Rumors > Lenses

70-300L AF IS goes *CLUNK!* (??)

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RustyTheGeek:
Some of you may remember my little poll a while back asking what to replace my 70-300 IS EF lens with after a barter trade with a buddy.  Well, I finally did the deal and I decided to get the 70-300L.  So now I have a nice Thinkpad X301 all tricked out (from the trade) and a new 70-300L.

What's interesting is this...

-  Slap that 70-300L on the 5D3 and point it all over the place, AF performance is fast and smooth, fairly quiet and nice.
-  Add a Tamron 1.4x TC (140F-CA) and the AF slows a bit.  Not unexpected.  Still works pretty good.  HOWEVER...

... when the TC is attached, the IS tends to JUMP from time to time and makes a CLUNK NOISE.  You can feel the clunk too.  It still autofocuses on the target but the IS going CLUNK is weird.  I haven't been able to detect a clunk or jump when the TC isn't connected.  Anyone have some thoughts?

I've had the Tamron TC for quite a while and from what I have read around this forum, the Kenko 1.4X DGX is (I guess) the ideal TC but I don't necc want to buy another TC.  Anyone have a Tamron 1.4X TC like mine and like it just as much?  Curious how they compare.

Marsu42:
Good luck finding anyone with the Tamron tc combination, I just can say that the 70-300L+Kenko 1.4x tc combination never goes *clunk!* on the 60d - in contrast to the very noisy 100L hybrid IS where a very frightening *eeek!* sound is common when pointing the lens down or up :-o

RS2021:
70-300L is a quality Canon zoom with a growing reputation...get it off the Tamron TC....particularly if we are talking jumping and noises.  :o

RustyTheGeek:
Yeah.  I started this thread for two reasons...

-  Get opinions/reactions from others with regard to the anomaly
-  Inform others in case this truly is a possible hazard to the lens

I don't see how a TC could cause damage (or change the AF mechanism) but I guess you never know.  I'm glad to hear someone has used the Kenko successfully.  I'll consider obtaining that one perhaps after I see some more posts.

I've never had a problem with this TC before on any other lens I've used it with.

wickidwombat:
it could be the 5D3 and the tamron
I know the Kenko 1.4 and the 5D3 are a bit wierd for example if i stack the kenko 1.4 on the canon 2x and the 70-200 f2.8 II then its fine on the 5Dmk2 but on the 5Dmk3 the aperture flicks wildly between f5.6 and f8

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