EOS R compatibility with EF lens and 2.0 extender...

[kaiju8]

Hey guys, im trying to get as much mm out of my lenses and wandering if my canon r with ef to rf adapter will take my 100-400 EF lens with the 2 0 teleextender. Will that work? Ive heard ( long time ago) that the 100-400 will not work with extender because the back of the lens sticks out too far?

Is this true?

If it does work ( which i dont expect) it will make my 100-400 an 800mm birdwatchingmonster...

Thanks for any input!

[deebatman316]

EF Teleconverters are compatible with the EF-RF Mount adapter. As long as the lens being used is the Canon brand 100-400mm. Who knows what the compatibility of 3rd Party gear is. Also AF will be slower and the aperture goes down by 2 stops with the 2x teleconverter.

[Waddizzle]

Will it work?  Probably.  How well it will work will depend on the camera model.  I would expect mediocre performance with the flagship model R1.  Performance goes downhill from there using lower priced models.

 The basic problem will be the reduced amount of light reaching the AF sensor, especially at the 400mm setting.  Because of the light reduction, you’ll wind doubling your ISO , halving your shutter speed, or some combination of those two.

[shadowsports]

Kaiju8,

Save your money and buy it appropriate lens for your camera.  Please listen to my colleagues. Trying to go the teleconverter route is not going to end in success or your satisfaction.  

[jrhoffman75]

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@kaiju8 wrote:

Hey guys, im trying to get as much mm out of my lenses and wandering if my canon r with ef to rf adapter will take my 100-400 EF lens with the 2 0 teleextender. Will that work? Ive heard ( long time ago) that the 100-400 will not work with extender because the back of the lens sticks out too far?

Is this true?

If it does work ( which i dont expect) it will make my 100-400 an 800mm birdwatchingmonster...

Thanks for any input!

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I ran some informal tests with that lens back when I had my 1D X Mark III. I compared images with the 2X with images without but cropped to the same size. Cropped images looked just as good but I didn't lose the light and AF speed was better. 

[ebiggs1]

"Save your money and buy it appropriate lens for your camera."

Agree. Using the 2x is an all around bad idea.