Nikon D810: What You Need to Know
Electronic 1st-curtain Shutter and Redesigned Mirror
Some people will never even notice this improvement, but for certain photographers the new electronic first-curtain shutter and redesigned mirror assembly in the D810 is a very big deal. Like all ultra high-resolution cameras the D800 and D800E were very demanding, especially when used in the studio. We had a lot of headaches trying to get optimal resolution out of the D800E at certain shutter speeds where the movement of the shutter and mirror could actually introduce blur into images. We had similar issues with Sony's 36MP A7R.
With the D810, Nikon has introduced an electronic first-curtain shutter option, which reduces the amount of movement and shock generated by the simple action of taking a picture. The mirror balancer has also been redesigned with the same aim and according to Nikon these changes have 'nearly eliminated' internal vibrations. This is great news for landscape, studio and macro photographers.