7D + Sigma 100/300 + Sig x1.4 probs

Going to Duxford tomorrow & decided to micro adjust my 100-300 f4 + x1.4 extender ready for action

First prob I notice is that the 7D only shows the already microadjusted 100-300 when the extender is added, is this right can I only have one adjustment per lens regardless of extenders or not?

Secondly I've noticed that with the above combo on it will only auto focus about 50% of the time & when it doesn't find focus it seems to lockup & won't find focus on anything at any distance unless I move the focus ring myself slightly then its fine again until it doesn't find focus & the above startss again?

I have had the extender a few years so wondering if its chip (if it has one?) isn't quite right with the 7D as the combo is f5.6 so should still autofocus?

Have to say without the extender the 100-300 works beautifully & focuses everytime, was just hoping to use the 420mm

Is it a call to Sigma or something else?

Many Thanks,

Shelton.

Have you tried the tc with your 7-2 f/4 IS? Give that a try and see if it works...

Hadn't thought of trying that! Just did so & granted indoors/poor light but trying both they see to have problems.....

I'll leave it at home tomorrow & have a look using the 70/200 in good light & see whether it does the same

Thanks for the help

Shelton.

Does the extender have the extra pins that are needed to report it being there (on the lens side)? If not the lens wont know an extender is fitted and therefore the camera will not know either.

It worked ok on my 40D, now leaving for Duxford so will have a look/play tomorrow

Shelton.

It's just a myth, like the 60D...