A:Answer Mirrorless camera weigh less than regular DSLRs because they don't have the mirror system that is needed for the optical viewfinder. What you need is to read how a mirrorless camera uses the viewfinder to show you what you're looking at-it's the same as the back screen, but with the Nikon you can see what you are adjusting when you change ISO, aperture, and/or exposure. A new user would find the weight difference the biggest difference if they've used a DSLR.