Shallow Depth and Open depths have vast differences. Unlike Open depth, Shallow depth of field is when there is only a small amount of area in an image that is focused. With Open depth of field you are able to change the setting on your camera allowing you to see better. An example of this, is how your eye has an iris that lets in the amount of light that is necessary. A camera has the same effect, it has its own iris.
We celebrate the dead because they deserved the best and happy death note a sad one. And the narrator think its interesting because we celebrate instead of being sad