For interviews we use the 50mm the most. The other two we use the most is 35mm and 85mm.
Dont forget with the letus you can plug in a 50mm and zoom into the ground glass and get a tighter 75-80mm look with the 50mm DOF. Same works with all the other lenses.
So most common we use is: 35mm, 50mm and 85 mm.
Emre Tufekci
http://www.productionpit.com