Extension Tube Macro Ring for Nikon D3100?

Hi, I just received this product that I bought from stppo.com And after I put it on my camera, it is blurry and dark. I tried it with and without flash and tried every single ISO mode. It still comes out blurry and dark. I would like to know how does it work? I need help using it because I see people using extension tube and pictures comes out really pretty indoor and outdoor.

As you've discovered these things are not what they're cracked up to be. Did it come with an instruction brochure or manual? If so, read it.

I'm not sure if you are describing an extension tube or reversing ring. In either case, these are for macro work, and you can only focus a couple of inches from the lens.

the least expensive extension tubes, you have to manually focus the lens.

Some extension tubes do not have contacts in them so the lens can be controlled by the camera. Nikon "G" lenses requires them as there's no way you can control the aperture. If your photos are real dark, it's because the lens is at the minimum aperture.

If you paid less than $75 for the extension tubes, you bought the wrong type.

Extension tubes do work pretty well, but you have to buy the right ones and know how to use them.

Macro reversing rings will not work at all with a G lens. Your D3100 kit lens is a G lens.