levels, uniformity and glare where applicable.

If height, tilt or orientation changes during installation, review the calculation before assuming the intended performance will be maintained.