Anyone who has spent some time shopping for aftermarket lighting knows the struggle of differentiating between legit sellers who have tested and can confirm the features they advertise, and sketchy copycats who drag-and-drop nice-sounding lines from other brands into their own listings with zero understanding of the terminology. When it comes to brightness, the go-to measurement to boast in these days seems to be Lumens. But what are Lumens anyway? How about when you across brightness being described in Lux or Candela? What’s the difference between these forms of measurement, and how much should each one matter to you?
Without getting all scientific and long-winded, here’s what you should know about Candela, Lux, and Lumens:
“How far away can I be from the light source and still be able to see it?”
Candela is commonly often used to measure lighting used as laser pointers. That’s because Candela measurement has nothing to do with how well the lighting disperses or fills up a space – it’s just the visible intensity of the light source.
So do you need to worry about Candela when buying a new pair of LED headlights? Not really – it’s more important for headlights to fill up a given space with plenty of light and to brightly illuminate surfaces. On the other hand, if you’re buying an amber emergency light for an official security vehicle, Candela count will be very relevant – you’re not trying to usefully give off much illumination, but you do want that flashing light to be visible from far away.
“How much light does this bulb give off?”
Lumens are the most common form of measurement you’ll see and probably the easiest to understand. It’s the amount of visible light given off by your bare bulb. The greater the Lumen count, the more visible light emitted, and the more space you can illuminate (emphasis on “can” – you’ll have to keep reading to find out how shitty engineering can affect this). Covering 25% of the bulb will cause your Lumens to go down by 25%. Covering half the bulb will cause your Lumens go down by half. It’s really that simple.
“How brightly will this surface area be lit?”
Lux is Lumens per square meter. Think about it – a light may shine intensely on a wall when held right up to it, but if you back the light up to cover a wider part of the wall, the light will naturally be softer when dispersed over more surface area.
If you’re buying new headlights or taillights, Lux should definitely matter to you – many sub par lights on the market have a high Lumen count but a low Lux measurement because they don’t have focused beam patterns. Whether that’s caused by badly designed housing or poor engineering in any other part of the light, having incorrect beam patterns causes light projection to look foggy and weak in actual use – aka it wouldn’t project strong, focused light on the wall or car in front of you. What’s the point of rocking new LED headlights that are ultra-bright “on paper” but scatter light so much that they’re not real-life functional?
If you’ve stuck with us until now, congrats, you now know more than the average Joe about the different brightness measurements relevant for different kinds of lighting. Moral of the story is that Lumens aren’t everything, and if you ever have suspicions about some shady seller copying a major brand’s Lumen count, ask ‘em about the other measurements that are relevant – chances are, they won’t know as much as you do.