Canon Extenders: I’ve recently came across an article in which it states that two Canon extenders, the 1.4x III and the 2.0x III, can be stacked, with the use of a 12mm extension tube...

rwags18 Loc: Oregon

I’ve recently came across an article in which it states that two Canon extenders, the 1.4x III and the 2.0x III, can be stacked, with the use of a 12mm extension tube, and not lose the auto-focus feature. It states that if you use a piece of insulated tape and place it over the contacts of the 2.0x extender, that will eliminate the loss of auto-focus with the 2.0x extender. Has anyone ever done this? What is your opinion of how this would affect the picture, if any?

robertjerl Loc: Corona, California

rwags18 wrote:

I’ve recently came across an article in which it states that two Canon extenders, the 1.4x III and the 2.0x III, can be stacked, with the use of a 12mm extension tube, and not lose the auto-focus feature. It states that if you use a piece of insulated tape and place it over the contacts of the 2.0x extender, that will eliminate the loss of auto-focus with the 2.0x extender. Has anyone ever done this? What is your opinion of how this would affect the picture, if any?

IQ goes down among other things.

Years ago a photographer for one of the now gone magazines got weird and put multiple extenders and extension tubes together with a lens so the result looked to be 3-4 feet long and the focal length went over 2000 mm. It took two tripods, one for the body and one for the lens to prevent bending and breaking. Then he took shots of a small hawk at some ridiculous distance. The results were barely OK, but if for say bird ID and not framing a picture it was just fine. And of course, no auto focus.

rwags18 Loc: Oregon

robertjerl wrote:

IQ goes down among other things. br br Years ago ... (show quote)

Interesting. My thought is that the image quality would severely suffer. If it’s too good to be true...

PHRubin Loc: Nashville TN USA

It also can reduce the effective wide-open aperture to the point that your camera can't auto-focus. Most cameras cannot auto-focus at f/8 or below, some can get as low as f/8 but not lower. By lower I mean smaller openings like f/11 or f/22.

robertjerl Loc: Corona, California

rwags18 wrote:

Interesting. My thought is that the image quality would severely suffer. If it’s too good to be true...

...it is the PR or sales department - or a politician.

robertjerl Loc: Corona, California

PHRubin wrote:

It also can reduce the effective wide-open aperture to the point that your camera can't auto-focus. Most cameras cannot auto-focus at f/8 or below, some can get as low as f/8 but not lower. By lower I mean smaller openings like f/11 or f/22.

Several of the mirrorless can AF at f/11. And a few special use, one at a time build very expensive cameras can AF even lower. But you only find those in observatories, labs etc.

Blurryeyed Loc: NC Mountains.

rwags18 wrote:

I’ve recently came across an article in which it states that two Canon extenders, the 1.4x III and the 2.0x III, can be stacked, with the use of a 12mm extension tube, and not lose the auto-focus feature. It states that if you use a piece of insulated tape and place it over the contacts of the 2.0x extender, that will eliminate the loss of auto-focus with the 2.0x extender. Has anyone ever done this? What is your opinion of how this would affect the picture, if any?

I seriously doubt that it will work, back in the day I stacked Sigma extenders but now have the Canon III's and they won't stack, my experience with tubes is that they severely limit focus to very close focus losing all ability to at any distance beyond a few feet, if you put tape over the contacts then you will lose electrical connection with the camera body. I certainly would not spend money only to find out that it does not work.

rwags18 Loc: Oregon

Blurryeyed wrote:

I seriously doubt that it will work, back in the day I stacked Sigma extenders but now have the Canon III's and they won't stack, my experience with tubes is that they severely limit focus to very close focus losing all ability to at any distance beyond a few feet, if you put tape over the contacts then you will lose electrical connection with the camera body. I certainly would not spend money only to find out that it does not work.

Thank you. I appreciate it. It’s good to know. It makes sense that the extension tube would limit the camera’s focus. Thank you again.

Dan Thornton Loc: Corpus Christi, Texas

I have stacked a 1.4 and 2.0 extender with my 300mm lens and got usable results. I did it as an experiment and did not attempt it with small subjects like birds. I did not use an extension tube though and I did not tape any contacts.

BobHartung Loc: Bettendorf, IA

rwags18 wrote:

I’ve recently came across an article in which it states that two Canon extenders, the 1.4x III and the 2.0x III, can be stacked, with the use of a 12mm extension tube, and not lose the auto-focus feature. It states that if you use a piece of insulated tape and place it over the contacts of the 2.0x extender, that will eliminate the loss of auto-focus with the 2.0x extender. Has anyone ever done this? What is your opinion of how this would affect the picture, if any?

Maxis Gamez a photographer in Florida is know to use stacked tele-extenders with an extension tube in-between and then tacking on his 800mm lens. You might give him a jingle, his phone number and email are on his contact page of the web site linked to above.

cactuspic Loc: Dallas, TX

robertjerl wrote:

Several of the mirrorless can AF at f/11. And a few special use, one at a time build very expensive cameras can AF even lower. But you only find those in observatories, labs etc.

Actually, the Canon R5 can auto-focus at f/22, which is why they can sell an f/11 800mm lens and use it with a 2x converter, although I imagine the ISO would really have to be pushed.

rcarol

PHRubin wrote:

It also can reduce the effective wide-open aperture to the point that your camera can't auto-focus. Most cameras cannot auto-focus at f/8 or below, some can get as low as f/8 but not lower. By lower I mean smaller openings like f/11 or f/22.

Unless it's a mirrorless camera..............

rcarol

robertjerl wrote:

Several of the mirrorless can AF at f/11. And a few special use, one at a time build very expensive cameras can AF even lower. But you only find those in observatories, labs etc.

Canon claims the RF series of cameras can focus down to f:22. That is the resulting f-stop when you combine either the new 600mm or 800mm tele lenses with a 2X converter.

imagemeister Loc: mid east Florida

rwags18 wrote:

I’ve recently came across an article in which it states that two Canon extenders, the 1.4x III and the 2.0x III, can be stacked, with the use of a 12mm extension tube, and not lose the auto-focus feature. It states that if you use a piece of insulated tape and place it over the contacts of the 2.0x extender, that will eliminate the loss of auto-focus with the 2.0x extender. Has anyone ever done this? What is your opinion of how this would affect the picture, if any?

The version II Canon extenders can stack without an extension tube. Stacking the version III's with a tube will still allow infinity focus AFAIK. IF you have to tape contacts to enable AF, the AF will be very POOR - IF - at all.
and, of course the optical image quality will also suffer.
.

MtManMD Loc: Beaverton, Oregon

George Lepp, a long time Canon Pro and author, and also a fellow Oregonian, has used multiple teleconverters and long Canon lens for some excellent extreme telephoto shots. He's written several articles on it, so I'd suggest doing a search.