The Carex Day-Light Classic and Sky are two of the best-selling SAD lamps on the market, so I thought I would do a thorough scientific review of them so that you can confidently choose the best one for you.

In this review, we’ll be going over the pros and cons of each, the real total lux output (which was surprising), as well as things like color temperature, flicker, magnetic fields, and more!

So let’s get into it!

Build and Features

Here’s a quick breakdown of the stats and features of these lamps:

halo happylight light therapy lamp
luxe happylight light therapy lamp
Adjustable Brightness
Brightness Settings
Adjustable Color Temperature
Lux @ 12"
Circadian Light @ 12"
Coupon Code
OPTIMIZE15 for 15% off
OPTIMIZE15 for 15% off

As you can see the Sky appears to be the clear winner from our tests, however, it does something a bit odd which we’ll go over in some graphs in the lux measurement section later on.

Both of these lamps are fairly large and won’t fit on a regular office computer desk.

front shot of carex daylight sky and classic

The Classic is however a little bit larger than the Sky, so keep that in mind if you’re low on space to begin with.

There are push buttons on both lamps that can be used to adjust their height up or down, as well as the angle of the lamp head.

Overall I found the Sky model a bit easier to adjust. The Classic has this vertical adjustment bar that isn’t quite as responsive and tends to get stuck sometimes. It’s not terrible, just not as fluid.

Each lamp has only two brightness settings, high, and low, so using them is pretty simple. They both have a 6.3 ft power cable, but since the Sky’s cable is attached to the bottom of the lamp, it technically has the longer each of the two.

back shot of carex daylight sky and classic power cables

I actually ran into an issue where I couldn’t plug the Classic into the outlet near my dining room table without an extension cable, whereas the Sky was able to reach the same spot without one.

Now with all that out of the way, let’s talk about the lux output.

Lux Measurements and Comparisons

Both of these lamps claim, like many others, to put out that fabled 10,000 lux, however unlike most of the others, these publicly specify the distance at which this is achieved. Which is 12”.

So like all of the other lamps we’ve tested, we put them 1 foot away from our spectrometer and took readings over one hour to see what they put out, and the results were a bit surprising…

testing the daylight sky

At first, both lamps put out right around 10,000 lux, but within a minute they were both exceeding 10,000 lux by quite a bit.

The Classic

Let’s start by looking at the Classic:

lux graph of carex daylight classic

You can see that it starts out at around 9,000 lux but quickly climbs to 13,000 before averaging out at about 12,500. That’s 25% brighter than advertised! Which is a pleasant surprise in the world of light therapy lamps! These things usually underperform, so that’s nice to see.

Looking at the Sky, however, things get a little bit weird…

The Sky

Here’s the graph from our first test, with reading intervals of one minute:

lux graph of carex daylight sky

Weird right? I told you. As you can see this looks nothing like the lux graph from the Classic.

The Sky does start off at around 10,000 lux again, but quickly climbs to almost 16,000 lux, and then…. Jumps around like a madman the whole time. It does average out to around 14,500 lux which is once again almost 50% brighter than advertised! So once again I’m pleasantly surprised by this.

But this brightness variation thing is weird, and since I thought maybe it was a glitch in my spectrometer software, I did the test again, but this time at 30-second intervals.

So here’s that graph:

lux graph from second test of carex daylight sky

Still, just as weird, but we get a bit more detail this time. We can see that the brightness variation sort of calms down after 20 minutes or so, but then just after the 40-minute mark, it starts to oscillate again before calming down again.

All I can assume is that the power circuitry on this lamp isn’t performing as it should be, I’m not sure if this was just my lamp or if this is a manufacturing flaw in the Day-Light Sky, but it’s there.

Now, we have used this lamp several times in the morning and we’ve never noticed any fluctuations in brightness, so if you’re worried about that, I wouldn’t be. It feels like one steady brightness during use.

Overall though, when it comes to light output, the Sky is the more effective lamp. Especially since it’s putting out a slighter cooler color temperature, which we’ll talk about in a minute.

Speaking of brightness fluctuations, that brings me to our next topic, which is flicker.


LEDs nowadays rarely flicker noticeably, however, almost all of them have what we call invisible flicker as the AC is converted to DC.

Some people seem to get headaches, or eye strain from invisible flicker, and the lower the flicker rate the higher the potential is for these issues.

Unfortunately, both the Classic and Sky lamps have some pretty bad invisible flicker.

These LEDs are flickering at a pretty low 120 Hz or 120 times per second, with a depth of around 20%, which is fast enough to escape your visual perception, but slow enough that it can be observed using slow-motion video capture.

You can check out our YouTube video review to see that.

I don’t seem to be affected by this kind of flicker, I like to avoid it if I can, but it doesn’t really bother me.

This does fall into the High-Risk category of the IEEE’s flicker standard.

carex classic light therapy lamp flicker risk graph
Flicker risk for the Classic
carex sky light therapy lamp flicker risk graph
Flicker risk for the Sky

So if this is something you like to avoid, we have flicker data for all the lights we test in our light therapy lamp database.

Color Temperature

Now let’s talk about the actual quality of the light!

This part is my favorite. I like colors. I’m a simple man.

Both of these lights claim to be emitting a color temperature of 4000K. During my testing, I clocked the Classic in at 4050K and the Sky at 4200K, so they’re actually pretty close to spec, which isn’t usually the case.

4000K is warmer than most of the lamps I’ve tested and also a bit closer to morning sunlight so some of you might find the light from these a bit more visually comfortable in the morning.

Now of course they both advertise “full-spectrum” light, but unfortunately, they are anything but.

carex day light sky light therapy lamp spectral power distribution graph
Here’s what the spectrum from the Carex Day-Light SAD lamps looks like

I measured a CRI of 78.7 for the Classic, and 78.3 for the Sky, both of these scores are pretty bad from a color rendering perspective.

For example, they both had an R9 score of around 20, meaning they output very little red light. A low CRI score isn’t the biggest deal breaker for a light therapy lamp, but now you know if that’s important to you.

Glare Ratings

One thing to take note of is the lux per square inch between these two is quite different. While the Sky does give off more light than the Classic, its illumination area is also smaller, which means it appears quite a bit brighter.

The Classic is putting out 110 lux per square inch, while the Sky is sitting at around 180 lux per square inch. So if you have issues with light sensitivity, the Classic may be the better option.

Light Therapy Database Button

Magnetic Fields

I suppose the last thing I can touch on with these is that I checked for magnetic fields, and there were none to be found. If you get right up next to them there is a small 1-2 mG field that opens up but you’ll never be that close so it’s no concern.


So closing opinions?!

After using and testing both of these lamps my pick goes to the Sky model, it’s brighter, more effective, and it actually appears to be cheaper both on Carex’s website and on Amazon, so it sorta seems like a no-brainer.

As far as the odd brightness oscillation goes, it doesn’t really concern me that much. It’s weird, but probably not really detrimental in any way. But if it does bother you, the Classic model is still a great tried and true light therapy lamp.

Of course, these both made it into our best SAD lamps article!

Carex Day-Light Sky



  • Cheaper and more effective than the Classic model
  • Longer power cord range than the Classic due to placement


  • Has some odd lux fluctuation issues, but you can’t tell during use
  • More glare on this one than the Classic due to its smaller size and higher output
  • Some low-frequency flicker

Use coupon code OPTIMIZE15 for 15% off

Carex Day-Light Classic



  • An effective output of 12,500 lux at 12″
  • Steady brightness output unlike the Sky model


  • 20% less lux output than the Sky model
  • Costs more than the Sky
  • Power cord location limits range
  • Some low-frequency flicker

Use coupon code OPTIMIZE15 for 15% off

That’s it for this one! Hope it was helpful!

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        1. Well there’s nothing really special about them in that regard. Some are better than LEDs and some aren’t, it just depends on total power output at the end of the day.

          For example the Alaska Northern Lights NorthStar uses fluorescent lights and is among one of the most powerful and effective SAD lamps out there. Then again some others like the HappyLight Full-Size is less impressive as it’s power output is much lower.