By the way H you wont need a B/Mask on the Tak,
it just snaps into focus.
I am 60 and I have never used any computer, and/or any focusing device to get focus, and I am half blind, LOL, and some of my pics are pretty reasonable
Just move it into and past focus, you will see the B/Mask effect instantly, in the scope.
I bought one once and sold it the next day totally useless on a Tak mate.
But that is only MHO
Leon