Lock focus and lightning with Nikon D3100

Question

I am trying to shoot a video with perfectly white background with a similar setup as described here: http://www.gowallaby.com/how-to-get-a-white-background-in-video/

However, Im using Nikon D3100 instead of iPhone to shoot the video. I can't find a way to lock the focus and light settings as instructed in the article

Watch for a yellow box to appear and bounce twice, and then indicate that the focus and lighting are locked. You can now turn on your background lights and you’ll see that the background becomes bright white.

I assume similar result should be possible with Nikon D3100 as with iPhone. Any suggestions?

Answer 1

It's actually a lot easier to do on your Nikon D3100 or just about any DSLR than it is on an iPhone. The instructions quoted in the question are specific for the iPhone's camera.

All you need to do is use Manual exposure mode. Whatever exposure settings you select are locked in until you manually change them. If you're not sure what settings to use then put the camera in one of the automatic modes until you find the exposure you are looking for, then switch to M mode and select the same ISO, aperture, and shutter time.

The same is true for focus. Use autofocus to focus on your subject, then switch the lens to manual focus and the focus will stay where you set it. Or you can use the magnified Live View screen to carefully manually focus the lens yourself. If the camera is at an angle or moving around where gravity or other physical forces might cause the focus elements of the lens to drift a bit, use gaffer's tape to restrict movement of the zoom ring.

Answer 2

I got it working now by having the bright lights (used to cast light to the background) turned off and pressing AE-L/AF-L button to lock the exposure settings. I then turned on the bright lights and got the poor white background. The AE-L/AF-L button was set to AE lock (Hold) -mode.

There are probably many ways to achieve the same result. I'll try the other suggestions as well to get better understanding of the camera workings. Thanks for the hints!