Nikon tech question.
 

Thought I'd try the brain trust here:

I recently bought a TC-20e III (2x teleconverter), and my camera does not recognize it. Also, autofocus hunts from focussed to infinity and will not lock (tried all modes). The camera and lens compatability charts say it should all play nice together. The google searches say they should all play nice together. I have the same question in to Nikon's service dept, with no reply as of yet.

Camera: Nikon D4
Lens: 70-200 f/2.8 VRII

What I expect to see in the camera display is a reduction of aperture at maximum from 2.8 to 5.6, and the EXIF data to be corrected, doubled focal length, corrected aperture, and most important, I'd like the darn thing to auto-focus.

Any suggestions?

1. Did you try it with another lens? Same results?

2. You said you tried all modes of autofocus - can you clarify? Have you tried single-point focus? If you are using multi-point, your edge focus points my be compromised by the teleconverter.

-Z

1. That's my only compatible lens. It recognizes the lens as if there is no teleconverter installed.

2. Yes, have tried single point, with AF-S (single shot). I was able to get one lock after pre-focusing manually, but not repeatable.

Auto focus may not work when min aperture is only 5.6.

No, my D4 focuses up to f8.
Try cleaning all the contact points- camera, Tc, and lens. Over the years my TC's occasionally hiccup, and cleaning all the contacts usually takes care of it.
Good luck
Gary

Could it be that you need to update the firmware for your camera?

Try cleaning the contacts.

Just tried the 70-200 f2.8 with the above tele-extender and D800e. No problem with autofocus at f5.6 or at f40.

If cleaning the contacts doesn't work, try posting at Nikon Forum - FM Forums

Puzzling. I know they're not the same beasts but my D3 autofocuses beautifully with the TC-17 and 70-200 f/2.8 VRII even when I use ND filters and/or stop down to f/8-f/16. The simplest explanation may just be that it's defective - bad connection most likely as there are no electronics in the TC as far as I know. But I'd check on firmware updates as suggested above, too.

You have an effective reduction of light with the TC, which will impede your focusing performance. This link will explain the partial reduction of focus points according to maximum aperture and teleconverter strength.

Your lens combination does work; just with a lower hit rate and worse 3D tracking. I've shot with the same lenses, but a D800E body. There's a reason the expensive glass is expensive. :)

If you find the performance unbearable, you might try the 1.4 TC. Only about 5% loss of sharpness and, of course, much better auto-focus due to greater light transmission. You might need to use a different lens to achieve similar reach, but if the choice is between blurry subjects close-up and sharp subjects far away...