First off, I'm not a pro at Maya. I can manage to create simple animations with keyframes. That being said, I recently discovered how to use Mental Ray and Physical Sun and Sky when rendering out my images. I just clicked the 'create'-button by Physical Sun and Sky and left it at that. At first when I rendered out images it looked a little bright but it was fine.

Later when rendering again the image became too bright.

And I have no idea why. When using cameras the image became too dark. That was usually fixed by deleting the Physical Sun and Sky and creating it again. Otherwise I had to open up a earlier version of the scene.

I would appreciate if anyone could tell me how to fix this.