Visual Display of Brightness (Lux)


Awesome points and I whole heartily agree with that assessment. This is part of the reason I wanted to discuss this topic to see what others think and how best to render those values. I don’t want people to get lost in the main goal and that is regardless of LUX, Candles, etc.

My expectation is to see the value provided by the Sky. In turn someone really smart and creative like Brian can relay that same value into what ever display method. For me seeing a Sun / Moon lighter vs darker makes sense keeping in mind the LUX value would be displayed for the user. So in time a person could relate what ever value to the image they see.

Having more choices is great and if Brian decides to go one direction vs WF vs Other great! :+1:


I agree. I just think we shouldn’t get to far into the weeds with this. It could only confuse things more for the masses than help them understand the weather, which is the whole point of a weather station for 99% of users.



Great discussion, appreciate the collaborative spirit and collective insight. There are two distinct outputs here: 1) empirical data values in standard format that can be consumed, used, displayed in any way by others, and 2) how to display or communicate the empirical data values to the layman in our simple Smart Weather app.

#1 is obvious. As for #2, display in the Smart Weather app (note: limited space due to multi-device compatibility) — here is a proposal for comment:

In the blue dashboard view: present a descriptive value that maps to LUX ranges sim. to the chart posted by @GaryFunk, but perhaps with more levels between 10k and 100k daytime. Whereas if lux = 80,000 then display “Bright Sun”…or something like that.

In the list view: we can present both the descriptive value per above AND the actual LUX value on separate lines.


bonus question: for average home user, what is the ranked order or importance of these three assuming that LUX will be displayed as descriptive brightness value per above? : UV index, Brightness, Solar Radiation.


this side of the ocean during summer time the uv index is often mentioned (mostly to push people to protect them with hats, creams etc)

I know lux values as amateur photographer but honestly for weather … never seen that … ok I don’t look much telly :slight_smile:

Think Brian’s approach will be the only one understood by the average person, you have to link the data to something meaningful … just numbers ??.. better use the space for something else more ‘useful’ and propose this geek data in a separate corner. Guess those numbers wil hardly looked at on a mobile device :innocent:
my 2 cents (euro cents that is)


Ideally the different metrics could be moved around so the user can define what is important to them. One would figure in 2018 software would allow this sort of basic access and control? Regardless, if it came down to ranked importance it would be UV, Solar Radiation, Brightness.

On a related tangent will the new sensor be sensitive enough to detect and offer metrics for moon light? Or where there is lots of ambient street lighting besides the moon in the sky?


Part of the issue in trying to display descriptive terms is that a lot of factors would go into that. Just some simple things that have to taken into consideration is location, season, time of day, humdity and cloud cover. So bright sun may, just an example, only be 10k lux in the winter early in the morning where in the summer that same bright sun at that same sun angle may be 50k.

It is much more than just being able to say “If the lux is 50k it is full sun”.


At night it goes to 0 lux. It appears it can not detect lux values below zero.


What do people think about showing 0 ~ 100%? Also if that is includes a color strip going from light to dark? Using just these two would help human know the brightness, no?


I’ll just add to this, our eyes are a great filter for sunlight/brightness. While the “bright sun” lux numbers can have vast differences even during a single day, to our eyes, it is always full sunlight brightness with very little variance in perceived brightness. Much like a camera’s iris and shutter, our eyes adjust to allow just enough light to let us clearly see things but not do damage. If you our didn’t adjust we would either be blinded during the day or not be able to see at night.


I think percentage would be a much more understandable figure to understand. The problem I see is who is going to gather all of the factors that would determined what the maximum lux figure should be for every minute (or even second) of every day at every location on earth? For w/m2 there are formulas for that, is it for lux?


Just spit balling here but I would gather some defined intervals like the chart provided above would be a good starter. From there the developer could add what ever (middle) values they believe is useful to Human.


There are no lux values less than zero.

It looks like it does not use decimal values.


It’s basically rather simple

There are five scales and five main heat map colors. Each scale is divisible by 100.

Create an image that is 100 pixels tall and color it in based on the heat map color.

First convert the lux to foot candle and determine the level. The only issue there is which of two values to use to convert.


I should have said less than 1, not zero. But it does definitely use decimal points, as do all measurements.

Condition Illumination
Full Daylight 1,000 10,752
Overcast Day 100 1,075
Very Dark Day 10 107
Twilight 1 10.8
Deep Twilight 0.1 1.08
Full Moon 0.01 0.108
Quarter Moon 0.001 0.0108
Starlight 0.0001 0.0011


We are discussing the WeatherFlow sensor. IT doesn’t use decimal values.


I am not sure if I am average, but as a general user (not a weather geek), the only one of the 3 I would probably care about would be the UV factor. Living in Qld, Australia, we have the highest rate of skin cancer in the world, so that figure would be important to me. The kids are always asking if they have to use sunscreen when going for a swim. We use the general rule of always between 10 and 2, but outside of that, we wing it. I can see a situation where I have a rule with home automation where they will push a button (or ask Alexa), and depending on the UV factor, it will announce whether or not they need to use sunscreen or not. As a non-geek, I don’t know how I would/could use the brightness info??


Brightness in my home automation is to control roller blinds. Depending upon season say for winter if the light out put is low I will keep the blinds down to keep the heat in. If the light is high the system will leave the blinds up to allow the passive heating to keep the home warm and reduce energy consumption.

In the summer it will be the reverse to keep the house cool the shades will close and remain down to keep the UV / solar heat from entering the home, etc.

My primary focus is home automation, energy management, and reduced energy costs.


In your case you want to use Solar Radiation and UV.


At some point in the future, I want to get roller shutters for a particular room, and thought I would just use time as a trigger for them, but I see your use case.


I see value in having all three metrics as they each offer something to a person. One thing that had great value to me was those dual top down / bottom up blinds. Where you can open the top portion to what ever size for the best balance of light vs privacy but also leave the bottom portion closed for heat and privacy.

Only problem with those type of blinds is they can’t be automated . . .

So the inner window black out shades are the ones that roll up and down on command.