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Lux vs Lumens: Everything You Need to Know

Tim Dennis

Ever bought a light bulb, and wondered about lux and lumens? The chances are that your light bulb moment never came, and you're still thinking about it now.

More and more advanced technology is causing a rise in the popularity of smart light bulbs. Also, projector screens now dominate our own home cinema entertainment spaces.

Yet few are aware of the importance and difference between lux vs lumens. So allow us to help.

So to find out more about these metrics, we've defined them side by side. That way, you can better understand how the two relate to each other.

What Is a Lux?

A lux unit (symbol: lx) is a measurement of illumination. Something like sunlight or the light from a lamp will fall on a surface.

The closer to a light source, the more light hits the surface. Thus the lux number will increase.

Because it's such a variable number, lux ratings often come with conditional specifications. An example of this is "500lx at 2m distance".

It gives customers an idea of how much light appears to the human eye. That's because lumens are only relative to the physical amount of light outputted.

What Are Lumens?

The term comes from the Latin lumen, meaning "light." a lumen is a measure of light intensity. It's used in lighting design to compare the intensity of light through various surfaces.

Lumen measurement is often used in specifying the brightness of light bulbs. It also measures light fixtures and illumination technologies.

A lumen is an actual physical unit of measure, and it's not as variable as lux. It's based on the fact that light energy radiates from a source in all directions. Thus making it ideal for comparing different lamps and lighting technologies.

Lumens provide a more accurate measurement of how much light you're getting. A lumen reading allows better comparisons of lighting types.

Lux has no such standardisation, given that it's dependent on subjective perception. Thus it can vary depending on factors like the wavelength of the light.

How Many Lumens Are In a Lux?

You can use a lux vs lumens calculator to work out a comparison for more complex numbers.

For example, let's say that you have a bulb with a certain lumens rating. How many lux will that be? Well, 1 lux equals 1 lumen per meter squared.

For reference, the light intensity of indirect daylight equates to about 10,000lx. A reading taken in direct sunlight can be up to 100,000lx, and while on an overcast day, it can be as low as 1000lx.

When to Use Lux vs Lumens

The simplest way to explain this is that if you measure the light output from the source, measure in lumens. But if you measure how much of that light reaches a surface, that's measured in lux.

Thus, it's safe to say that one can't exist without the other. Yet depending on your use case, one is more dominant than the other. We've given the perfect example below of a home cinema projector to illustrate how the two occur side by side in the same setting.

Lux vs Lumens Projector Example

Suppose you're buying a projector and a white projector screen. Then you'll want to know how many lumens the projector outputs. The more lumens there are, the brighter the image will be.

That's useful to know, depending on your use case. Outdoor projectors require much higher lumens outputted than indoor due to the strength of natural daylight. That provides enough variation for a more flexible setup.

For example, the lux measurements, "1000lx at 2m", help understand where best to place the screen. Imagine you have room for up to a 120" projection in your living room. It might be that your room is quite bright and the projector doesn't output enough lumens to reach the other side of the room.

Moving it closer will increase the lux rating. While this makes the screen size smaller, the image becomes clearer and brighter, making it easier to see.

How to Measure Lux vs Lumens

Measuring lux vs lumens is not too difficult. There are different lux meters and lumens meters on the market, but the best way is to get a portable light meter to measure lux and lumens.

Many light meters are designed specifically as lumen meters, while others can measure lux and lumens. That's when you need to know what you're measuring so you can look into the relevant specifications. You can also use lumens to distance chart to work out the lux rating.

If you are struggling to figure out how to measure lumens, measuring the actual light in a room is a good way to get accurate numbers. For context, if you're thinking of buying a projector, you should have one handy as well. That way, you'll be able to compare and work out what's best for you easily.

Using Lux vs Lumens

While the science behind lux vs lumens is complex, the concept is much easier to comprehend. Lux focuses on the receiver, or input, of light, whilst lumens focuses on the producer, or output, from the light source itself.

If you're trying to figure out how much light you'd need from a projector, then you'll need to know how many lumens the projector is outputting by itself. Thus, the above examples should help you make a more informed decision on your next lighting purchase.

For all your lighting needs, shop online today and see how we can brighten up your life!

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