I found I need to use Aspect Fit but can't find it anywhere in the IB. Supposedly should be under the Attributes Inspector "Mode" but this doesn't exist. I set the constraints to "Superview" which is a Box an had to set scaling to none otherwise it doesn't fill, programatrically at runtime the image will change and no constant size but doing this resizes the window's width to the new image width. The images are portrait and want to fit into landscape which is why I chose Aspect Fit no Fill.
Has it been depricated or am I missing something ?