Kelvin, lumens, watts, and CRI are printed on lighting packages everywhere. Once you know what those numbers actually mean, choosing the right light for your home, garage or workshop gets much easier.
Color temperature is one of those things hiding in plain sight on nearly every light bulb and fixture package.
A 2700K light looks warm and yellowish. A 5000K light looks cooler and more blue-white. Strangely enough, the higher-temperature light is the one we describe as “cool.”
The reason goes back to the color of a heated object called a blackbody. As its temperature rises, its glow shifts from red and amber toward white and then blue. Modern LEDs don’t operate at thousands of degrees, but their color is compared to that theoretical glow using Correlated Color Temperature, or CCT, measured in kelvins.
There are several other lighting numbers worth understanding:
Kelvin (K) describes the color appearance of white light.
Lumens (lm) measure the amount of visible light produced.
Watts (W) measure electrical power consumption, not brightness.
CRI (Ra) is the Color Rendering Index and describes how accurately colors appear under a light source. The traditional Ra score averages several standard color samples. A CRI of 80+ is generally suitable for everyday lighting, while 90+ is especially useful where wood tones, paint colors, finishes, and detail matter.
For decades, incandescent bulbs trained us to associate wattage with brightness because bulbs of the same technology produced fairly predictable light output:
LED technology broke that old relationship. Modern LEDs can produce the same amount of light while using dramatically less power.
2700–3000K works well for comfortable living spaces. 3000–4000K is useful in kitchens, bathrooms, and utility areas. 4000–5000K is popular for garages, workshops, and task lighting.
And don’t put too much faith in package names such as “Soft White,” “Bright White,” or “Daylight.” Those terms vary between manufacturers. The Kelvin number is the more useful reference.
Lighting has also evolved from firelight and candles through gaslight, incandescent, fluorescent, and today’s increasingly efficient and controllable LEDs. Selectable color-temperature fixtures, high-CRI LEDs, smart lighting, and dim-to-warm technology continue to make lighting more adaptable.
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Video Summary
AI Generated
This video provides a comprehensive guide to understanding modern lighting terminology, helping consumers move past confusing marketing labels to make informed purchasing decisions. It explains the technical differences between color temperature, brightness, and color fidelity, while offering practical recommendations for different living and working spaces.
Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
Have you ever walked into the home center
of your choice to go buy some lighting and
you got almost assaulted by all sorts of terminologies,
color temperatures, cool white, you know,
bright white, all that sort of stuff that can
be really confusing until you understand
a few basic things.
We're going to walk you through it.
Stay tuned.
All right, using this infographic,
I'm going to decode all of that for you.
So from now on, you can walk in there confidently
and get exactly the lighting you need.
So let's just walk through this.
Step by step.
So first of all, there's a basic evolution of lighting.
I mean, all the way back from campfires to gaslight,
incandescent, which many of us are really familiar with,
and some of the retro lighting is like that.
But that was all a high heat lighting.
Then you ended up with fluorescent type of lightings
or tube type of lighting that occurred.
And then now we are at a place where present and beyond,
LEDs have really landed and are making a big mark for a couple reasons,
one of them being
energy savings, the other is color appearance that's tunable.
The second thing to know is what is color temperature?
This was always very confusing to me.
When I'd walk in there, I'd go, well,
what does that have to do with anything?
Does that mean when I turn on a bulb,
if it's a lower temperature, that's how hot the bulb's
Or if it's a higher one.
No, not at all. All it is is keying back to the appearance of light.
Way early on, scientists used what was a device called a blackbody,
and they would heat it, and it would glow different colors.
So lower temperatures,
it would glow more in the amber, yellow, orange range,
something we might call warmer.
And the hotter the blackbody got, the closer it got to bluish.
And ultimately white light.
So the higher the color temperature expressed in Kelvin is,
the cooler the light is, which is inverse.
The hotter the black body was, the cooler the light.
Yes, closer to sunlight,
whiter blue spectrum versus cooler light, red, orange spectrum.
So keep that in mind.
Low number, warm.
High number, cool.
A good way to see the kelvin differences is right here in my own shop.
You can see some of the lighting here.
So this particular, which is a garage light,
is running about 5000 kelvin. It's non-adjustable.
It doesn't have a slider switch. It's that color
or none at all. So we've got that in there.
The second one is an adjustable color one,
and that is set at about 4000 kelvin.
And you can see it's a little bit yellower.
These have got those adjustable fans are very efficient
and the last one that we're gonna have you take a look at
...is a fading technology, a CFL, a compact fluorescent light.
And these put out a much lower, probably around 2500,
right above Rob over his shoulder in the back.
There's one in the ceiling right there.
You can see that as a much yellower light than
the other two that you have taken a look at.
There's a good practical illustration of the differences between...
Kelvin temperatures.
All right, so now let's just talk about,
since we've already talked about lower
and higher Kelvin numbers,
let's just talk about the bulb numbers themselves.
Kelvin's already been covered, but what lumens?
Lumens is just the amount of visible light.
We'd call it brightness.
Watts is the amount of electricity that was used.
Now notice in modern lighting, LEDs,
they give more lumens per watt.
So we can no longer equate
Wattage with brightness,
that is an old measurement and sometimes is used as shorthand to say
lower watt would be a dimmer bulb, higher watt would be higher.
But that's mingling systems.
The next one is the CRI, the Color Rendering Index,
and that is how true the color is.
of what it's putting out against what it's called.
So, if it has a high number,
it's high fidelity to the color it's being called out.
This is bright white. Yes, it's a very white bulb.
If it has a lower index number, the fidelity is not good.
They could call it, in marketing terminology, bright white or cool white.
But when you measure the light with a meter and all that,
that's not what is being cast onto objects.
So the higher the number, the better fidelity.
And the reason that's important if you're doing photography,
architectural rendering, paint colors, all sorts of things,
you've got to know what those colors look like under that light.
So the next thing is to pick the right light for your space.
So these are again Kelvin numbers, lower numbers.
If you like home comfort,
you're going to use that lower range, up to 3000 Kelvin.
If you need something that is more utility-based, need better lighting,
clear lighting that is functional,
then you're going to be 3000 to 4000 Kelvin.
And if you're doing garage
and workshop areas like what we're in right now,
4,000 to 5,000 Kelvin lighting does a great job of giving you great
detail without being too harsh and being hard to look at items, okay?
So names can be misleading on the packaging,
and that's because manufacturers use different terminology
to describe the lighting they're providing.
So you'll see terms like soft white, bright white, daylight, etc.
Well, trust the Kelvin number, not the marketing name.
That tells you what it is you're buying.
So look for the Kelvin number to begin with.
Okay, as we talked about a little bit earlier about watts,
here's an area in the infographic
that just tells you about the old watts
versus modern lumens that are produced by LED.
So you can see the different equivalents,
rough equivalents of those to get an idea of what you're getting now
with this new lighting system.
Where's this all going in the future?
Well, first of all, selectable.
And a lot of that is happening now.
Some of the switches on the side of things, shop lighting in here.
I can choose whether I want lower or higher Kelvin temperatures.
The second thing is highly indexed bulbs
that allow for true color fidelity
for very precise settings that we talked about.
Architectural renderings, color management, paint colors,
all of that sort of thing where you need true color.
Being shown on the camera or to the viewer when they come in
and the lighting source is adjusted for that.
The next one is smart bulbs and we're already seeing
a wide range of that happening already with smart homes
and smart lighting systems.
But that isn't going to stop.
A lot of innovation is going to happen there.
We're going to see some cool things happen there.
And lastly is dimmed to warm ambience where
You can change the ambience
of the bulb depending on what time of day it is,
the setting, all that, and some of that exists now.
But watch for more of this developed.
This is really cool stuff.
If you found this to be helpful, but we covered a lot quickly,
you can go and download this whole graphic and make it your own.
Just simply go
to go to dirtfarmerj.com forward slash decoding light.
Download it and you'll enjoy it.
Now, if you're at this video,
lighting is something that is important to you.
Well, you may be needing to rewire an old lamp.
Check out this episode where we show you how to do that safely.
And yes, polarity matters.
And there's certain safety protocols
that will demystify all that as well.
You'll enjoy what you see.
Until the next time,
this is Dirt Farmer Jay going to take a walk in the light.
