70-200F4 VR does not focus

[nick_baker]

<p>Hello</p>

<p>I wonder if anyone has a solution to my current problem. This morning I decided to try extension tubes on by 70-200F4 VR. I mounted a 20mm Kenko extension tube between the lens and my D7100 body and everything was fine. The I tried the 36mm tube. From this point onwards the 70-200 lens has not focused. Both AF <em>and MF</em> are kaput. The MF ring turns smoothly in the normal way, but to no effect. The D7100 body focuses other lenses; the 70-200 VR does not focus on another body (D5100). I have cleaned the contacts, not that this would explain the failure of manual focusing.<br>

Any suggestions?<br>

thanks<br>

Nick</p>

[ShunCheung]

<p>The 70-200mm/f4 AF-S VR has two rings. The focus ring is the one towards the front end of the lens. If you rotate it manually and it feels smooth, could you look into the front of the lens and see whether the front element group moves forward and backward as you rotate the focusing ring? The very front element is not going to move, but the group immediately behind it should move forward and backward as you focus, automatically or manually.</p>

<p>Needless to say, any extension tube goes on the rear end of the lens. So it is very unlikely that adding an extension tube would damage the focusing mechanism. If there is some short circuit, it might damage some electronics or the AF motor, but I don't see how an extension tube could affect manual focusing.</p>

<p>Also check the position of the AF/MF (A/M, M) switch on the barrel.</p>

<P>

<IMG SRC="http://d6d2h4gfvy8t8.cloudfront.net/16800557-lg.jpg">

</P>

[mike_halliwell]

<p>Um, not wanting to damage anything, but do the tubes work OK on your D5100 and another AFS lens? Either the 20 or the 36. If you have a circuit continuity tester, I suppose you could do a pin > pin check.</p>

 

<blockquote>

<p>I mounted a 20mm Kenko extension tube between the lens and my D7100 body and everything was fine. <br>

</p>

</blockquote>

<p>As expected. They're just pass-through contacts, a missing pin contact or a short circuit should give you a error but not damage anything.<br>

<br>

The non MF could I suppose be a disconnect or failure in the AF/MF clutch mechanism. The focus ring would spin, but there's no physical connection between anything inside.<br>

<br>

Return to Nikon as a failed lens. </p>

 

[nick_baker]

<blockquote>

<p>If you rotate it manually and it feels smooth, could you look into the front of the lens and see whether the front element group moves forward and backward as you rotate the focusing ring?</p>

</blockquote>

<p>Thanks for the suggestion Shun.<br>

As expected, the lens elements do not move with the MF ring</p>

[nick_baker]

<blockquote>

<p><br /> Return to Nikon as a failed lens.</p>

</blockquote>

<p>Yes, looks that way</p>

[ShunCheung]

<p>Since Nikon introduced the 70-200mm/f4 AF-S VR in 2012, if the OP's lens is a Nikon USA version and he is the first owner, it should still be under the extended 5-year warranty. Just send it in for warranty repair. Most likely some screw/connection mechanism is disengaged. Don't mention the extension tubes. They should have nothing to do with the focusing mechanism; you just don't want to introduce unnecessary questions into the situation.</p>