Lighting 101 – Part 2

In my most recent post, I wrote about layers of light.  Think of it as a lighting outfit for your room, house, etc.  What I mean by that is general lighting is the clothing you’re wearing, minus accessories.  Accessories like belts, scarves, shoes, glasses, even a hat are the task lighting, and jewelry is the accent lighting.
























Speaking the Language of LEDs (Light Emitting Diodes)

Once you have a sense of the overall outfit, or in the case of lighting, how you want your space to look with the updated lighting and the location of fixtures, then what?

A decorative fixture can look great on its own, but if you’re not getting the light that you expected from it, then what?  When we replace lightbulbs, there are so many options for what to buy;  often fixtures don’t come with bulbs and if you are using LEDs what do you need to know?  If you are doing a project with an electrician, how do you speak their language?

Lumens, Color Temperature, and CRI – what are those?

There are three main attributes to consider when lighting with LEDs, which most of us use throughout our homes: Lumens, Color Temperature and CRI.

First, let’s start with Lumens, or how bright the light is that a bulb produces.  If you look at the bulb packaging shown below, you will see brightness on the bottom right of the box, above energy cost (450 lumens).

Secondly, Color Temperature, which is the color of the light (from warm to cool) that a bulb produces, and it’s on the bottom left of the packaging below, next to wattage (2700K).

And finally, the Color Rendering Index (CRI) measurement, or how well the light emitting from a bulb shows the true color of an object that it’s focused on, and this is to the right and above the image of the bulbs on the packaging below (90 CRI).

And these three are referenced on just about any LED lightbulb package you buy, but what do they mean and why are they important?

Do you want to become a lighting geek?  Then read on…to decode more about LED bulbs.

What happens when you are buying a new fixture?

What if you are buying a new fixture?  When you review the details of any fixture, there are quite a number of specifications, for example; look at the list for the fixture below, and see four categories just devoted to bulbs; often fixtures’ specifications only list maximum wattage.  How do you translate that to lumens?  And what does bulb base mean?


First, Lumens are the measurement of how much light is being emitted by any light source.

Fixture Specifications – Bulbs

When selecting bulbs for a fixture, look at the fixture specification for bulb base type or bulb type, as well as wattage, typically referring to an incandescent bulb (even though LED bulbs are measured in lumens); you can find the equivalent brightness for LED bulbs and it is much less wattage than for incandescent bulbs that produce the same number of lumens.  Talk to whomever you are ordering the light fixture from for confirmation.

Wattage v. Lumens

Wattage is a measure of the energy a lightbulb uses, instead of lumens, which, again, is how much light output there is from any lightbulb.  So if a specification lists 100 watts for a light bulb, what kind of LED bulb could you choose?

A 100 watt incandescent provides about 1600 lumens; and the LED equivalent uses only 25-28 watts. The chart below shows how lumens translate to both incandescent and LED wattage, and you can see how much lower the energy use is for LEDs.

More about Bulbs

For the bulb’s base type, talk with your lighting company;  “E” (Edison) type bulbs are most common, as they are screwed into the socket and the most common size of those is “E26” with the 26 the width of the base in millimeters. Too much information?  See the chart below for shapes, base types and more (and on our packaging above, the bulb type is “A19” with and Edison base).  There are also fixtures that come with integrated LEDs, these are typically strips of diodes, and they cannot be replaced without replacing the fixture.


Dimming is also a way to control bulb light output and I recommend it for just about every fixture!  LED sources need different dimmers than incandescents, so talk with your electrician or lighting company about your best options.

Color Temperature

Secondly, Color Temperature is the color of the light emitted from a light source; this selection is up to you and it’s about how warm or cool you want the light to be in your room and/or home, because that affects how objects (walls, floors, furniture, accessories) appear to you.

What you need to know about the color temperature of LED bulbs is at 2000K to 3000K (K stands for Kelvin, which is the scale used for measuring thermodynamic temperature) a light bulb emits a warm glow, similar to incandescent bulbs.  As you move up the Kelvin scale, the warm or orange glow moves into the bright white color ranges (6000K for example) with 9000K to 10,000K emitting a blue light.  Daylight for example, as you can see on the chart below, is from 4800K to 6000K or so.  In residential settings, most LED bulbs are in the 2700K to 3000K warm range (with whiter light being better for task areas like kitchens and baths – up to 4000K depending on client preference).

How does my space look with lighting depending on color temperature?

Why is the color temperature important when choosing LED bulbs? Color temperature emitted from a light source can change how we perceive the color of what the light is focused on.

What if you are repainting a room, for example?  How does color temperature affect that?

For example, if you are repainting a room, something to consider when choosing colors is that warmer paint colors are enhanced by warmer lighting conditions (red, orange and yellow), while cooler ones, like blue and green colors are enhanced by cooler lighting conditions.  If you choose an LED bulb with a color temperature of 2700K (which is warm, and very similar to incandescent bulbs) it will enhance red, orange and yellow colors in the room, with the blue and green range appearing muted;  if you move toward the natural light range to 4000K (4800K to 6000K is the range for natural light), blue and green colors will be enhanced and the warmer colors will appear duller.   It is important to test out how you perceive the different color temperatures, particularly if you are making a change.

If you like how your current room looks with your existing fixtures with their current bulbs, choose the same color temperature bulb for any new fixture.  If you want a change, try out some new bulbs in different color temperatures!  You probably already have noticed changes in how your interiors look going from natural daylight into artificial light.  And if you are adding lighting to areas where you perform tasks, like kitchens and baths, the general recommendation is to select color temperatures from 3000K to 4000K. See the image below for moving from warmer light on the left, to cooler light on the right.

CRI – the Color Rendering Index – Higher on the scale is better.

And finally, the Color Rendering Index (CRI) measurement tells us how colors look under an artificial light source, when compared   to being in natural sunlight.  Colors look most vibrant when they are seen in natural light, across the full color spectrum.   LED bulbs can produce better (or worse!) color rendering.

CRI is on a scale of 1-100, 100 being what you would see under natural light conditions, showing the color of whatever is being lit at its most vibrant.  What should you look for in CRI measurements?

A CRI measurement of less than 80, is not considered good, colors can be drab, and it may be difficult to distinguish similar colors from one another.  A CRI of 80-90 is better, and often okay for commercial settings.  A CRI above 90 is very good, with good color rendering, providing depth in the colors and is what you want for residential applications. (As you get closer to 100, the CRI becomes even better, providing more depth of color, etc.). The apple all the way to the right is the best rendered!

By understanding the details of LEDs, not only can you replace bulbs in an informed way, you can buy the bulbs that will work in your space without multiple trips back to the store for new or existing fixtures!