Extenders

I have a Canon 77D and use if for bird photography with a Sigma 150-600. Any recommendations for an extender that will work and keep the lens' autofocus feature.

"None!"

Right now you should already have more sensor pixels than lens resolution. Why add a fishy optical device that cramps 16 instead of currently 4 pixels into one dot of lens resolution? Crop as needed or get closer; thats all you can do.

If you want to play with one don't go more than a x1.4 tc and use the latest Sigma teleconverter that will work best with the Sigma 150-600. Stay away from the old out of production TCs as they don't play well with the newer Sigma lenses. Just my opinion.

I have a Canon 77D and use if for bird photography with a Sigma 150-600. Any recommendations for an extender that will work and keep the lens' autofocus feature.

 

There are two problems with TC and autofocus.

 

One is that with the smaller effective aperture, it is harder for the AF to get the signal that it needs.

 

The other is that the focus, as seen by the AF sensor, changes faster by the TC factor.

 

I have a Nikon mount TC that allows for the mechanical (in camera motor) AF system that

Nikon had early. There is gearing in the 2x TC that slows down the focus mechanism by

a factor of 2. But Canon doesn't have this system.

 

With motor in the lens AF, though, there is no slowing. The result is that, at least for

the one I have, is that it overshoots, tries to go back, and eventually gives up close

but not quite close enough.

 

As well as I know, 1.4x converters often enough work, as the factor isn't so big,

and the system can handle it. Often enough.

 

Sensor signal depends on contrast in the scene, but the lens can't control.

 

I don't know of any lens that allows for slowing down the motor.

This used to be the way to go, but I've never tried it for reasons suggested above:

Taping The Pins on 1.4x tele-extender to restore autofocus in Canon cameras

Taping the pins prevents the extender from being detected, so if you're in a situation in which the lens + TC is too slow for your camera's autofocus system (for many EOS cameras, that means slower than f/5.6), autofocus will still try to work. But it doesn't change the physical limitations of the autofocus system. Bottom line: depending on the lens (and focus length for some zooms) and body, autofocus may work well, poorly, or not at all.

I seen it done with this lens and a similar EOS body.

 

I concur with Mark and Steve:

 

> the best tele-converter / extender "to try" is the newest Sigma x1.4

> the auto focus will not work properly, though it may attempt to work and those attempts will likely garner mixed results. This behaviour is a limitation of physics, whether you tape the pins or not. However taping the pins seems in most circumstances to make the AF want to work more often - that's sometimes bad, because it may just hunt.

> these are the pins to tape if you want to give it a try:

 

WW

 

Addendum: my opinion, other than as an exercise to see what happens, I would never use that set up for Photography - either get closer or crop a little bit, or both.

Edited November 20, 2019 by William Michael

You may find this thread from a while back interesting. In a reply I posted examples of testing a combo of a 6D and Tamron 70-200mm and a Sigma 1.4x TC and later in the thread some testing examples with the Sigma 2x TC with nice results for what it was. LINK Edited November 22, 2019 by Mark Keefer