If you’re like us, you probably make your lighting decisions based on gut feel. You like the way certain lights look, and not others. Sometimes it’s hard to put your finger on why you like one light and not another.
Most lighting resources are either overly simplistic (think “soft white”) or overly technical (what would you imagine if you were told the light you were considering had the following specs: 1000L, 2700K CCT, 90 CRI, 40 Degrees?) Even if you know the terms, it can be hard to translate that into the look and feel of a light source.
This post aims to demystify the physics of lighting in order to help you better understand how to manage the lighting in your space. Let’s dive in.
Brightness is generally the first thing you’ll notice about a bulb. It’s important! Just think about the last time your pub turned up the lights at last call. I bet you noticed the brightness then.
Light output is the total amount of light generated by the bulb in any direction.
The unit of this metric is the Lumen (lm). 1300 lm would be a very bright bulb – about a 100-watt equivalent, whereas 320 lm would be a very dim bulb, about a 20-watt equivalent.
Light output is not exactly brightness, as we would normally think of the word, because this measures all the light coming from the bulb, not just the light shining in a particular direction. So a more focused bulb may appear brighter even though it is producing less light.
Some bulbs shine light in all directions – like this typical incandescent bulb:
Some focus their light in a particular direction with the use of mirrors, like this one:
How tight or narrow the focus determines the bulb’s beam angle (sometimes also called beam spread). Beam angle is measured in degrees from center as shown below. The classic “spot” beam is typically between 10 and 15 degrees from center, while a “flood” light generally casts light 40 degrees from center in either direction.
This is where light output and beam angle intersect. If two lights have the same light output (lumens), the one with the tighter beam angle will appear brighter to the human eye. This is because the tighter beam angle focuses the same amount of light into a smaller space. Similarly, if two bulbs have the same beam angle, the one with the higher light output will appear brighter.
This is why a flashlight can appear so much brighter than a regular desk lamp, even though the total lumens from a desk lamp is actually much higher.
To measure light intensity, lighting designers use a metric called center-beam candle-power, which measures how much light is produced in the center of the beam.
Color and Light Quality
Ok, we can’t avoid getting technical now. Let’s talk about what color is for a moment. A color is a specific piece of the light spectrum – one little slice of the rainbow, if you will.
To understand color, let’s follow some light from your lamp to your eye. Imagine you’re looking at a red dress in a retail store. How is the color actually generated in your eye? First, the light is generated by the lamp and travels toward the dress. Let’s assume it’s “white” light, so it contains the full visible spectrum. The light travels toward the dress and eventually makes contact. When the white light gets there, all of the light except that red gets absorbed. The red is special. Instead of getting absorbed, it gets reflected. From there, that red light travels to your eye, where your brain registers it as the color red.
So why is the dress red? In a very technical sense, because it only reflects red light. Every other color just gets absorbed and doesn’t bounce back to the eye. But since the dress is reflecting the light, if the light coming out of the lamp didn’t have red, that dress wouldn’t look so wonderful.
Color rendering is essentially a way of measuring how much of each color the bulb is producing. If it’s producing an even amount of each color, it will render any color well. If the light from your bulb only contains a few colors, then most colors won’t show up properly. Remember – that red dress is reflecting the red light from your lightbulb. If there’s no red light coming from the bulb, it won’t look red!
Fluorescent bulbs work by mixing just a few colors – so the colors in-between often get lost. That’s why things don’t look good under fluorescent light. Check out the mix of colors in a fluorescent bulb below – all those colors in between the spikes are getting lost!
When LEDs were first made available, many performed quite poorly when rendering colors, especially in the red part of the spectrum. But as LED technology has improved, color rendering has improved dramatically. High quality LEDs now produce a distribution of visible light that is much smoother than the graph you see above and much more closely approximates a traditional halogen. No particular colors are coming out more heavily than others, which means that the colors in products are much more truly reflected.
To see the difference in practice, go check out one of our customers to see just how amazing their products look.
Color temperature refers to the relative amount of red and blue in the light produced by the bulb. Light with more red seems and is referred to as “warmer”, whereas light with more blue is “cooler” or “crisper”.
LEDs come in all sorts of color temperatures. Many people associate LEDs with “cool” light, but that doesn’t have to be the case. Good LEDs are available in a variety of color temperatures, and most of Building Hero’s clients use warm LEDs in their spaces.
Color temperature is measured in degrees Kelvin (which is a system like Celsius or Fahrenheit, but it’s for scientists). Confusingly, a lamp gets “warmer” as its color temperature goes down. And vice versa, a lamp gets “cooler” as its color temperature goes up.
Geek note: The reason this is called color temperature is because it refers to the light output of a black-body radiator that has been heated to a certain temperature. So when we say that a lamp has a color temperature of 2700 degrees Kelvin (K), that means that it has the same light output of a black-body radiator that has been heated to 2700 K.
The main thing to take away from this article is that light quality is multifaceted. Many different qualities in a given bulb interact to give a space a type of feel. Many of our customers intuitively understand what they want in their space, what they like and don’t like, but lack the language of lighting design to choose that perfect bulb from the millions of LED products out there.
For instance, many of our customers tell us they dislike the blueish light associated with fluorescent bulbs – unaware that you can get “warm” fluorescent bulbs. But these “warm” bulbs will still give off subpar light because they are not covering the whole color spectrum. In other words, it’s not their color temperature, it’s their color rendering that’s the issue.
We hope this post will help you get exactly what you want out of your lighting. If you’re considering LED lighting for your space, and want to work with people that deeply understand how to achieve the look you desire in your space, get in touch today!