Tamron 2X N-AFs not working

<p>I'm wondering if anyone here has had an issue using an auto focus Tamron 2X tele-extender on Nikon? It is a 2X N AFs BBAR MC7.<br>

I picked it up used, and have not been able to get it to work on my D200 body with either a Nikon Dx lens nor a standard 35mm Nikkor AF lens. I guess it is possible that the continuity between one set of contacts and the other set is broken. Has anyone had an issue like this? To be clear, it mounts up fine, it just will not focus. There is no manual lever or switch built into it to override autofocus.<br>

Thanks in advance!<br>

DG</p>

<p>Hi David. With the proviso that I've not used this

precise teleconverter, <a

href="http://www.nikonians.org/website/var/assets/file

s/nikonians-teleconverter-compatibility-chart.pdf">this

chart</a> suggests that the Tamron teleconverter you

mention probably only supports autofocus with AF

(screw drive) lenses, not AF-S or AF-I lenses. I've not

peered closely enough to count the contact pins, but I

believe them. Are both your lenses AF(-D)? If you've got

AF-S lenses, as most DX lenses are, I suspect you're

stuck with manual focus unless you go for an SP Pro

Tamron converter (or another brand).<br />

<br />

I assume you only mentioned the lack of a switch in case

we were going to tell you to look for one - but if you

actually can't manually focus, there should be a switch

on the lens (which will stop any attempt from the lens to

focus - which shouldn't really matter with AF-S) and one

on the body (CSM) by the lens mount, which will

disengage the AF screw on the body from the

teleconverter (you can see it retract if you look at the

lens mount). If you can't manually focus then, it shouldn't

be the teleconverter's fault!<br />

<br />

If you're using an AF-D lens and the camera's autofocus

is engaged, does the camera see the lens (identify the

aperture correctly)? If so, I'd hope the electronics are

okay. Autofocus should be mostly mechanical, with a

pass through screw, if the camera thinks it's got a lens

on it. Might something be jamming the screw drive? (I'd

try turning it manually.)<br />

<br />

Just to bring it up, I assume the 35mm lens was just a

test (this is an odd way to get a slow 70mm lens). If

you're planning to use this with a longer DX lens, be wary

of the aperture. Many Nikon bodies, including the D200,

only like to autofocus given f/5.6 or faster, though they

may kind of work a bit below this. Bear in mind a 2x

teleconverter reduces the lens speed by two stops. If

you're thinking of putting this on an f/5.6 zoom, I doubt

you'd get reliable autofocus even if everything else

worked, because the camera would be trying to focus at

f/11. You're likely better off blowing up the image in

software, or biting the bullet on a longer lens.<br />

<br />

Sorry about the delayed response, but I hope that's some

help if you've not already resolved your problem. Good

luck.</p>

<p>I have used an MC4 with a D70s, and it tries to autofocus, but usually fails.</p>

<p>For lenses that use the motor in the camera, there are 2:1 reduction gears in the converter. Since the 2X converter also changes the effect of focusing by 2X, that helps. That is, the effect that AF is looking for happens faster with a 2X converter. As noted, with the 2 stop aperture reduction, there is less less signal with the smaller aperture.</p>

<p>With the motor in the lens, there is no reduction in focus speed. It overshoots, then goes back and overshoots the other way. Constantly trying, but never getting there. But it does try.</p>

<p>Maybe with the MC7, they just turned it off. </p>

<p>I also have a 1.4X converter, which I think does autofocus, but haven't tried it much. The effect might be small enough that it works.</p>

<p>With the</p>