I have a late 2012 27” iMac but I find the display shows my Photos much darker and more contrasty than my MBP 15” retina. I have tried calibrating the iMac display by Apple's method and using a Spyder 3 colorimator but these actually make the problem worse. An Aperture modified photo looks that fine on the MBP looks darker on the iMac as much of the shadow detail is lost. I spoke with Apple Support but they had no suggestions.
I have tried to set the White point and gamma indentically to the MBP but no help.
Anyone tried to use an iMac for photo processing?
Oh man… this goes back a ways. 15 years, to be exact. Check out this old video of me on Apple stages in 2004 showing Motion at NAB and Apple Expo Paris!