# Take note of how brightness makes you feel

I just moved into a new apartment and am working on getting my lighting set up. Like [polyamory](https://www.lesswrong.com/w/polyamory) and [group housing](https://www.lesswrong.com/w/group-houses-topic), [lighting](https://www.lesswrong.com/w/lighting) is one of those things that rationalists sometimes approach differently from the rest of the population, and are arguably ahead of the curve on. If there were a running list[^tt4u71shyui] of [shit rationalists say](https://www.lesswrong.com/posts/p5jwZE6hTz92sSCcY/son-of-shit-rationalists-say), something about lighting should probably be included.

From what I understand — and I don't have the best understanding[^168515tu081] — the standard rationalist take on lighting goes something like this:

*   Typical rooms aren't very bright; maybe 100-500 lux.
*   That is about 100x less bright than the outdoors.
*   You should aim for a brightness of at least 1,000 lux, but it's hard to go overboard.
*   Brighter rooms improve productivity and mood. Two things that are quite important, especially as you multiply the benefits across time.
*   There's solid evidence that brightness helps people with SAD, but like autism, SAD [probably isn't a discrete thing](https://lorienpsych.com/2020/10/30/ontology-of-psychiatric-conditions-taxometrics/). It probably exists along a spectrum and how much you benefit from extra brightness plausibly depends on where you are on this "SAD spectrum", with people in the middle of the bell curve plausibly getting very tangible benefits.
*   There's also a reasonable evolutionary argument to be made: if we evolved in environments ~100x brighter than our indoor offices, maybe our dimmer indoor offices aren't quite optimal.
*   Getting a setup of bright lights ultimately isn't too expensive (in terms of various types of costs including dollars, time, and space).

I don't really have much of an opinion on any of this. It all seems plausible, but not so plausible that I'm super convinced that increasing brightness is definitely going to bring meaningful benefits to the average person, and something that the average person should invest in.[^lo151ndgky]

But here's the thing: I don't think the effect it has on the average person matters very much. What matters is the effect that it has on *you*.

Ok, so how can you tell what the effect it has on you is? Well, here's an idea: download a brightness measuring app on your phone, use it in various locations as you go about your life, and take note of how different levels of brightness make you feel.[^reravcz54k]

I just did that and so far it's been pretty cool. I downloaded [this app](https://apps.apple.com/us/app/lux-light-meter-pro/id1292598866) on my iPhone and it seems pretty solid. [This post](https://www.photoworkout.com/best-light-meter-apps/) recommends some other apps.

I'm at a coffee shop right now. This is the booth I'm sitting at:

![image.png](https://res.cloudinary.com/lesswrong-2-0/image/upload/v1774906265/lexical_client_uploads/tvwqn1yyjlajwnianmvr.png)

The brightness ranges from like 200-500 lux depending on where I point my phone[^ktzx85q2jh]. But over here by the window it's more like 1,000 lux, and I feel notably more "awake" and happy.

![image.png](https://res.cloudinary.com/lesswrong-2-0/image/upload/v1774906861/lexical_client_uploads/swbvloq02kdw7srwtk9c.png)

After walking around this building a bit, I got a bunch of other data points. For example, the coffee shop is adjacent to the lobby of an office building, and in that lobby I got some readings in the 600-700 lux range.

I plan to continue to do this over the next few days and am hopeful that in doing so I'll develop a good idea of how different levels of brightness make me feel. Then once I know how different levels of brightness make me feel, I think I'll be well positioned to determine what sort of investment I want to make into the lighting in my new apartment.

One caveat is that the effects of brightness might be subtle. Too subtle for me to successfully introspect on. Maybe brightness affects me in ways that I simply don't have the ability or skills to actually notice. That does seem like something of a risk, but:

1.  I suspect that my ability to introspect is good enough to get me in the right ballpark.
2.  I can mitigate the risk by upping my estimate of the appropriate lux level by a couple hundred points. Like, if 700 lux *seems* like the sweet spot, I can adjust upwards and assume that 1,000 lux is the *actual* sweet spot.
3.  I don't see a better way of measuring how brightness affects me. I'm sure any better techniques would be more time/money/effort than I would find worthwhile.

Another caveat is that most indoor lighting just isn't very bright, so if you want to see how it feels to be in 1,000+ lux levels of lighting, I suppose you'll probably need to do this outdoors. Or if you're in the Bay Area, maybe you could find some nerd with a lumenator to cowork with.

In Portland, OR at about 5pm, the image on the left was about 1,700 lux and the sunny spot on the right was about 6,000 lux. 6,000 was way too bright. 1,700, I dunno, I don't think I noticed much of a difference between that and the ~1,000 lux in the coffee shop.

![Screenshot 2026-03-30 at 5.05.38 PM.png](https://res.cloudinary.com/lesswrong-2-0/image/upload/v1774915546/lexical_client_uploads/ma39ze3rblhxqgzgohkm.png)

Ultimately, what I propose is very quick, easy and cheap: download an app, take some brightness readings, and take note of how different levels of brightness make you feel. The potential benefits seem pretty big[^8qoow7gj1qh]. Potentially even *huge*.[^sedxr20xu7]

So then, I think my proposal is likely something that lots of people should do, especially the types of people who will end up reading this post. [Cheap experiments](https://www.lesswrong.com/posts/cbfiXhEXfvZRHAzNC/experiments-as-a-third-alternative) are the best!

[^tt4u71shyui]: Someone please pursue this! 

[^168515tu081]: I read through a handful of LessWrong posts on lighting, talked with a relatively knowledgeable friend about it a bit, and prompted a bit. 

[^lo151ndgky]: One big hesitation I have is along the lines of the efficient market hypothesis and "absence of evidence is evidence of absence". If lots of people really can benefit a fair amount by increasing the brightness of their indoor lighting, I dunno, I'd expect a variety of things.I'd expect people like Andrew Huberman, Peter Attia and Tim Ferris to discuss it. This "Ask Huberman Lab" AI thing doesn't seem to indicate that Huberman discusses brightness and I don't recall anything from Attia or Ferris. I'd also expect academic research to have some solid findings, and I'd expect rationalists to cite this research. I'd expect companies like Brighter to have some sort of whitepaper or FAQ discussing such research findings as well.Yes, I've read Inadequate Equilibria. I know any such researchers or whatever need to be properly incentivized to do such research. I don't have the strongest read on the culture within academia, but I feel like there'd be some pretty nice "prestige points" to be earned with such research. Additionally, I'd think that organizations that care a lot about productivity like big tech and the military would find a way to scratch the back of such researchers.None of this is super confident. Maybe medium confident. Just thinking out loud. 

[^reravcz54k]: While you're at it, it's also probably worth taking note of how different color temperatures make you feel. I'm less enthusiastic about this though. Most people will probably choose something slightly warm to neutral colored, maybe 3,000 to 6,000 K, and from what I could tell, it doesn't seem like differences in that range are likely to have too large an impact. 

[^ktzx85q2jh]: Lux is a measure of how much light is being received whereas lumens measure how much light is being emitted. This article has a helpful graphic that illustrates the difference. 

[^8qoow7gj1qh]: As a very quick Fermi estimate, suppose that better lighting improves your productivity by $1/hr. And suppose that you spend 20 hours a week working in your home office. Over ten years, that's something like $1/hr * 20 hrs/week * 40 weeks/year * 10 years = $8,000 worth of extra productivity. 

[^sedxr20xu7]: What if you are a high impact person who gets more like a $10/hr boost in productivity? What if your work improves the lives of many other people? And what about the mood boost benefit? I can see improved brightness having a six or even seven figure benefit for certain productive and/or altruistic people.