EF 100-400mm f/4.5-5.6L IS II USM + Extender EF 2X III = Lens Scratches?

[Far-Out-Dude]

I am looking at buying a Canon Extender EF 2x III to use with my R5 Mark 2 and Canon EF 100-400mm f/4.5-5.6L IS II USM Lens along with the Canon Control Ring Mount Adapter EF-EOS R that I already own. My concern is that I have heard that with some lenses the extender will come back and scratch the lens, I would like to know if this is a problem with this combination?

I would call Canon and ask myself but right now I am sick as a dog and every time I try to talk I start coughing for two o three minutes. Thank you much for your time.

[Far-Out-Dude]

It will not let me edit my other reply as I already had but I forgot to mention I tend to take very wide pictures when I take landscapes (Clearly this is not what that would be used for with this lens) but I like 16x20 and above. I want to get this one printed but everybody wants to guy it on me so I am waiting for a friend to return from FL and he does large scale printing from a professional printer.

[johnrmoyer]

I often use   EF100-400mm f/4.5-5.6L IS II USM +2x III with EOS R5 and it seems to me to work very well. The EF 2x III doubles the magnification while losing contrast and increasing small aperture diffraction blur. If the ISO is low enough, (difficult at F/11) then Canon DPP digital lens optimizer can remove some of the diffraction blur.

An example: https://www.rsok.com/~jrm/2024Sep30_birds_and_cats/2024sep22_hummingbird_IMG_1638c.html

Ruby-throated Hummingbird (Archilochus colubris) visiting Salvia greggii flowers in Norman, Oklahoma, United States on September 22, 2024 ; Canon EOS R5 ; EF100-400mm f/4.5-5.6L IS II USM +2x III ; 800.0 mm ; 1/500 second ; ISO 1600 ; F/11 ; distance about 4.5 meters ; backlit

The EF 1.4x III does less magnification than the 2x, but also often does not decrease contrast enough to notice and because of the larger aperture adds less small aperture diffraction blur. An example is at:   https://www.rsok.com/~jrm/2024Aug29_birds_and_cats/2024aug06_bluejay_IMG_1167c.html  Blue Jay (Cyanocitta cristata) on a cedar branch (Juniperus virginiana) in Norman, Oklahoma, United States on August 6, 2024 ; EOS R5 ; EF100-400mm f/4.5-5.6L IS II USM +1.4x III ; 560.0 mm ; 1/640 second ; handheld ; ISO 400 ; F/9 ; distance about 12.5 meters

An example using stacked extenders is at: https://www.rsok.com/~jrm/2021Sep08_birds_and_cats/2021sep02_bumblebee_IMG_3837c.html but it is difficult to make this work and at least one of the extenders must be 3rd party. The version III canon extenders are superior but cannot be stacked.

A Bumble Bee (Bombus pensylvanicus) was on a Zinnia in Norman, Oklahoma, United States on September 2, 2021. I made this photo with a very old lens as an experiment. I purchased the lens in 2011 and nearly wore it out. For this photo, it was attached to a newer camera body with an adapter with two telephoto extenders. ; EOS R5 ; Canon EF-S 55-250mm f/4-5.6 IS ; Kenko TELEPLUS HD C-AF 2X DGX ; Vivitar SERIES 1 1.4X AF ; F/16 ; 1/400 second ; handheld ; ISO 5000 ; 700mm

[Far-Out-Dude]

Thank you very much for the examples. I like contrast in pictures so the idea of losing a lot bothers me, I will have to stick with the 1.4 but I have decided to allow myself some more thought time. I would normally just order it but quite frankly I am not thinking right since I got sick and want my brain to clear up some more before I make any large purchases. I have not decided not to get one, though I now think when I do it will be the 1.4

I did order 3 more batteries, a battery case that will hold 4 batteries, a remote trigger so now I have one for each camera and some camera related tools to put in the bag as well as some cleaning supplies for the camera and lenses, that should keep the camera geek in me happy for about 15 minutes.