Lack of contrast with new screen and digitizer

After replacing the screen and digitizer on my 4S I find that to obtain the correct contrast on the screen I must hold the iPhone at a slight off-axis angle (approximately 30-40 degrees), I have tried all the controls associated with the iphone. The display, looking straight on, looks milky. It almost appears that the brightness is too high but adjusting the brightness does not improve the lack of contrast.

Any suggestions greatly appreciated. Maybe the new display is faulty!