# What will the new mk. IV Canon Extenders have



## K-amps (Feb 8, 2012)

This is no rumor on extenders but... what would you like to see?

Some of Canon's new lenses are internal focussing, so that their rear elements move. E.G the 70-300L is not compatible with the 2x 1.4x mk.III's since the rear element comes out a bit and can hit the moving element of the lens that is mounted.

Will Canon fix this and increase extender compatibility? Or will they not increase barrel length since it makes long lenses heavier and longer yet ? I am asking since I want the 2x with my 70-300L, but they are not "compatible" under AF.


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## Gothmoth (Feb 8, 2012)

> What will the new mk. IV Canon Extenders have



you mean in 3-5 years?


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## iaind (Feb 8, 2012)

A whopping great price tag


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## K-amps (Feb 8, 2012)

Gothmoth said:


> > What will the new mk. IV Canon Extenders have
> 
> 
> 
> you mean in 3-5 years?



Yes... it perplexes me that the made mk.iii's with no regard to the internal focussing lenses they have been making lately that have moving rear elements.


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## Marsu42 (Feb 12, 2012)

K-amps said:


> Some of Canon's new lenses are internal focussing, so that their rear elements move.



I'd like to know: What lenses have these moving rear elements except the 70-300L? 

I thought the incompatibilty would be due to marketing concerns and since (at least 2x) extending a 5.6 lens doesn't make that much sense anyway.


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## hippoeater (Feb 12, 2012)

Here's a link

http://www.bhphotovideo.com/FrameWork/charts/canon1_4xExtender.html


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## Jim K (Feb 12, 2012)

I wonder about manual focus on a 600mm f/11 lens ???


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## TexPhoto (Feb 12, 2012)

The rear element need not float to mean you cannot use a teleconverter. It basically just has to be in the way. Plenty of Canon lenses have the rear element in the way, but not floating.

Nikon and Canon make their teleconverters this way, and 3rd party manufactures do not seem to. I would asume Canon/Nikon do t for IQ reasons and 3rd party goes their way for cost/compatibility reasons. But I don't see this changing.


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