extension tubes

hi all, i am researching extension tubes for my camera and would like some input from all the great members on this site. i have considered just buying a macro lens but i like the idea that tubes will convert any lens into a macro lens. not to mention the tubes are quite a bit cheaper than a lens alone. my questions are about the auto focus and exposure ability with the d 3100. i know i will need to buy tubes that have the contacts for the electronics for focus. any tips would be nice and any particular brands everyone likes. thanks

Google compatibility..

Extension tubes are just that. No glass, no electronic contacts, just hollow tube to allow your lens to focus much closer.

Here is what I have just to give you an idea. Nikkor 135mm f2.8 Ai lens and a Nikon PK 13.


Nikkor 135mm f2.8 Ai and Nikon PK13 extension tube by gqtuazon, on Flickr

As long as you get a chipped tube set, it matters not really. There's nothing in an ext. tube that can really choke things up.

Then only caveat would be that you're trying to turn a regular lens into a macro lens. True macro lenses ( this doesnt include the pathetic marketing crap where they say a lens is macro when what they actually means is its just ' CLOSE FOCUS ' ) are built differently to a regular lens. Macro lenses raison detre is incredible sharp photos at rediculously close focus @ 1:1 image size on the sensor. Regular lenses are not built that way, but having said that, you can get some superb images using non macro lenses with tubes or by other means, like reverse mounting something like a 28mm prime

The highest rated tubes seem to the Vivitar VIV-EXT-N 3 Set Extension Tubes for Nikon.
Amazon.com: Vivitar VIV-EXT-N 3 Set Extension Tubes for Nikon: Camera & Photo

There are other models made by Cowboy Studio and Zeiko's also.