OK, I did exactly what Eric did, only on my D4. There is very minimal rotational slop between either the TC-14EII and the 70-200mmf/2.8VRII nor the D4 body. My results were the same as Eric.

Of note, when the preview button is pressed and held, the aperture is varied by the sub menu control in Manual mode, and then the preview button is released, about a half second later the lens makes a small noise, which is the image stabilization system shutting down I believe. If this does not happen on your combo on the D800, it would suggest an electrical connection problem most definitely IMO.

Eric said:
@dgrPhotos - Okay. I took my D800E and attached my TC-14EII and then I attached the Nikon 70-200 f/2.8 VRII to the TC. The viewfinder is nice and bright. If I press the DoF preview button, the lens stops down. If I hold down the DoF preview button and change the aperture, I can hear it click and see the change of brightness in the viewfinder.

I then tried the 300 f/2.8 VRII. Same thing, it works as expected.

In other words my TC-14EII seems to work fine on my D800E.
There is a small amount of rotational slop between the lens and the TC.
The TC seems to fit tightly to the body with virtually no rotational slop.

Thanks for the info. Mine will go back.

@dgrPhotos - Okay. I took my D800E and attached my TC-14EII and then I attached the Nikon 70-200 f/2.8 VRII to the TC. The viewfinder is nice and bright. If I press the DoF preview button, the lens stops down. If I hold down the DoF preview button and change the aperture, I can hear it click and see the change of brightness in the viewfinder.

I then tried the 300 f/2.8 VRII. Same thing, it works as expected.

In other words my TC-14EII seems to work fine on my D800E.
There is a small amount of rotational slop between the lens and the TC.
The TC seems to fit tightly to the body with virtually no rotational slop.

Eric said:
I'll check in a few hours and see what my D800E does as I have the TC-14E. I'll let you know.

Cool, I haven't seen any reports of this so I'm assuming it's not common. Let me know what you find out.

Okay this is getting stranger. I did play with the sequencing when the TC and then the lens goes on and it didn't make a difference.

What I did was shine a light through the VF so I can actually see the blades better when putting the lens on. What happens is the aperture blades are opening during the mounting process. As you twist you can see the blades open. When I mount the lens once in a while I can see the aperture blades opening up. Give the lens a little shake and the aperture blades close up! This behavior happened regardless if I had the TC already on the lens and was mounting it to the body or if the TC was mounted on the body and I was mounting the lens to the TC. Exact same thing! Once in a while the blades would catch and then just close up.

I do the same test, shaking and all, on the D5100 and nothing! It working perfectly! It sounds like a mechanical issue but it doesn't happen when mounting on the D5100. This is strange!

I'll check in a few hours and see what my D800E does as I have the TC-14E. I'll let you know.

Just a thought... you are putting the TC on the lens first, then the lens and TC on the D800, right? And, taking the combination off the D5100 and then mounting it directly on the D800 is when the D800 is not allowing the aperture to reopen, correct?

Is there anything possibly pressing on the aperture preview button, either during the mounting process or afterwards? Or is the preview button pressed somehow before the lens is mounted?

And the battery is fully charged? Has the lens been mounted when the camera is turned on?

Well, these are what goes through my head.... Somehow, if other lenses work on the D800, and the combination of the TC and lens works on the D5100, this sounds like some setting issue. I do not think the TC has any real function except as a conduit of information, electrically. But, as it works on the one body, it should work on the other.

Just got my Nikon TC-14E II and it's not working with my D800.

With Nikon lenses the aperture blades close until you mount it on a camera and turn it on. Once you do that it will open the aperture to it's widest settings, that part is common amongst brands. When using my TC-14E on the D800 the blades never open on the lens. Same results with my 70-200 and 300mm lenses. With my D5100 it works just like it's suppose to, not a single issue.

I went ahead and reset my D800 to default settings and cleaned the contacts in the body but the issue remains. My D800 works perfectly without the TC-14E. My D800 also works perfectly with the TC-20E III.

Anyone see something like this before?