Loss of sharpness on Canon 100-400

Cporosus1 wrote:

Hello everyone,

I have a question to ask- is it possible for a lens (in my case, the Canon 100-400) to lose sharpness? I have been using this lens since 2008 (it is the "dust pump" model not the newer one) and I have traveled all over the world with it (Australia, Belize, Brazil, Costa Rica, Indonesia, Singapore, South Africa, Sri Lanka, etc. some multiple times). Despite a few superficial blemishes from years of wear, there does not appear to be anything mechanically wrong with it. However, over the last couple of years, I've noticed it just doesnt "nail" some of the shots that it would have before. It seems I need to be almost entirely still to get a sharp wildlife shot, whereas before I could be moving or on a boat, etc. and still get the shot. Should I give up and get a new lens or do you think a cleaning may help? Can accumulation of dust inside the lens cause this? I don't think it is the camera itself. I have a Canon 7D Mark II and I purchased it much more recently (November 2016) and my smaller lens doesn't have the same problem.

Thanks!

Maybe the IS switch is dirty, or the IS module is dead.

If IS is working, you will see the view get more stable after you half-press the shutter button, and become less stable a couple of seconds after you release the shutter button.  You should also feel a small kick when it kicks in and out.

If the switch is on, and there is no IS, try moving the switch through its range several times to wear away any oxidation.