Sounds like you’re using the cine camera actor in sequencer, which exhibits real world properties of a physical camera. You’ll need to adjust the depth of field through the focus distance property.
https://docs.unrealengine.com/latest/INT/Engine/Sequencer/HowTo/CineCameraActors/
Alternatively, you could just use a regular camera actor - instead of hitting the camera button in sequencer, you can just add a regular camera actor, add it to sequencer, and then add it to a camera cut track so that it will take the viewpoint of that camera in game.
https://docs.unrealengine.com/latest/INT/Engine/Sequencer/HowTo/TracksCameraCut/