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06-08-2010, 01:26 PM   #1
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Teleconverter affecting focusing of other lenses?

I've just bought the Sigma 100-300mm f4 lens and 1.4x teleconverter and early shots are extremely impressive. However, after turning my K7 off, removing the teleconverter and lens and putting back on my old (~10yrs) Pentax 80-320mm lens this one will no longer focus (manual or AF).
Other lenses (Tamron and Pentax, somewhat newer lenses) work fine. But I am a little concerned about putting a lens on straight after using the teleconverter- I don't want to lose another lens.
Has anyone experienced anything similar- is it safe to use a lens on the camera straight after having used a teleconverter (having switched the camera off of course to replace the lens)?
Anyone any idea about the old lens which no longer focuses on any camera?

06-08-2010, 03:23 PM   #2
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That is interesting. I'm assuming that your 1.4x supports AF, because I have a MF TC and have removed it dozens of times, attached both old and newer lenses immediately (sometimes I have even forgotten to turn the camera off) and have never had a problem. This could be due to the fact that I have no electronic connections like you do for AF. Although I have heard of some people actually shorting out the connections by accident (cannot tell you the reason why that happened though) but that would still not explain why it will not MF. Your lens not MFing sounds like a problem with the lens itself and not the camera. Can/have you tried to put the 80-320 on another camera and see if it focuses there?
06-08-2010, 03:23 PM   #3
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Could you clarify your statement: "However, after turning my K7 off, removing the teleconverter and lens and putting back on my old (~10yrs) Pentax 80-320mm lens this one will no longer focus (manual )" ?

If you use MF, how come you cannot focus manually with the lens itself ? I would not comment on AF, but I am puzzled by the un-ability to MF. Like any MF lens, ou should be able to focus manualy the lens and get focus confirmation in the view finder.

Do you mean that, in MF, you cannot get the green light for focus confirmation in the viewfinder of the K-7?
06-09-2010, 09:31 AM   #4
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More than likely, there is something wrong with your 80-320 if all your other lenses still work fine. If it won't manually focus either, then something inside is broken. It probably has nothing to do with the TC and the Sigma.


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