Open Air Tutorials: What is a Lumen?

Anyone who has shopped for a digital projector will have encountered the word lumen without explanation, as if everyone has already agreed on what it means. In simple terms, a lumen measures how much light a projector emits — how forcefully it throws illumination into the world.

Once upon a time this was called candlepower. A single unit — a candela — was based on the light of one candle made from exactly 0.167 troy pounds of whale blubber, burning at a precise rate for eight hours. Modern outdoor cinema no longer requires a background in marine harvesting. Today the candela is defined as the luminous intensity of monochromatic radiation emitted at 540 terahertz with a radiant intensity of 0.001464128 watts per steradian — precise, if not immediately useful at a campsite.

For practical purposes: more lumens means a brighter projected image. What matters is choosing a projector that produces a clear, watchable image given the ambient light at your venue. The right lumen rating depends on screen size, throw distance, and how much surrounding light you can control. Our support team is happy to help match a projector to your setup.