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.

[deebatman316]

The EF 100-400mm is compatible with extenders. If a lens is incompatible it won’t mount on the lens at all. Canon’s teleconverters physically extend into the lens. Also I wouldn’t recommend using a 2x teleconverter. At most I would use a 1.4x teleconverter. Even then you loose a stop of light or 2 with the 2x teleconverter. Also the teleconverter can impact AF performance. 

[Far-Out-Dude]

First thank you for the reply. My brain is still not working the best after so many days of fevers so forgive me for what may sound like stupid follow up questions. I am sure the lens is compatible, but is there a chance for the lens to get scratched? What would the  I am having a hard time thinking of how to word this, I am sorry, the increase in magnification be on the 1.4? If I figure it right and knowing me I am not at 400mm it would only increase it to 560mm? That does not seem worth the money when the 2.0 would make it 800mm at the same 400mm? It is numbers so I am sure I am not understanding something, I am horrible with numbers. Also what would be the difference in F stop loss between the two extenders? Thank you again.

[deebatman316 · Accepted solution]

You cannot stack the version III teleconverters. With the 1.4x teleconverter you loose one stop of light. With the 2x you loose 2 stops of light. Your lens can’t get scratched there’s rubber on the end of it. With the 1.4x teleconverter your focal length at 100mm would be 140mm. Then at 400mm it would be 700mm. With the 2x teleconverter your focal length at 100mm would be 200mm. Then at 400mm it would be 800mm.

[Far-Out-Dude]

Thank you for the corrections on the math, like I said, I am horrible with numbers. Now what do you mean by they can't be stacked? If I am thinking the same kind of stacking I thought that was done in a program like Lr or photoshop? I am still learning so I appreciate the explanations. I have to get stuff ordered no later than tomorrow as the company closes between the 11th-20th for Passover and I would like to get the items to learn them before turkey season starts on May 1 Thanks again.

[deebatman316]

When I mean stack teleconverters I mean connect multiple of the together. This IS NOT POSSIBLE with the mark iii teleconverters. The 2x teleconverter + 100-400mm equates to the RF 200-800mm F/6.3-9 IS USM lens.

[Far-Out-Dude]

Oh okay, that never even crossed my mind, is it something that could be done with older models? I am not interested in the older models, it's just an interesting point of conversation. Thank you again for all the help. I'm going to be a little bit before I can reply again on being in a good super tired again from being sick I got to close my eyes awhile but I will reply later. Thank you again.

[deebatman316]

Older teleconverters can be stacked. But limitations do exist like slower AF performance or reduced optical IS.

[jrhoffman75]

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@Far-Out-Dude wrote:

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.

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Depending on the final use of your images, before you invest in the extenders, try just cropping your images. The R5M2 has plenty of pixels.

Most users will tell you the image quality of the 2X extender is not great. Plus you lose two stops of light and a slowdown of auto focus. The 1.4X isn't as bad, but there is still a hit.

The most I do with my images is a 13x19 print or digital display for my camera club or sharing. I have run informal tests with my 1D X Mark III (~20MP) and see no difference in image quality between cropping in or using the 1.4X extender. I have the EF 100-400mm f/4.5-5.6L IS II lens and definitely see an AF slowdown with the extender. 

[Far-Out-Dude]

I have been offered money for my prints by those that have seen them, to me I have always felt they needed to be closer to bring in more detail. At the time all I had was a Canon M50 Mark I and a Canon EF 70-300mm f/4-5.6 IS II USM Lens and I have always been told to upgrade your lens first, so I got the Canon EF 100-400mm f/4.5-5.6L IS II USM Lens and I feel there was a big difference, even friends that saw my pictures commented on how much better the pictures I took looked. I knew my next upgrade was going to be a camera but put that off for both money and because my girlfriend became ill after a brain aneurysm bleed and I took care of her for 379 days until she died and I have been trying to get back out to take pictures but between depression and problems with my eye making it hard to read the manual and see the controls on the camera and problems with my foot because I had foot surgery 3 days before her brain aneurysm bleed and ruined it because I was on it constantly (Not blaming her, just telling what happened, I wold do it all over again and have the same result if I could have more time with her again) I have not been out much at all. My favorite subject are wild turkey and turkey season starts on May 1  so I would like a little time to learn anything I may buy. I had wanted to trade in the 100-400 Lens to a Canon RF 100-500mm f/4.5-7.1 L IS USM Lens but was only offered $850.00 USD for a lens I have only had for two years come April seventeenth and other than May of that year I bought it (2023) it has been a truck rider that has barely been taken out if the bag the entire time because of the reasons explained above, I can't justify that kind of loss ($1,752.91) for a product that is almost brand new. I enjoy shooting wildlife and have been playing around with birds in flight.