LOR (Light Output Ratio)

LOR stands for Light Output Ratio. LOR is calculated by dividing the total light output of the lighting fixture by the light flux of inside the lamp. This ratio defines the performance level of the lighting fixture. It shows us how much light is lost in lighting fixture.

Light output ratio is the most important factors when the lighting designers choose a lighting fixture. Light output ratio is a percentage value and if this ratio is high, lighting fixture has better performance (more light and more energy saving)

Light produced inside a bulb exits in all directions except for its screwed base. Some of the light that comes from different directions will be lost when a bulb inserts on a chandelier, lamp shade or a table lamp. There will be losses in light even if the reflective surface is perfect.

For example, if you mount 1000 lumen bulb to a 70 LOR lighting fixture, you will have 700 lumen light. 30 percent of light will be trapped in lighting fixture.

LEDs are directional lighting sources. Because of that light loss is minimum and light output ratio is higher than other lighting fixtures.

Ulbricht sphere or goniophotometer is used to measure the LOR value of the light fixture. A lamp with a certain brightness mount on a light fixture and the total lumen of light fixture recorded. The total lumen of the light fixture is divided by the lamp’s lumen. Therefore, you will find the LOR value. If the brightness of the lamp is unknown, the lamp should be measured with the same measurement technique.

LOR percentage of the light fixture can be read from the photometric data of light fixture (IES, LDT)

Some of the manufacturer claims that their light fixture has 100 % LOR value. However, it is not technically possible. There will be losses in light even if the reflective surface is perfect.

If you do not consider the LOR value during the design phase, a dimmer environment may be created than expected at the end of the application. If you have a knowledge about the LOR value, you will obtain more realistic results.