Not directly, but Canon’s better ‘repairability’ will be something I consider. It won’t be among the first few things I think about, but if there were two close systems in my evaluation, I’d certainly lean toward the one with better service or that I had an ability to repair myself (i.e. parts access).

I realize I consider that way more than most people except for those running corporate photography companies (the ones that outfit dozens of photographers to do event and sports shoots, for example), so I’ll try to be very clear where that weighs in my decision process.

I’ve never been very impressed by anyone’s weather sealing. A rubber gasket at the lens mount, waterproof tape over the holes under the rubber, that’s about it. I can see that it would tend to keep water droplets from working their way inside the lens but I can’t imagine them surviving a steady rain – watersealed or not. I haven’t noted any difference in Canon, Nikon, or Olympus high end lenses.

Thanks for the fantastic blog.

The most common cause (it’s not shown in the teardown) is because the inner barrel travels along 3 metal ‘keys’ or rods and they’ve gotten loose. You can tell if that’s the problem by a simple test: the grinding is present when you zoom in and out, but if you turn the lens upside down and zoom in and out it’s gone or at least much reduced. That’s the key problem and can be fixed by realigning or replacing the keys. Often, though, the plastic barrel has gotten scratched or scored by that point and has to be replaced, too.

As with any zoom, it’s also possible for one of the collars in the lens to have broken or come off, but this is much less common and often causes a complete jam.

Roger