Incompatability 70-300L and 2x ext III

Hi All,
A friend has just purchased a Canon 70-300 L lens and a Canon 2X Extender III to use on her 50D.
However the pair will not work together.
I have just researched a Canon compatability list and it said they are incompatable.
Can any tell me why they are incompatable and is there a way to overcome the problem.
Cheers
Bob.

the lens is f4-f5.6 which will focus on 50d
add 2xtc an it starts at f8 which 50d won't be able to use to focus - it needs a 1d something body[not 1dx either]

you might be able to tape pins on lens and extend the range some with the 50d but i doubt that it will work on the long end

when you say incompatible, do you mean it won't physically mount, or it will but not work electronically?

70-300l will not work with canon ext.

The rear lens element on the 70-300L protrudes too far out of the lens and will hit the element on Canon Extenders, the only option are to use the Kenko extenders, such as this one:
http://www.adorama.com​/KN14XPEOSDGX.html

Using this extender will result in one stop loss of light, meaning the lens will only have f5.6-8 through the zoom range. AF can still work in well lit cases, but my understanding is that it is slower and possibly less accurate, and it will only work on center point. I have debated getting this, but I just got the lens so right now I am working with it as it comes and then deciding if I really need that extra reach. The lens is so sharp that you get a ton of "crop zoom" ability with still great looking images.

Using a 2x extender will result in 2 stops loss of light, meaning it will be f/8-11 through the zoom range and there will no autofocus at all.

Not sure why the red face, it is clearly listed on the website, every review of the lens mentions it, and the manual which you can download before buying the lens also states that it doesn't work with Canon extenders.

That said, the lens without any extender madness is fantastic and I am really enjoying mine.

I have used a Kenko 1.4x with the 70-300L. AF works on the 5D2, but it hunts. There is also some IQ loss, but results are still OK. In principle, AF and IQ should be better with the 1.4x than with the 2x because you loose light and have a higher magnification.

I use the Kenko 1.4/70-300L combo on my 5DII now and then. The 1.4 TC may affect the IQ slightly, dependng on the shot. I've had good success focusing outdoors, using the center (most sensitive) focus point and back-button focusing.

I just picked up the Kenko 1.4X converter this weekend and am seeing the same results mentioned above, but on a 7D - good success focusing outdoors (and somewhat indoor - tried it at the camera shop pre-purchase and it did well in bright fluorescent lighting).

the OP never asked about a 1.4 TC.

ed rader wrote in post #14730679
the OP never asked about a 1.4 TC.

Those of us who posted about the 1.4X tele were offering "a way to overcome the problem" (quote from the OP in post 1 above).

I finally got to check out my friends dilema today. Yes the 70-300L and the 2X extender do not physically go together. The protruding lens on extender fouls with the rear lens in the 70-300 even at maximum zoom.
However I tried my Kenko extender on the 70-300 and it fits and works perfectly. No doubt the image quality on the Canon extender would be superior but the results with this combination looked quite acceptable.
So all is not lost; my fiend is now going to buy a 400mm f5.6L prime lens to go with the Canon 2x extender and also purchase a Kenko 2x extender to go with the 70-300L.
Thanks for all your comments.

I hope your friend will not be to unhappy with the resulting 800mm f/11 !!! lens -> dark, manual focus....

You have to use 3rd party companies when you plan to use extenders outside the list of compatible lenses. I used a Tamron SP Pro 1.4x TC with my 50mm f/1.8 for example long ago (just to try it, never did use it again). Not possible with the Canon model.

You would need something like Kenko or Tamron TC to use with lenses you can't with Canon. But expect to lose AF over f/5.6

Sounds like she really wants one of these..

http://www.bhphotovide​o.com …other-of-All-L-Lenses.jsp

mike1812 wrote in post #14730660
I just picked up the Kenko 1.4X converter this weekend and am seeing the same results mentioned above, but on a 7D - good success focusing outdoors (and somewhat indoor - tried it at the camera shop pre-purchase and it did well in bright fluorescent lighting).

Have any examples you could post? I'm interested in this lens- but only if I could use it with a 1.4TC in a pinch on my 7D, and the results were decent. The IQ of this lens is so good on it's own, I'm hoping the IQ doesn't take a big hit when adding a 1.4TC..like the 70-200 II.