Imagine that we are looking directly at the cross-section (end) of a pendant-mounted linear direct/indirect lighting fixture in an open office. (Note that this article focuses on Type A photometry, which covers indoor general light fixtures, not Type B photometry, which is used for floodlighting and other outdoor fixtures.) All the other items on the report, such as zonal lumen distribution, fixture efficiency and fixture spacing criteria are derived from the numbers in the candela chart’s table.

What are the basics that we need to know, so we can properly read and interpret photometric reports? The most important items on the report are the candela chart and the candela distribution curve, which give us a picture of the fixture’s distributed lighting pattern. Specifically, we can determine how the light is distributed, how efficiently it is distributed and how likely it is to produce glare or unwanted patterns. What a report says about a lighting fixture can be used to predict how it is likely to perform in a given application and help us choose the right fixture. Commonly available for specification-grade lighting products, these reports are found on the catalog sheet. In the real world, we have photometric reports. Then, the manufacturer would hire people to work there for a while and conduct a postoccupancy survey on their satisfaction with the lighting. In a perfect world, a lighting manufacturer would respond to interest in one of their products by assuming the cost of installing samples in an exact mockup of the actual space being designed.

Led photometric diagrams