What is the best Color temperature?

and What value reduces the most Blue light

A lot of users asked me what is the best value of Iris for blue light reduction. Well in this article I’m going to look at exactly this with measurements.

This will be helpfull for users of other software products like f.lux, Redshift, SunsetScreen, Night Shift and Night Light.

The Android Twilight and Night mode use different algorithms than Color temperature. Twilight is like the Iris Overlay mode and Night mode is like the Iris Groot color scheme.

I made a 10 measurements of the display from 6500K to 1200K since this is the format that is universal to all blue blocking softwares and I think is enought.

6500K is screen with no color changes at all. This is perfectly calibrated screen.

1200K is the lowest value of f.lux, Redshift, Night Shift and Night light. Actually Redshift can go down to 1000K, f.lux to 800K, SunsetScreen to 500K and Iris to 0K, but this is irrelevant.

The bellow measurements are the same for all software products. No matter what anyone tells you all this softwares do the same thing with color temperature. They may do it with different algorithms, but the end result is the same.

6500K – 100%

At 6500K this is how the color graph looks like. You see that blue light is even more than all other colors and this is the first reason that this value is bad for your sleep and for your eyes.

We will just use this measurement as comparission to other values and as how normal displays emmit colors.

The height of the blue part of the graph shows the amount of blue light emitted.

The height of the green part of the shows the amount of green light emitted.

The height of the red part of the shows the amount of red light emitted.

It’s important to know that most softwares reduce also the green light at low values and red light is untouched at all values.

Thus to select the best value we will need to select the value with lowest blue light and highest green light, but green light should also be reduced for best eye protection and sleep.

5970K – 90%

Close to the light of Mercury vapor light lamp and Cloudy sky light the color graph looks like this

5440K – 80%

Close to the light of Daylight metal halide lamp (HMI) and Average noon light the color graph looks like this

4910K – 70%

Close to the light of Late morning and Early afternoon light color graph looks like this

4380K – 60%

Close to the light of Cool White Fluorescent lamp (CFL) and Mid Morning and Mid Afternoon light the color graph looks like this

3850K – 50%

Close to the light of Standart Clear metal halide lamp and Later Afternoon light the color graph looks like this

3320K – 40%

Close to the light of Halogen light lamp and Evening light the color graph looks like this

2790K – 30%

Close to the light of Household tungsten light lamp and Sunset light the color graph looks like this

2260K – 20%

Close to the light of High pressure sodium light lamp the color graph looks like this

1730K – 10%

Close to the light of Candle light the color graph looks like this

1200K – 0%

Close to the light of Ember light the color graph looks like this


To save you the thinking here what all these results mean. The lowest blue light will be at 1200K or bellow, but this is actually not the best setting.

At 1200K a lot of the green light is reduced and the screen may be hard to read.

Best value for sleep and blue light reduction is 1900K or Candle light.

Iris is using 3400K for the night and 5000K for the day. The reason for this is because new users get shocked by the big changes to their screen colors and can’t handle the transition from really bright screen to 1900K.

Start with 5000K during the day and 3400K during the night. After several months gradually switch to 1900K all the time for best health.

Try to get more full-spectrum sunlight and go outside from time to time to produce good amounts of melatonin.

Thank you for reading this article,
Daniel – Founder of Iris

Posted in Articles, Blue light