Why would I add the D810 weight? To start with, I only carry one body when travelling. Secondly, other than sensor size, the D810 and A7R are hardly comparable. The D810 is vastly superior when it comes to AF, frame rate, buffer size, image quality at high ISO, image quality at low ISO, build quality, battery life, ergonomics etc. It's a totally different kind of machine. But since you ask, the D810 is 140g heavier than the D750. Also, when travelling, I carry two batteries and change battery once per week, more or less.