Hasselblad H cameras. How does the viewfinder image correspondent with the photograph?

The Hasselblad H cameras are modular. There are different digital backs for each camera available which actually feature different sensor sizes.

How does the image in the viewfinder correspondent to the image that the sensor will take? With different sensor sizes the image wont be the same.

My Nikon fullframe DSLR masks the viewfinder when it is set to APS-C mode so I know what the image will look like. How does a Hasselblad H cameras viewfinder show me what image Im about to take?