My understanding based on this is that QTR expects 720. On Windows if it receives more or less than this then QTR itself resamples to 720. On OS X this resampling is done by the OS printing pipeline. My experience on Windows is that the resampling performed by QTR is fine, although you can get slightly better results by resizing in Qimage, but you have to examine the print under a loop to see it. My understand of OS X is that the resampling performed by the printing pipeline is best avoided.