http://www.nikonchat.com/nikon-d5100-motor/
Tell me pros and cons of Nikon D5100 and D3100. More emphasis on D5100.?
They also tell me if Nikon plans to launch any new camera so close year or a little more expensive these two cameras? > What does the lack of focus motor mean? how bad and how a buyer D5100 to deal with it? > What is the ferrite core attachment? What is its use? Thanks 
The Nikon D5100 is a fairly new and probably will not be replaced this year. Now some comments quite amazing and is definitely a good camera market design for the novice. http://www.dpreview.com/reviews/nikond5100/ http://www.kenrockwell.com/nikon/d5100.htm The entry level Nikon does not have an autofocus motor in the body, but depend on an auto focus motor goal. So are most compatible with Nikon AF-S, but manual focus in all AF lenses nikon af-d. Before that concerns you, be aware that Canon DSLR each is in the same boat. No built-in AF motor and requires AF motor in EF and EF-S. Here is a list of the many objectives (growing every month) of all compatible lenses. http://en.wikipedia.org/wiki/List_of_Nikon_F-mount_lenses_with_integrated_autofocus_motors ferrite cores are connected to cables suppress high frequency noise in electronic signals. I have had on other cables connecting different devices.
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