D700/24-70 2.8 Lens malfunction?

Started Dec 18, 2011 | Discussions thread
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Plus24 Regular Member • Posts: 179
D700/24-70 2.8 Lens malfunction?

I was shooting a group portrait sitting two days ago with a D700 & 24-70 f2.8 combo. I shoot raw and manual exposure with custom white balance. I had a nikon sb800 on my hotshoe with 2 quantum T5d flashes on radio slave as off camera flashes. All was going well when suddenly my shots were all heavily overexposed. I checked to make sure my manual exposure settings had not changed. They had not.

I turned off the camera and back on again. I also turned off and on all flashes. The shots were still heavily overexposed.

I pulled out my back-up D700 and put the 24-70 lens on the second camera body. Same problem. The shots were overexposed at the same manual setting that had previously been exposing correctly.

I then pulled out my 24-120 f4.0 nikkor and put it on my back-up camera. Same manual settings as before. Perfect exposure.

I changed bodies so that my 24-120 f4.0 lens was now on the original D700 body when the malfunction had occurred with the 24-70 f2.8 lens. Now, with the 24-120 f4.0 lens attached, exposures were again dead on perfect.

I finished the shoot with the original D700 body on which the 24-70 had overexposed, but with the 24-120 attached instead of the 24-70. The rest of the shoot resulted in perfectly exposed photos.

This morning I tested both camera bodies and both lenses. This time I did not use any flash. I shot outdoors with available light.

The first picture I took was with the 24-70 f2.8. Heavily overexposed as it was during the portrait shoot.

I then shot another picture at the same exposure with the other D700 body but with the 24-120 lens. Perfect exposure.

Then I switched the lenses on the 2 bodies. Same manual exposure settings on both camera bodies. Perfect exposures now from both lenses. The 24-70 was performing correctly.

I then switched the 2 lenses again on the camera bodies. Same results -- good exposures on both.

My tentative diagnosis: Since the 24-120 always exposed correctly on both camera bodies, but the 24-70 exposed erratically on both camera bodies with the overexposure problem on both camera bodies, the problem must be with the 24-70 lens.

My guess is that the lens was not stopping down to the aperture set by the camera. A stuck aperture blade, possibly.

Another possibility is a contact problem on the 24-70 lens. I'm going to clean the contacts on the lens and see if I continue to have the problem. Since the problem is erratic, it will be hard to reproduce it at will. All may seem to be o.k. until it malfunctions again.

Does anyone have any other suggested diagnosis of the problem? I don't want to send it to Nikon repair until I have exhausted all possibilities of fixing the problem myself.

Thanks for your help.


Nikon D700
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