Smart LED dimming curves: Linear vs. logarithmic

Smart, cloud-connected LED light bulbs will let you dim the lights on a 100-point scale -- but those 100-point scales vary from bulb to bulb. Some dial the lumens down in linear fashion, with 50% of the total lumen output at the 50% setting, for instance. Others use a logarithmic dimming curve that dims down faster for more of a perceivable change in brightness from setting to setting. With a bulb like that, you might only get 25% of the total lumen output at that 50% setting.

And, as it turns out, the science of how we see brightness supports the logarithmic approach, but different bulbs do it differently. Click here to read more about dimming curves and the difference they can make in the way you light your home, or scroll through this gallery for a close look at the way several of the most popular affordable smart bulbs handle dimming.

Let's start with our first example of a bulb that uses a logarithmic dimming curve, the C by GE Life LED. The dotted red line represents the "target" that you're asking for when you set it to a specific setting on that 100-point scale (again as an example, 50% of the lumen output at the 50% setting and so forth). The blue line is the bulb's actual light output at that setting, as measured in the CNET Lighting Lab.

As you can see, the brightness drops down a lot faster than the linear target line. That's because you need more of a change in brightness at settings above 50% or so in order to actually see a difference from setting to setting. The logarithmic approach addresses that by "fast-forwarding" through the bulb's dimmable range at those upper settings, then leveling out at the bottom.

The Cree Connected LED uses a logarithmic dimming curve, too -- but it's a really weird one. Instead of "fast-forwarding" at the top of the bulb's dimmable range, it actually slows things down, and dims down even slower than the target line. That means that you won't see much of a difference in brightness at all between any of the settings above 50%.

Meanwhile, the Eufy Lumos Mini LED follows a linear dimming path. While linear dimming curves don't offer much of a perceivable difference in brightness among those top-half settings, they do tend to offer more of a difference between settings at the very bottom of the bulb's dimmable range, because the dimming curve doesn't flatten out at the bottom like you get with a logarithmic bulb.

See what I mean? With this logarithmic Lifx LED, the difference between the 1% setting and the 20% setting is just 21 lumens. With the linear Eufy LED from that last slide, the difference between those two settings is 177 lumens.

Here's another bulb with a logarithmic dimming curve and a very flat bottom of the range, the Philips Hue White LED. The difference between 1% and 20% is only 22 lumens. The difference between 1% and 10%? Just 2 lumens!

Here's the dimming curve for TP-Link's Kasa KB100 LED. It takes a linear approach. (It lifts away from the target line a bit there because the bulbs cool down a bit as I dim them down to take my readings -- with less heat, the brightness starts to rise very slightly. I did my best to keep that X-factor at bay during my tests, but it's somewhat unavoidable.)

Finally, here's the Sengled Element Classic LED, now simply called the Sengled Soft White LED. It's another option with a linear dimming curve.

For more on the differences between these two approaches to dimming -- including some, ahem, illuminating photos that'll show you what the difference actually looks like -- check out my full explainer post on the topic.