Understanding LED Lighting: How Brightness is Measured with Lumens and Lux

The different ways to gauge the brightness level of your LED flashlight

When buying an LED flashlight I always found it hard to know how bright it was going to be. Of course the brighter the better, generally speaking but when buying a light that looked like it had a lot of LEDs or the LED bulb was a good size and it ended up being dull, it was a huge let down. I used to judge an LED light's brightness by how many bulbs it had or how big the bulbs looked. It seemed logical, but I soon learned that there is more to knowing how bright an LED light is going to be than what it looks like.

In short, when looking to buy an LED flashlight you can see what the Lumen rating is, ensure it’s a reputable brand and see if they mention the beam distance. 100-400 lumens are good for working in the garage and seeing darker areas, 500-1000 lumens really helps outdoors like night hiking or camping, and also comes in handy when changing a flat tire in the dark. Anything above 1000 lumens will start getting heavier, bulkier and require quite a bit of battery. Ensure you have brightness modes so you can choose when to go full brightness or lower to save battery. The key here is ensuring the brand is reputable, anyone can say anything about their lights brightness so beware.

Another notable feature to look for is if the LED flashlight has a beam that is adjustable from narrow to wide. This can come in handy if needing to see a wide area near you or a small spot far away. Battery life is going to be a big factor, especially if you’re going on a multi-day trek. Some flashlights have rechargeable batteries that aren’t replaceable, they last longer than traditional batteries but you may need to carry an external battery pack to charge them up on long treks. Keep in mind how many AA, AAA or larger batteries your flashlight needs because it will impact both how long the flashlight can run and how much you’re going to have to spend on batteries.

See if they mention the weather sealing against rain, impact resistance, if the light has multiple brightness modes, red-light or blue-light features and battery indicators. Versatility is key so you can get the most use out of your flashlight.

Measuring an LED lights brightness with Lumens

Lumens measure the total amount of visible light of an LED light, representing its brightness. Lumens focus on the light output itself, making them a more accurate way to gauge how bright a light will be.

To measure lumens, a light source is placed in an integrating sphere, which captures and spreads the light evenly over its surface. Sensors inside the sphere detect the light intensity from all directions. The collected info is then processed to calculate the total amount of visible light that is emitted, giving its lumen rating.

A higher lumen number means a brighter light, while lower lumens indicate a dimmer output.

The problem with lumen ratings is no one is necessarily regulating what lumen rating is claimed by a specific product. Sure, some manufacturers can work with a testing laboratory to get an accurate rating but unfortunately in many cases it is either estimated or just plain made up.

I’ve seen regular sized flashlights claiming to reach 10,000 lumens or even a preposterous 100,000 lumens! Keep in mind a car headlight is around 2000 - 4000 lumens. In order to reach 100,000 lumens, think along the lines of a stadium light, you would need a massive light system, heat dissipation and a huge amount of power. Now imagine something that powerful tucked into a handheld flashlight and you can see how ludicrous their claims are.

In my YouTube video here, I try to gauge an LED light's brightness by shining the light against a white wall and comparing different lights to each other.

Measuring an LED lights brightness with Lux

An alternate way to measure an LED light's brightness is through lux which is a measurement of how much light illuminates a specific area, essentially describing the brightness of light on a surface. It's defined as the amount of light (in lumens) spread over a square meter. The higher the lux, the brighter the light appears in that area.

To measure lux, a lux meter is commonly used. This device captures light hitting a specific surface and gives a reading in lux. For example, direct sunlight can reach about 100,000 lux, while typical office lighting is around 300 to 500 lux.

Lux is particularly important in lighting design and safety standards. It helps determine how well-lit a space is, ensuring that areas like workplaces, streets, and homes have the appropriate lighting levels for both functionality and comfort.

Lux isn’t typically used to gauge an LED flashlight's brightness, instead lux measures the amount of light illuminating a surface. Lux takes into consideration not just the brightness of the LED bulb but also the total area that is illuminated. The distinction means that a 500 lumen LED bulb projected over a wide area with a lens can be a lower but more wide spread lux rating while that same bulb can reach a higher than 500 lux rating if the light is focused to a smaller area.

Personally I like flashlights with a texture pattern so it’s easier to grip, I always appreciate hoops or grooves where I can secure the light to something else and I would love to see a flashlight that can take multiple types of batteries (could be achieved via additional inserts or attachable battery packs). I’m dreaming a bit but hey, you never know.

It is the wild west when it comes to LED lighting brightness and it’s difficult to know how bright a light source is going to be. Pricing isn’t always based on quality or brightness, so it really is an uphill task. Purchasing from a reputable brand will go a long way and keeping an eye out for the features that make sense for you will be key.