I have a Y460 - less than one week old - and am unable to properly control its screen brightness. I can set it, but then it will change on its own, going from 4/10 to 9/10 brightness without my touching anything.
The following factors could affect screen brightness and should be checked.
Windows power management/Lenovo energy management conflict.
Currently, I am using battery power. I am running the Lenovo management setting "Power Saver," which is also set in the Windows power area. In the Lenovo "details" area for the scheme, the settings are brightness = 4, dim = never, screen off = after 2 minutes (for both battery and a/c). In the Windows area, I have the same things set.
Still...the computer will go from brightness level 4 to up to 9. When I go into either power management to check it (or just use Fn + up/down), the brightness level will have reset to a standard of 9. This has happened in different programs or just on the desktop. It's worst when Firefox is maximized - that's when it tends to go up to 9 - but it's also happened to smaller extents in other programs (up to 6 when using MS OneNote, for example).
Similar things happened when I was running on A/C power and using a custom power scheme, but the above is the most controlled condition.
Display dimming going haywire
I thought this might be a problem with the computer dimming, then overcompensating when I touched the keys and it brightened again. So I turned off dimming in every single profile I use - the computer display is just set to turn off after a few minutes, with no intermediate dimming. This did not solve it.
Disabling the brightness smart control should allow the brightness settings defined in the power management scheme to remain in place as each scheme is selected unless overriden by the user.
energy managment > smart control.
The Y460 is equiped with a light sensor located between the slidenav and wifi led...