First the diamond engagement ring is weighed in a vacuum. Next the colour is determined. The clarity is then estimated only after the diamond has been magnified by 10 times.
Factors in choosing ideal cut diamonds are broken down into four groups, know as the Four Cs. They determine the quality and worth of diamond.
While the weight of princess cut diamond is important, it doesnt necessarily provide the "perceived size" of diamond. A shallow cut diamond will have a greater diameter, and will therefore look larger.