> > > At the bottom, higher N and C prices are probably because of the name > > because the build quality is lousy, although Canon puts internal motors in > > all of its lenses and Nikon is starting to. That adds value. > > <Real Question> > > Why? I would guess it adds weight. What else does an internal motor > offer? > > </Real Question>
Have you *seen* the USM motor on a Canon lens? (I have, courtesy of a fellow-shooter at a race who accidentally dropped a lens some 15' onto concrete). It probably weighs less than the drive shaft & gears in my Pentax AF lenses. The real reason, of course, is so the motor can be sized appropriately for the job at hand. When you use a Pentax AF camera the same motor has to be able to focus everything from the smallest, lightest lens to the heavyweight behemoths like the 600/f4 or 250-600/f5.6. That means you either carry around a heavy motor all the time or you end up with a camera that is slow to focus with the big glass.
