can focus.. you just won't be able to tell in the VF. do you use AF or MF? i haven't had much luck with AF and near MFD. can only use AF when it's not at MFD or even close. weird huh?
i'm going to use the EF-S focus screen now when i do stacking.. if not i really cannot tell the critical focus point at all. dang i need an external VF... haha