Re: New D3100 owners
What you are referring to is called Time Lapse (TL) Photography. You will need more like 400+ images to make a short video. One trick to making TL is having an intervalometer, which is not build into the D3100. If you do not have one, there is a work around and you have to be at the camera every time you want an image. You will need a stopwatch or a watch that shows the seconds (digital or analog). Set your camera up for the exposure you want and place it on the tripod. Also turn off the VR as it is on the tripod. If you do not have a remote shutter release, set the shutter delay to 2 seconds, so that when you press the shutter release on the camera, it has a chance to settle down. Note the time and press your shutter release. When the capture is complete, what the set amount of time you want, and subtract 2 secs, for the shutter delay. Press the shutter release again at the appropriate time, and repeat, repeat repeat.
You will need quicktime or even Windows Live Movie Maker works too, for compiling all your shots of the series into a video.