You can blur the background a couple of ways. In a static image simply reduce the depth of field (DOF), this is achieved by selecting a wider aperture, or lower "f" number. If you focus on your primary subject, and shoot wide open (lowest "f" number), in aperture priority, your background should be blurred. The degree of the blur effect depends on the relative distance of your subject to the background and the focal length you select, and the lens' maximum aperture. For example focusing on someone, standing about 2 feet away from some bushes in the backyard, and shooting with an 18-105 set at 18mm and f/3.5 will show little to no blur in background. However, shooting that same subject, moved to about 10 feet from the bushes, and shooting with an 85mm lens at f/1.8 should render the background quite blurry. I hope this is helpful for you. Best regards.

I would not recommend it unless you have a lot or are planning on purchasing a lot of "D" lenses. Even if that is the case, I think you should consider the D90 or D7000 over the D80. The D3100 is a fine camera and is much lighter than other bodies. The D80 is a great model with a bright viewfinder and an in-body motor, but it actually gives up some IQ to the D3100 and can't do video. This is because it is a different generation body.

It might help to understand the Nikon DX dSLR lineup:

1. D40x/D60 -> D3000 -> D3100 : Entry class DX dSLR
2. (D60?) -> D5000 -> D5100 : Recently characterized by the flip down LCD for live view and videography
3. D80 -> D90 -> D7000 : Enthusiast model. Adds an in-camera motor to AF older lenses and a bright viewfinder
4. D200 -> D300(s) -> (nothing) : Professional DX dSLR. Adds an even more expensive viewfinder, all-metal construction, and better performance. Metering still works on older lenses.

My personal history might help. I started with the D70 (two generational predecessor to the D80), jumped to the D200, and then left for the Nikon FX line (Nikon D3). To be honest, the D200 is more than enough camera for me today, and the image quality out of your D3100 would blow my D200 out of the water!

Why not give it a little more time. As you graduate up in Nikon bodies, you gain more physical control over the camera and better performance (more fps and brighter viewfinder), but you lose a lot of the automation features (guided mode, scene modes, etc). Besides, any lenses purchased for the D3100 will still be excellent on a future DX body. (I still shoot my DX lenses on my old D70 which I use for infrared photography).

If you find the menu-based features of the D3100 confining, never use the guide mode, and want more direct control, you can purchase a D5100, D7100 or sequel to the D300 and sell your D3100 once you get used to the extra weight and know you aren't giving anything up in performance.

I hope this helps and good luck with your Nikon camera, no matter what model it is!

I believe all Nikon cameras are produced in Japan, or various other foreign countries...
The USA Warranty, is for United States and prepared for USA...
The "gray market" cameras from my understanding are models made for other countries, that get improved here to USA , but they do not carry the USA warranty, and I have heard that some parts are missing, accessories etc...
This is my understanding and I believe the Models here on this site are all USA warranty models,
other companies will sell "gray market" to anyone, but beware.. if you find major price difference in models you can be sure this is due to "gray naket" vs USA Warranty models...

Look at the D3200 or the D5100...very awesome cameras with lenses for under 1,000$

I don’t believe you can , since they send quick charger with camera...

I believe it does not come with lens, if it doe sit will usually say so in product description or in the Tech Specs section ...

Specs say 20 minutes maximum...

Yes, the entire CLS system is supported by this camera...

Hi
Unless it states here that it is a kit camera, it is body only...
Adorama or b&H are both authorized dealers for Nikon, you could look at their sites and immediately have all the info you need...
Just be sure you are looking at USA models and lenses and not "gray market"... there is a price difference but that is not all that is different...

I would try using you continuous focus and switch to closest subject priority, and I’m not sure if your cam has same as my D2X , but i can select which sensors i want to be tracking closest subject, i.e,: vertical sensors or horizontal...
I find myself never using closest subject focus, but i mainly shoot larger cars, race cars on track so to keep sensor on the car is easier than to keep it on a dog...

Try all your settings and see, i bet closest subject will work for you better...

Depending on how slow your shutter speed is, I;m sure it will impact the FPS if its real slow...