Extender EF 2x III compatible with EF 100-300 f/5.6L on EOS R?

[rickmp001]

Hello,
Is the Canon Extender EF 2X III  compatible at all with the EF 100-300 F5.6L on a Canon EOS R body with Mount Adapter EF EOS-R? This is not on the compatibility list, but I was wondering if this combination would work, even if only in manual focus mode. Have been a Canon shooter since 1975 with an F-1 body (non-N variant). Thank you...

[shadowsports]

My apologies somehow I didn't make it clear.  Without an extension tube, the TC will contact the rear element of the 100 300. You are risking damage.  Remember the lens is not on the compatibility list either.  What you are proposing...  a mirrorless body with an adapter, a TC, an extension tube and the lens.  From a practicality standpoint, think about what that's going to look like, then more importantly how reliable it might -not- be.

Even used, a EF 2.0x TC III represents a considerable investment for somebody who professes to be "budget conscious".  I believe putting that money towards a new lens would be a wiser choice in the long run.  But...  Just because I wouldn't do it doesn't mean you can't try.  We all have our standards.  So wishing you luck with this endeavor.

[ebiggs1]

If the Canon tel con doesn’t work you can try the Kenko . I have not tried it since I don’t do extenders but I understand it fits most everything.

[johnrmoyer]

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@ebiggs1 wrote:

If the Canon tel con doesn’t work you can try the Kenko . I have not tried it since I don’t do extenders but I understand it fits most everything.

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I have used the Kenko and it works well. It does not work with every EF and EF-S lenses, but works with more than are mentioned on the Kenko product support page. It gets better results when used with a better lens. I used it as a less expensive extender than the one from Canon that would work with a less expensive lens than the one from Canon.

The upside is 2x magnification without changing minimum or maximum focus distance.

The downsides are lens flaws are magnified, some additional vignetting, DSLR will autofocus in live view only, small aperture results in diffraction blur, and possibly a little less contrast.

https://www.rsok.com/~jrm/2017Feb07_birds_and_cats/2017feb01_cardinal_IMG_0929.html 

The reason that the focal length is listed as 600mm for a 300mm lens is that a Kenko Teleplus HD C-AF 2X DGX teleconverter was attached. This was taken hand held while sitting on a chair on my front porch. The gimp gmic plugin Richardson-Lucy deconvolution was used to remove small aperture diffraction blur. F/11 is wide open for this combination of lens and teleconverter. Focus was manual. After cropping and resizing to 40%, an unsharp mask was applied.

Camera Model Name	Canon EOS 80D
F Number	11.0
ISO	640
Shutter Speed Value	1/512
Focal Length	600.0 mm
Camera Temperature	25 C
Focus Distance Upper	12.61 m
Focus Distance Lower	9.36 m
Lens ID	Canon EF70-300mm f/4-5.6 IS II USM
Field Of View	2.2 deg
Hyperfocal Distance	1692.99 m