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

When I had this lens I was never able to get images I thought were of acceptable IQ with the 1.4x attached. On the other hand you will probably have folks chime in that have.

You can Bill, but you don't have AF anymore, just manual. I think most people would give it a thumbs down.

I used mine for a while on a Pro body which gave me autofocus to f/8 but it was slow and the I.Q was not acceptable and I sold the lens which I never really liked anyway.

Mind you I know others that swear by the 100-400.

IME the 100-400 is very sensitive to filters so first off, get rid of it if you have one attached. At 400mm with the 1.4 tc attached you are at f8 so there's not much scope for shutting the lens down a bit to squeeze more IQ, but if you went 1/3-2/3 stop down from f8 your IQ would improve. I would think that at that point you will be as much prone to the effects of camera shake as you will be of any loss in IQ from the 1.4 tc attached. Nothing like trying it out with a friend's tc or at a store with a good tripod.

Thanks for the info. I'm not going to try it. The lack of AF is a killer for me.

Bill

Quote:

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Originally Posted by BillTyler

The lack of AF is a killer for me.

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You can do the old tape the pins hack if you want AF. But in the end it's hard enough to get stellar shots so why make it any harder.

http://www.michaelfurtman.com/taping_the_pins.htm

Hi Bill

The best advise is to test for yourself. Would borrow a 1.4X and try it ... for static subjects. Need a good test target and firmly secured to a good tripod. I don't use the combo much at all but did the test and was pleasantly surprised !!!

btw if you decide to test do so wide open and use different focal length !!

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.

Thanks to everyone for all the information.

Bill