Canon Extender.

[IceCanAm]

Just asking. Is it possible to use a Canon extender EF 2X III on a Canon EF 70-300mm f/4-5.6 IS USM lens ?

Thanks in advance.

 

[KenC]

No. Just for reference, here's a compatibility chart:

Canon Extender EF 2x Compatibility Chart

 

[KmH]

KenC, it might help if you explain what the compatibility issue is.

 

[Bitter Jeweler]

I think Derrel answered this a while ago...You can use it on many lenses, but you limit your focal distance, both near and far. So you loose the ability to focus maybe 100feet away (if that) and no more focussing to infinity.

Did I remember that right, Derrel?

 

[Overread]

Bitter - I think you are mixing up extension tubes with teleconverters (its understandable as Canon calls their teleconverters "extenders").

To expand teleconverters (all brand designs) have a protruding front element, this sticks out in the fore of the lens mount. This creates a physical restriction on what kind of lenses can fit teleconverters. Typically your average 70-300mm lens often has a rear element that is quite far back and thus there is no space to fit the protruding front element of a teleconverter (even kinds like the pro series Kenko teleconverters which have about the smallest protruding front element).

 

[Bitter Jeweler]

Oops!

I guess I was confused by "extender" in the thread title, rather than "teleconverter".

 

[IceCanAm]

I thank you all.

 

[TCampbell]

Multiple the teleconverter factor by both the focal length AND the focal ratio. It's the last part that many people don't realize.

That means a 2x converter on a 70-300mm f/4-5.6 lens would effectively turn it into a 140-600mm f/8-11 lens. It's the f/8-11 that becomes the real problem. Auto-focus sensors work best at low focal ratios. Most work up to f/5.6 and maybe a shade higher. Very few cameras can use auto-focus at f/8 (and those that do won't focus as quickly.) Your 650D falls into the category of the majority... it wont focus at f/8. You'd have to manually the lens (I've never tried "live view" mode which uses contrast detection AF).

2x teleconverters are really intended to be used with f/2.8 lenses (which become f/5.6 lenses when the 2x converter is in use.)

 

[Tony S]

You can always cheat... use a 25mm extension tube between the TC and the lens, but you loose all auto functions with a few exceptions.

BTW, the term extender is what Canon uses on their web site for the teleconverters. You have to be specific between an extender and an extension tube.

EF 2XII Extender
Compatible Products >
Price: $429.99

 

[Overread]

You can always cheat... use a 25mm extension tube between the TC and the lens, but you loose all auto functions with a few exceptions.

Actually if you use a good quality extension tube (such as a Kenko brand extension tube) then the tube will have the metal contacts which means that you retain full lens control - all your aperture and auto focus remains. What will always happen though, is if you use an extension tube you lose the infinity focusing and reduce the minimum focusing distance of the lens. This is important as you can end up being only able to focus a few feet to maybe a few inches from you (the amount varies depending upon the lens and the amount of extension you add with the tubes).

So whilst the extension tube lets you mount a teleconverter, the loss of longer distance focusing means that in most situations you'd defeat the point of the setup if your intent was greater reach (it is, however, a very valid method for boosting magnification when shooting macro and close up photography).