I have an unchipped adaptor (the Cameraquest one). I use the 85P on my 5D, and also used it on the 5 when I first got the adaptor. I have no real problems focusing it with reasonably static subjects with either the original 5D screen or the gridded one, but it's not always so easy with moving subjects. However, this lens is the Zeiss one that I use most frequently on the 5D - although at the moment, it's back on my 137MA for old times' sake.