How Much Light Do I Have? Footcandles, Lumens and Lux

If you’ve ever sat down to attempt the purchase of new lights, one of the first questions you have is “how bright are these things?” and “are they bright enough for my lighting rig?”

While demo rooms and online videos can give you a rough estimate, neither is accurate enough to show you how the light will look in your space with your other lights.

So how in the world do we compare different lights, and how can we know if it’s going to be bright enough?

Well, we’re going to have to rely on some measurements for this.  So go grab a light meter, and let’s dive in!

How Bright is “X” New Light Anyways?

When we’re looking at product spec’s sheets, there are 2 different types of brightness measurement that we can take into account.

The first measurement is lumens or the total amount of light output by the source.  This is a measurement of all the light put out across the whole beam of the light, and is useful when comparing the overall brightness of a fixture, but not all that useful for knowing if your stage is going to be bright enough.

The 2nd type of measurement is foot-candles/lux, which measure how bright the light is at a certain point.  This is the measurement you need when you are figuring out how bright your stage needs to be, and this is what you measure with a handheld light meter.

Foot-candles and lux actually measure the same exact thing – lux is the international standard while foot candles are the English standard measurement.  (Think meters vs. feet).  1 Foot Candle = 10.76 lux

So, for a rough estimate, you can simply divide your lux by 10 to get foot-candles.  It’s not the totally scientific answer, but it will get you close!

LED’s – Where It All Gets Complicated!

Now forget everything that I just told you. 🙂

Okay, so I am kidding (a little bit), but the truth is, the light-measurement waters can get tricky when you add LEDs into the mix.  As long as we are comparing different incandescent/arc/fluorescent fixtures to like fixtures, comparing footcandles or lumens is no problem.

But when manufacturers measure LED’s, the measurements can really begin to vary.  I hate to say this, but the output measurements of different LED fixtures aren’t really comparable.  Many manufacturers publish really poor measurements, only giving you total lumens or lux/foot-candles at a certain distance.  Sometimes, they even change up that distance per fixture, so you can’t even compare different units on paper.

When you’re trying to compare LED’s on paper, your best bet is to do a common-sense comparison of a few factors:

  1. How many LED’s does it have and at what wattage?
  2. What is the beam angle and field angle?
  3. How many lumens does it put out?

Then, take the information that you come up with and compare them to units you know and have seen in real life.

What Else Matters?

When you’re looking at possible lights to purchase, you need to first decide what features are important to you, and then compare similar lights that are on the market.

Does having zoom matter to you?  What color temperature do you need?  How much power do you have available for this new light?  If LED, how many different colored LED’s do you desire?  RGB, RGBW, RGBA or more?

While brightness can be compared across different types of LED units, it’s not going to be accurate to compare different types of LED lights on the same scale.

Use the questions above to evaluate what you want to purchase and take the time to do a thorough comparison before you buy!

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