David Nelson mused: > > >>Am I right that manual focus and auto focus differ only in the way the > >>lens focusing ring is rotated? I think I am right :). > > > > No, all Pentax lenses focus rings rotate the same direction > > Rob, I read the comment the same way you did, initially, but then > realised that it wasn't the direction of focus ring movement but the way > that focus ring movement is effected (mechanical drive versus hand on > lens) that Boris was talking about. Ah, the joys of the engrish language. > Personally, I don't find that the focus confirmation is always accurate > enough for my tastes, though I'll agree that it's often hard to focus on > the screen on something at the edge of frame. But you're right, it's a > mystery why they couldn't make focus confirmation work for all the AF > points. Strangely enough, only centre focus works with the 1.7x AF > converter.
I assume it's just laziness (or, to be charitable, software economy); with an mf lens you don't have the digital signal pin, so you don't know the maximum aperture of the lens unless you're reading the A contacts on the lens mount. I'd guess that with a small-aperture lens some of the outermost af points might not work correctly. [mind you, most of the earlier lenses have a wider maximum aperture than those f4.5/5.6 AF zooms, so perhaps I'm just being too kind]
