iMAC 27" late 2009 During system start up the display initially shows a normal desktop and background image that has the correct value of gamma. As start up proceeds, after a brief normal display of about one second, this but the display changes to an image suggesting a high value of gamma is creating the image. This altered high gamma image, both in the background picture, and in all applications, persists. Consequently, buttons to be pressed do not appear as an area of activation surrounded by an appropriate graphic cannot be seen. Instead, to press a button, the user must move the pointer around to find the action area in the display. Similarly, scroll controls are not visible, and again the user must search by scanning the pointer around to find the scroll control area. Small low contrast characters may be invisible, very dimly visible, and often shown imperfectly. A factory sealed "NEW" graphics card was installed. There was not any change in the symptoms described above after the new GPU was successfully installed.
