Can't work quickly with a mamiya 7? Help with rf?

[GarageBoy]

So I tried shooting with the mamiya 7 at a parade and man, I have such difficulty using the RF. Can't tell if my horizon is straight, can't focus and recompose quickly due to frame lines... any tips?

 

[mfogiel]

Practice makes perfect. Imagine Erich Salomon with his Ermanox
http://gmpphoto.blogspot.com/2015/03/erich-salomon-first-modern.html