Is the Canon 100-400 usable with 1.4x?
I have the Canon EF 100-400mm f4.5-5.6L IS USM, and considering budget am interested in using it with a 1.4 extender on a 50D body. Can anyone tell me if this is going to give acceptable results? I know the math of f/stop loss, but I don't know how sharp this combination will be.
Thanks,
Bill
Results not good with 100-400 and 1.4x combo
I tried this combo with Mk2N recently in Alaska and was disappointed with the results. While I love the 100-400 by itself, I would not recommend using it with an extender.
As has been pointed out already, you lose autofocus unless you are using a 1-series body, but even with that, I found the focus to be pretty soft on every shot. It just didn't work well, and I'm not just talking about a few shots. When I tried it, I was sitting in the woods about 15 feet from a goshawk with a kill. I added the extender to try and get some really close head shots. I shot some with and some without flash, due to being in a dimly lit area under a canopy of trees. When downsized, some of the photos were acceptable, but at full size I did not find anything really tack sharp from over 100 shots.
I can attest to the fact that my 100-400 is outstanding by itself. It's my favorite lens for flight shots, and I get tack sharp results consistently when I use it without an extender. I have also verified that the focus calibration on the camera body is spot on. So my conclusion is that the 100-400 does not work well with and extender.
By contrast, I can throw either a 1.4x or 2x extender on my 300 f2.8, and get much better results.
I hope this helps.