Technical resource
Choose the distribution for the surface you need to light
A narrower beam concentrates light over a smaller area; a wider distribution spreads it. The visible result also depends on mounting height, aiming, surface reflectance and delivered lumens. Compare the photometric file for the selected optic and test the result in the actual layout. Wattage and nominal beam angle alone cannot establish the quality of the lighting.
Distribution and geometry
Spot, flood, oval, asymmetric, wallwash, graze, zoom and framing describe different tasks—not options available on every model. Compare at identical mounting height, target, distance and aiming; record surface reflectance. An elliptical distribution needs both axes and its orientation.
Beam versus field angle
Beam angle normally describes the 50% peak-intensity boundary; field angle describes the 10% boundary. Neither alone establishes uniformity or glare. Use the exact optic/CCT photometric file and include any honeycomb, snoot or barn doors in the calculation and BOM.
Project examples to calculate
Artwork needs target size and conservation constraints; double-height spaces need distance and glare review; shelving needs vertical coverage. Wallwash requires setback and spacing; facade columns, trees and paths require spill and aiming checks. These are calculation briefs, not simulated LUMIBRIGHT photometry.
What specifiers ask
How do narrow and wide beams change spacing?
A narrow optic needs closer spacing to avoid scallops between pools of light, or wider spacing when each fitting is deliberately lighting one object. Set spacing from the calculation for the chosen optic and mounting height.
How does the optic change contrast and glare?
Narrow beams raise contrast, which makes an object read as emphasised. They also concentrate luminance, so shielding matters more. Wider optics lower contrast and generally appear softer.
Which exact optics are available?
Optic availability is model specific. The article table on each family page lists the beam angles actually supplied for that model — do not apply the family range to every fitting.
What files should be requested for a calculation?
Ask for the IES or LDT file for the exact model and optic, plus the CCT and CRI of the tested sample.
Related pages
Ask for the photometric files for your shortlisted optics
Send your reflected ceiling plan, room dimensions or lighting schedule. Include the project location, stage and required date so the team can confirm suitable models and the documentation available.