For those who use f.lux, what are the best settings for day and night?

Hi, Mr. Bighiu and thanks for the question.

I decided to write you public response because if I just write you something small it will not be enough and if I write you something long via e-mail I will just waste my time which I value a lot.

So today I receivedΒ this e-mail

I wanted to respond to the Reddit thread but it was locked for inactivity so I will try to give you my answer here πŸ™‚

The question is: What are the best K values for day and night?

I wrote about this in this publicationΒ What is the best Color temperature? but let’s look into this question in more science.

Here are links to some medical researchers for daytime blue light exposure:

Blue-enriched white light in the workplace improves self-reported alertness, performance and sleep quality.

A Comparison of Blue Light and Caffeine Effects on Cognitive Function and Alertness in Humans

So the results of the studies are correct, blue light improves mood and alertness during the day but it’s not that simple.

The first thing is that monitors don’t emit full-spectrum light.

In the graph above you can see how different Daylight is from LED light.

Our bodies are made to get full-spectrum Sunlight and increasing only the blue light is like not balanced diet.

You need balance, I don’t want to go into much details about this but the light emitted from the Sun and the light emitted from the monitors is just different.

Looking at the graph above you see that the most balanced light is around 4000 K, but 4000 K from software like f.lux and Iris is not real 4000 K.

It’s only close interpolation based on gamma calculation, so with Iris or f.lux on 4000K the graph looks close to this

You see that even on the best values there are still dips which don’t emit light at this frequency. This is because of Physics of the LED.

The recommendation should be to spend your time during the day outside so the Sun can glow your body.

The light into the eyes may produce the biggest melatonin response but just like coffee, it’s not healthy in the long run.

In the long run, a lot of Blue light into the eyes causes Macular Degeneration. It doesn’t matter if it’s daytime or nighttime exposure, blue light is the most powerful visible light and it enters deep into our retina.

You know that UV light causes permanentΒ damage, but look at this graph

Blue light is the closest visible light to the UV and the effect of it are not so strong but in the long run, it’s like looking directly into UV light.

We can go even further by looking into a full light spectrum and notice how close UV and blue light is to X-rays which cause permanentΒ damage to our cells and make them mutate.

Yes, you have a small chance to mutate like in X-men but most probably if you expose yourself to too much radiation you will just die.

Yes, you are not going to die from blue light, but we are just not made to see a direct light. Most of the time we look at reflections and this is why reading a book outside causes us less eye strain.

So I and many doctors (I am not a doctor or anything I just have talked to a lot of them) are to avoid blue light from the monitor all the time and to spend some time outside on direct Sunlight to get your mood and melatonin levels in check.

I personally use 5000 K during the day because otherwise my screen is too dark and this causes me eyestrain.

During the night I use 3400 K and during the late night around 2700 K.

You may notice that this are also Iris default values because I try to do the software perfect for myself so new users don’t have to think about it but just use it.

If you need a boost to your energy you can increase the blue light. Iris actually supports higher than maximum blue light levels for this but I personally don’t like this.

You can see this values in the extended values and it looks like this

I noticed that in the new beta of f.lux you can go to 100 000 K, but it’s just overkill and this value is not actually 100 000 K, I don’t know why it’s added.

I have heard from several doctors that they use Iris at 0K whole day which looks like this

But again I think it’s overkill.

Like everything it’s about balance but using 6500 K orΒ normal colors during the day is definitely not the best option and I don’t think it will be beneficial in the long run πŸ™‚

CEO Iris


Posted in Articles