Backlight power consumption analysis.

[Colin Ian King]

Hi there,

More power consumption analysis... this time I investigated the current 
drawn when cycling through all the back-light levels on various 
machines.   The results are interesting as they show non-linearity in 
power consumption.  A brief summary of my findings is:

All machines showed up non-linear current increase as backlight levels 
increasse.
At the highest backlight setting the machines show a reduction of battery
life from ~12-22%.  The Lenovo ThinkPad X220i shows a remarkable increase in
power consumption as we approach the highest brightness levels, and so does
the HPMini-100 to a lesser degree.

The general rule of thumb therefore is try not to exceed more than 2/3 the
way up the brightness scale.  The top 1/3 of the brightness scale impacts
of power consumption disproportionately.

If you want to see the data and some interesting graphs, I've put a 
LibreOffice spreadsheet in
with a brief write-up of the results in:

http://zinc.canonical.com/~cking/power-benchmarking/backlight-non-linearity/

Colin