1.4 Extender

kvnkress

I've done some research here and on other sites and still not sure what to think. I want to get a 1.4 extender for my Canon 100-400 f4.5 IS lens (on a Canon 20D). Does anyone have any experience with this set up and, if so, what are your impressions and what are the drawbacks (other than losing an aperture stop)? I've heard you loose AF but I've also heard you don't. What about IS?

Primary purpose is for surf pictures, but also nature shots.

Thanks in advance.

-Kevin

kdog

Unless you plan on manual-focusing, it's a waste of time, IMHO. You will absolutely lose autofocus unless you tape pins. In that case, the lens will hunt, but usually will eventually lock-on. By that time you've probably missed your bird or surfer. I also can't imagine the machine-gun kind of thrashing that the AF does while it's hunting is very good for lens. That combined with a modest loss of image quality makes it a losing proposition in my book. Your mileage may vary.

BTW, I've used three different extenders, two bodies, and two different lenses (100-400 and 400 F5.6) trying to make this work. So, I think that qualifies me to be very skeptical of people who claim to have great success with that combination.

ziggy53

kvnkress wrote:

I've done some research here and on other sites and still not sure what to think. I want to get a 1.4 extender for my Canon 100-400 f4.5 IS lens (on a Canon 20D). Does anyone have any experience with this set up and, if so, what are your impressions and what are the drawbacks (other than losing an aperture stop)? I've heard you loose AF but I've also heard you don't. What about IS?

Primary purpose is for surf pictures, but also nature shots.

Thanks in advance.

-Kevin

The Canon 20D will not AF with lenses of less than f5.6 aperture. Adding a 1.4x teleconverter will reduce lens efficiency by 1 stop, so at the long end of an EF 100-400mm, f4.5-f5.6 L IS USM you will lose AF. AF speed and accuracy will also be affected on the short end of the zoom.

It is possible to tape the contacts of the teleconverter which should allow AF to continue, but AF speed and accuracy will be affected. You may also manually focus with focus confirmation from the camera.

Some third party teleconverters do not pass the aperture information and they may be used without taping. Image quality is more in question with the third party converters, but some people get good results.

I've used a manual focus lens with an adapter that allows focus confirmation to track a jet ski, so I suspect manual focus with confirmation is possible for both surfing and nature. Running wildlife and birds would probably not be practical.

IS will still be a benefit but the extra magnification means that the IS will be less effective than without the converter. A tripod will beat IS any day for basic stabilization.

kvnkress

Thanks for the info. I appreciate it!

Bear Dale

I like using my 1.4x and 2x teleconverters with my 100-400mm

pathfinder

As a general rule, TCs work much better with really good prime lenses, than complicated multi element zooms.