Originally posted by alexeyga
Actually it doesn't really matter if you're using the digital level... Have you tested if the sensor is actually true to camera's horizon? Just take a shot aligning one of the frame borders with something straight... then check on the computer if on the final image it's still aligned, because chances are - it's not...
i think the best way is to take a photo of something absolutely level and align it first on your viewfinder with the help of the AF points etc to check if you are holding the camera level, after that check in your viewfinder the horizon level reading if it is leveled according to that too, if not then it is off.
It would be ideal to be able to calibrate it yourself.