Hello: Have been testing my new D7100 in the field and noticed an anomaly with my Tamron Lens and Auto focus. I am using a Tamron DI 70-300 no OS. Lens was at 300 mm and wasn’t locking on many targets in my back yard. I was not getting the focus indicator, just right of left arrow. Sometimes it would work as advertised.. I then switched to my Nikkor 70-300 AF 1:4-5.6 G lens (Earlier kit lens, w/o OS,) and targets were locking in. With two lenses with similar characteristics why would the Tamron give this grief? Camera was set to AF-C 9 points and 5 points for test. Is this a Problem in the lens?
Many more people better qualified than I may respond but I've seen where some third party lens have to be "programmed" for different bodies. Since the 7100 is new perhaps the lens isn't fully connecting with the body. If so, you will need to send it in for work that will make it compatible with the 7100. Just a thought. Good luck.
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Was the focus point in the center? Did other focal lengths work as expected? If you were not using the center FP, since your lens has a widest aperture of 5.6, it could have been just not enough light and contrast at f/5.6 to focus reliably. If you were using the center point and it was not focusing, was the focusing target a good one, one with edges, contrasts? Focusing on a black dog in shadows might not have the distinct edges to qualify as a suitable focus target. If you are sure the focal point was in the center and a good target, it is possible that the distance information transmitted from the lens to camera was wrong or not connecting. That is why some 3rd party lenses have to have their mpu chip updated to be compatible with the newest cameras. That is not uncommon to have new models of cameras and older lenses from 3rd party companies needing this update. We heard of it most often about Sigma and the company is very good and quick in updating lenses. Usually they will not focus at any focal length which is why I asked whether it focuses at shorter focal lengths. Stan St Petersburg Russia
I did have center point Focus and tested at different focal points as I did the Nikkor. My gut feeling at first was the targets, which were large trees in a stand of others. I was focusing on the bark of a pine with a large diameter. Also on a white birch.The Nikkor was more apt to lock than the Tamron. I had plenty of light. Shutter speed was I recall around 2000 with F stop of F11'ish. Didn't shoot a pic as I was trying to test the AF function of the camera. I did fire an email to Tamron to get their thoughts
I talked with customer service at Tamron today, and they told me they did not have a body to test it with, nor a D7000, nor a D800, or D600. Said if I wanted to send the lens in along with my body (are you crazy?) they would test it. I also asked about my other Tamron lenses @ 18-270 and the 90mm macro and the rep suggested that I run some tests with them. Maybe Ken Rockwell is correct!!!
You have encountered an issue with third party lenses and Nikon bodies...compatability. The third party companies have to reverse engineer for any new Nikon products. Nikon doesn't share information with them. Conversely Nikon designs their lenses to be compatable with current and older bodies (within reason).