Viewfinders are also usually designed to have around 1x magnification with a 50 mm lens. That's why the viewfinders on crop DSLRs seem smaller than on a fullfra

Viewfinders are also usually designed to have around 1x magnification with a 50 mm lens. That's why the viewfinders on crop DSLRs seem smaller than on a fullframe, because they literally are 2/3rds the size.