Understanding light levels

[Alex Stanciu]

Hello.

I'm struggling with some autobrightness profiles and I'm stuck at understanding how light levels are interpreted...

Example: on my Desire S the light sensor gets the following readings of the ambient light levels (in lux): 160, 225, 320, 640, 1280, .. 10240. So min is 160, max is 10240 -> I already calibrated Tasker

Prior to calibration I had some profiles to help me see which ambient light level triggers which light level in Tasker, but after calibration :
- an ambient light level of 160 lux triggers the 0-1% light level (OK)
- an ambient light level of 225 lux triggers the 6-13% light level (KO)
- an ambient light level of 320 lux triggers the 14-25% light level (KO)
... etc

If 160 is minimum and 10240 is maximum, how can 320 be somewhere between 14 and 25%?...

[Oon-Ee Ng]

Why not just use %LIGHT?

More to the point - I think its not scaled linearly, because lux
doesn't actually scale with our visual sense of brightness.

[RudeboyX]

He is using %LIGHT.

Heres a quick breakdown of lux levels

Illuminance	Surfaces illuminated by:
10−4 lux	Total starlight, overcast sky[3]
0.002 lux	Moonless clear night sky with airglow[3]
0.01 lux	Quarter moon
0.27 lux	Full moon on a clear night[3][4]
1 lux	Full moon overhead at tropical latitudes[5]
3.4 lux	Dark limit of civil twilight under a clear sky[6]
50 lux	Family living room lights (Australia, 1998)[7]
80 lux	Office building lights in hallway/toilet[8][9]
100 lux	Very dark overcast day[3]
320–500 lux	Office lighting[10][11][12]
400 lux	Sunrise or sunset on a clear day.
1,000 lux	Overcast day;[3] typical TV studio lighting
10,000–25,000 lux	Full daylight (not direct sun)[3]
32,000–130,000 lux	Direct sunlight

[RudeboyX]

you can also view the graphs on the below webpage to get a visualisation of the steps.

http://msdn.microsoft.com/en-us/library/windows/desktop/dd319008%28v=vs.85%29.aspx

Regards
RBX

[Nplus1]

Thank you for the graph RudeboyX.

I was expecting Tasker to plot the values similarly to what we have in the first graph (5 out of 10 steps with low lux increase), but apparently we're closer to the second graph, almost linear.
I suppose I can easily take the values from your link, add them to Tasker (keeping in mind my max value is 10240) and I'll be fine.

[RudeboyX]

Glad to be of help.

RBX