Powiedzial bym ze nawet wiecej jak wspomagacz...
Wyostrzyc MF precyzyjnie na gladkiej matowce (zwlaszcza w dslr'ach) to raczej totolotek i spora sztuka.

Zreszta ta opinia swiadczy o tym ze to nie lekarstwo a dodatek dla "old stalka fans":
I've never actually read of *anybody* who has fitted these focus screens that have said "it proves that my camera is back/front focusing"...everyone always reports that is concurs with their camera's AF system!!!!