I own a Macbook pro (15'4) with Yosemite.
I used to use it without an external display. The brightness was very powerful :)
I've just plugged a thunderbolt display (Mac 27''), and then removed it. I even restarted my MacBook pro right after.
Now, I found that the brightness is not as powerful as before, even on MAX :(
My color profile is the one by default (LCD color).
Is there an explanation? Have someone ever experienced this?