Glad you asked, because
Lumos is indeed special, and you should definitely give it another try. Run it for at least 48 hours, and make sure you take the calibration wizard seriously (more on that in a minute).
First of all, it's important to put this into the right context --
the backlight is the number one drain on our battery that we have control over. With your backlight set to maximum, the screen looks fantastic, but you can almost hear the slurping sound of your battery being sucked away.
Even while charging, if your backlight is set to 100% you will heat up more, and charge more slowly because of the massive additional current drain. If you could operate at 30% or 40% all day long, you could get up to double the battery life -- but
running at 30% or 40% all day is unrealistic for most of us. We go outside, and still have to see the screen. Perhaps we run a GPS application in the car that we always want at maximum brightness.
Whatever the reason, we usually don't optimize our day-to-day, moment-to-moment backlight usage, and if we could, it would save us a ton of battery power. Lumos does that for you -- the built in backlight management will not.
So, what about that calibration wizard? Well, it basically helps you determine what
realistic values (this is important) should be set for the boundaries of your backlight in your personal situation by measuring incoming light in your various personal environments. This allows it to determine a curve that gets applied based on current lighting conditions -- and it works. For example:
I work at my desk in a relatively dark room. After calibration it was determined that I can read my phone clearly in this light at only 30% backlight and this ended up being the minimum set by Lumos. Calibration also had me go stand in the Colorado sun outside my house and determined that I could read the screen ok at 80% even in direct light, so that became the maximum. You could determine this manually, and then set it manually, but the wizard is a very nice tool for helping make sense of what you can actually work with.
Once Lumos is calibrated it starts to work it's magic. At my desk, as calibrated, I can see the backlight set to 30% and the power usage is minimal. Outside in the sun I can see it set to 80% and the power usage, while much greater, is still significantly less than if I had left it at 100. The real neat thing is, I can also find it sometimes at 40%, or 50%, or 60% because it uses the minimum and maximum detected light calibration values to create a curve for applying the backlight settings. This way, I can always see my screen whatever the lighting around me, and I get the benefit of having my backlight turned down as low as I am comfortable with it as much as is possible without my intervention. That saves a lot of power, and takes zero effort. Who wouldn't want that?
The 'smoothness' is mostly a matter of polling and change time, which defaults to 1250/2500ms to save more battery life, but can be set to whatever value you choose for faster/smooth backlight adjustments. In fact, all the settings that are determined by the wizard can also be set manually, and exceptions can be set for programs like Garmin (gps) to make sure they always get maximum brightness.
I really do hope that more people, especially people with battery issues, will more strongly consider the backlight as a primary cause of power drain, and consider trying
Lumos along with your other battery tweaks for at least a few days. I think it just might surprise you.
EDIT: Screenshots
