Unexpected Discovery when mixing Tamron and Canon Lenses and Teleconverters.

[phkc070408]

I have a Canon 5D Mark iv and almost all of my lenses were Tamron’s.  I recently began to convert my lens collection to Canon.  I also had the Tamron 2X teleconverter and recently purchased the Canon 1.4x and 2x teleconverters.  I did some testing with the teleconverters and select ultra-Zoom lenses, and my results were highly unexpected.

I like to take pictures of planes, thus need the ability to zoom pretty far.  The primary lens I would use a tele-converter with is my Tamron 150-600mm.  I don’t see a point of putting a teleconverter on a lens that zooms less, when you have a lens that zooms to your desired focal length without a teleconverter.  I bought my Tamron 150-600mm and Tamron 2X teleconverter back during covid.  I was less than pleased with the teleconverter, since you can’t auto-zoom through the viewfinder, only through Live View.

Today, I tried something new.  I placed my Canon 1.4 Teleconverter in line with the Tamron 150-600mm lens, and it performed the same as with the Tamron 2X teleconverter, only autofocusing in Live View mode.  I then tried my 2X Canon teleconverter with the same lens, and to my surprise, it zoomed perfectly in both modes.

I then tried to reverse the test, using the Tamron Teleconverter with my two Ultra-Zoom Canon Lenses, the 70-200mm and the 100-400mm (I wish Canon made a 150-600mm zoom, but as far as I know, that is not an option).  When using the Canon 70-200mm lens autofocus worked with all three teleconverters worked in both viewfinder and live view mode.  Of course, it worked faster when in live view mode. 

When trying all three teleconverters with my Canon 100-400mm zoom lens, the Canon 1.4x Teleconverter worked in both modes (note that only the center focus point was available in Viewfinder mode, but that’s not an issue for me).  Using the Canon 2X teleconverter, AF only worked in Live View mode, however when using the Tamrom 2x teleconverter, AF did work in Viewfinder mode, using the center AF point only.  It also worked fully in live view mode.

To conclude, mixing competing companies’ lenses and teleconverters yielded more options in some cases than using the equipment of the same company.  The Canon 2X teleconverter permitted viewfinder AF with the Tamron 150-600mm lens, while Tamron’s own 2X teleconverter did not.  Likewise, the Tamron 2X teleconverter permitted viewfinder AF with the Canon 100-400mm lens, while Canon’s own 2X did not.

As I stated above, I don't see the point of placing a teleconverter on a lens when you have a lens that will reach your desired focal length without one.  That said, I will most likely carry the Tamron 150-600mm lens with the Canon 2x Teleconverter when I go plane spotting.

[johnrmoyer]

If a teleconverter does not report the F Number increase to the camera or of the teleconverter hides its presence from the camera, then the camera will attempt to autofocus when using the viewfinder even though the F Number is too large. Then autofocus usually only works in bright sunlight. The Canon teleconverter always reports its presence to the camera.

[Waddizzle]

Did you take the version of the teleconverter into consideration during your tests. 

[johnrmoyer]

Here is one of my experiments with stacked teleconverters: https://community.usa.canon.com/t5/Camera-Software/Using-DPP-and-stacked-telephoto-extenders/td-p/53... 

Northern Cardinal (Cardinalis cardinalis) in Norman, Oklahoma, United States on February 26, 2025 ; 1120 mm ; F/16 ; distance about 17 meters ; handheld using EOS R5 IBIS ; Canon DPP DLO and save 16 bit TIF ; gimp with GMIC plugin for additional noise reduction

Also on my web server at: https://www.rsok.com/~jrm/2025Feb28_birds_and_cats/2025feb26_cardinal_IMG_2841c.html 

[ebiggs1]

"... I don't see the point of placing a teleconverter on a lens when you have a lens that will reach your desired focal length without one."

It is all what you expect and are good with that counts. If you think the red cardinal is great than that is all that matters. Other opinions aren't important, however, I will offer to both of you that you may see the same or even better IQ if you shoot native FL and did the same crop ratio in Photoshop or DPP4. It is always a great debate which way is best. One thing for certain you won't suffer from the AF show down or f-stop penalty.

[ebiggs1]

Amazing you were able to get as good as you did with what you used.