I am using the D7000 with a Sigma 18-200
For some reason the autofocus won't lock at all. When I push the trigger button down slightly it the focus moves back and forth never finding the right point.
I switched the lens to my D90 and there is no problem so I assume it is not the lens.
Also the assist light does not come on and it looks like in the menu that it is set for it to come on.
I am about to bring it to a repair shop and thought I would post here first.
#1. "RE: no auto focus" | In response to Reply # 0
These cameras are complex these days. You should give us a rundown of what you've tried to far.
When the AF-Assist light doesn't come on when you think it should, it's for one of two reasons. Either you have AF-C selected, or the focus point isn't centered. Page 210 of the English D7000 manual lists the conditions needed for AF-Assist to work.
An off-center focus point will cause this problem if there's nothing under the focus point to lock onto. So my suggestion is to check your selected focus point.
#2. "RE: no auto focus" | In response to Reply # 1
>When the AF-Assist light doesn't come on when you think it
>should, it's for one of two reasons.
It's more complex than that. For example, AF-Assist is not available in certain scene modes. Check pages 210, 273 and 292-293 in the manual for a full rundown.
#3. "RE: no auto focus" | In response to Reply # 2
In addition to the AF-Assist light settings, if the Sigma is older, it may not be compatible with newer Nikon's. Sigma will know which versions are and yours might need to go back to their service center to have is chip replaced. Sigma can do that quickly and does not charge for it.
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