Maybe it's my age, or maybe it's my inability to find very very concrete, straight-forward info regarding Nikon DSLR compatible lenses, but if someone's selling lens described as: 1) An Auto (Auto = Autofocus? Doubt it....) Telephoto Lens Vivitar 135 mm f/2.8, Meter coupled (does that mean I can meter on a D50?), and made to fit a Nikon (what mount?). 2) 70-150 f/3.8 MC, Close Focusing (quasi-macro, right?), Auto Zoom lens for Nikkor/Nikkormat N/F, Nikon F and EL lens series (are these mounts?), Meter Coupled and Auto Diaphragm Control. 3) Vivitar 135 mm f/3.5 Auto Telephoto lens, Nikon F Nikkormat mount Will they meter and focus properly on my Nikon D50? What about the 2nd description? It says "MC" (don't know what that means), but fits a Nikon F mount camera, so I'm most confident about this lens. I'm guessing they're all manual focus with no metering, but one can hope. Thanks in advance.