D3100 won't stop trying to focus

Triqks

I'm sorry if this question has been answered a bunch of times before, but I just can't seem to find the answer. I'm attempting to shoot video of me sitting down and talking, however, whenever I sit down in front of the camera, it starts to focus. As soon as I start speaking or move my arms, the camera will attempt to refocus and it won't stop. This causes the video to blur and focus as the camera is attempting to find the sweet focus spot. I want my camera to find focus when I sit down in my chair and never refocus again since I won't be moving from my spot. How can I do this?

houghs

Try to focus the camera into the spot where you are sitting and then switch the lens into manual focus.

PBked

Make sure your lens is set to an aperture which gives you enough depth of field. The reason it is constantly trying to focus is probably because you have a shallow depth of field and when you move you are moving in and out of the said depth of field.
I agree with @houghs when he advises manual focus. Get someone to sit in your position and manually focus on the eyes. With a good depth of field, you should get the result you want.
Good luck, PBked