Incorrect resolution when booting my MacBook Pro

For some reason, my MacBook Pro now doesn't boot with the right resolution (1440 x 900). The System Preference panel about Screens and resolutions says that this resolution is being used at the moment, but I can clearly see that's not the case. Only when I plug in a 2nd screen (that one has 1680 x 1050), my MacBook Pro itself displays everything at the right resolution (i.e. 1440 x 900). When I unplug the 2nd screen this correct resolution remains intact (strange but true). My question is: how can I fix the problem that my MacBook Pro doesn't boot with the right resolution, because I don't always use a 2nd screen (which in this case seems to solve the problem).

In the meanwhile, I solved the problem. It turned out the contrast caused the trouble. I accidentally used a wrong keyboard shortcut in Photoshop and the one I used seems to adapt the contrast. I removed that contrast shortcut to prevent future mistakes.

I have the same issue

Hello, i hope you get this, ive done the exact same thing, thing is, i dont know which button or shortcut i hit in Photoshop, can you help me, which shortcut did you delete, and which one caused the problem? Thanks in advance.